CN118146299A

CN118146299A - Cyclic peptides and compositions and uses thereof

Info

Publication number: CN118146299A
Application number: CN202410266907.6A
Authority: CN
Inventors: 丁文锋; 赵文豪; 观富宜; 孙新林; 肖玉; 彭晏
Original assignee: Shenzhen Weiqi Technology Co ltd
Current assignee: Shenzhen Weiqi Technology Co ltd
Priority date: 2024-03-08
Filing date: 2024-03-08
Publication date: 2024-06-07

Abstract

The disclosed cyclic peptide has a structure shown in a formula (I): cyclo- [ Gly-His-Lys-Lys ] (I). In particular to the cyclic peptides or salts thereof, or compositions thereof, and the use thereof in the preparation of compositions for caring for or treating skin or mucous membranes.

Description

Cyclic peptides and compositions and uses thereof

Technical Field

The present disclosure relates to the field of polypeptide technology, and in particular to a cyclic peptide and a composition thereof, and uses thereof.

Background

Collagen, which is the major component of the extracellular matrix (ECM), is produced by fibroblasts and provides tensile strength and structural support to the skin. With age, collagen production decreases and existing collagen is degraded, resulting in skin sagging and wrinkling. Elastin is another important ECM component that imparts elasticity and resiliency to the skin. During normal physiological processes, elastase participates in the remodeling of the ECM, helping to remove damaged elastin and promote new elastin production, whereas overactive elastase can cause excessive degradation of elastin, thereby compromising skin elasticity and overall structure. Hyaluronic acid is an acidic mucopolysaccharide which has an extremely strong water-retaining ability in the skin and can help maintain the hydration state and volume of the skin. Hyaluronidase is an enzyme capable of degrading hyaluronic acid, which affects the moisture balance and texture of the skin by regulating the decomposition of hyaluronic acid. The enhanced activity of hyaluronidase results in a substantial reduction of hyaluronic acid, disrupting the barrier function of the skin and accelerating the loss of moisture from the skin interior. Tyrosinase is a key enzyme involved in melanin synthesis, which catalyzes the conversion of tyrosine to dopaquinone, which in turn forms melanin. Melanin can protect skin from ultraviolet rays, and prevent DNA damage and skin cancer. However, excessive tyrosinase activity may cause hyperpigmentation, and pigment skin diseases such as freckle, chloasma, etc., occur, so that tyrosinase activity affects the uniformity of skin color.

In summary, collagen, elastase, hyaluronidase and tyrosinase all play important roles in maintaining skin structure and function.

Disclosure of Invention

The present disclosure relates to cyclic peptides, and compositions containing the cyclic peptides, having the effect of caring for or treating skin or mucous membranes, and the like.

In one aspect, the present disclosure provides a cyclic peptide of formula (I), or a stereoisomer thereof, or a mixture of its stereoisomers, or a salt thereof,

Cyclo-[Gly-His-Lys-Lys](I)。

The cyclic peptides of formula (I) of the present disclosure may exist as stereoisomers or as mixtures of stereoisomers; for example, the amino acids they comprise may have the L-, D-configuration, or be racemic independently of each other. Thus, it is possible to obtain isomeric mixtures as well as racemic mixtures or diastereomeric mixtures, or pure diastereomers or enantiomers, depending on the number of asymmetric carbons and what isomers or isomeric mixtures are present. In some embodiments, the structure of a cyclic peptide of formula (I) of the present disclosure is a pure isomer, i.e., enantiomer or diastereomer. In some embodiments, the cyclic peptide of formula (I) of the present disclosure has the structure of the L-isomer.

The present disclosure also includes all suitable isotopic variants of the cyclic peptide of formula (I). Isotopic variants of these cyclic peptides of the present disclosure are understood herein to mean such compounds: wherein at least one atom is replaced with another atom of the same atomic number within the cyclic peptide of the present disclosure, but the atomic mass of the other atom is different from the atomic mass normally or predominantly present in nature. Examples of isotopes that can be incorporated into the cyclic peptides of the present disclosure are: those of hydrogen, carbon, nitrogen or oxygen, such as ² H (deuterium), ³ H (tritium), ¹³C、¹⁴C、¹⁵N、¹⁷ O or ¹⁸ O. Specific isotopic variants of the cyclic peptides of the present disclosure (particularly those into which one or more radioisotopes have been incorporated) may be advantageous, for example, for examining the mechanism of action or distribution of active compounds in vivo; compounds labeled with ³ H or ¹⁴ C isotopes are particularly suitable for this purpose due to their relatively simple producibility and detectability. In addition, due to the greater metabolic stability of the compounds, the incorporation of isotopes (e.g., deuterium) may yield particular therapeutic benefits, such as increased in vivo half-life or reduced amounts of active agent required. Isotopic variants of the cyclic peptides of the present disclosure can be prepared by methods known to those skilled in the art, for example, by methods further described below and in the examples, by using the respective reagents and/or corresponding isotopic modifications of the starting materials.

The term "salt" refers to a salt that is approved for use in animals, and more specifically in humans, including metal salts of cyclic peptides of formula (I), including, but not limited to: lithium, sodium, potassium, calcium, magnesium, manganese, copper, zinc, or aluminum, etc.; including salts of cyclic peptides of formula (I) with organic bases including, but not limited to: ethylamine, diethylamine, ethylenediamine, ethanolamine, diethanolamine, arginine, lysine, histidine or piperazine and the like; including salts of cyclic peptides of formula (I) with inorganic or organic acids including, but not limited to: acetic acid, citric acid, lactic acid, malonic acid, maleic acid, tartaric acid, fumaric acid, benzoic acid, aspartic acid, glutamic acid, succinic acid, oleic acid, trifluoroacetic acid, oxalic acid, pamoate (pamoate), gluconic acid, or the like; the inorganic acids include, but are not limited to: hydrochloric acid, sulfuric acid, boric acid or carbonic acid.

The synthesis of the cyclic peptide of formula (I) or a salt thereof of the present disclosure may be carried out according to conventional methods known in the art, such as a solid phase synthesis method, a liquid phase synthesis method, or a method of combining a solid phase with a liquid phase, and may also be prepared by a biotechnological method aimed at producing a desired sequence, or by controlled hydrolysis of a protein having animal, fungal, or plant origin.

For example, a method for obtaining a cyclic peptide represented by formula (I) comprises the steps of:

-coupling an amino acid having a protected N-terminus and a free C-terminus with an amino acid having a free N-terminus and a protected or solid carrier-bound C-terminus;

-elimination of the group protecting the N-terminal end;

-repeating the coupling sequence and elimination of the N-terminal protecting group until the desired peptide sequence is obtained;

-elimination of the C-terminal protecting group or cleavage from the solid support;

-condensation reaction is carried out on the free amino at the N end and the free carboxyl at the C end of the peptide sequence to carry out head-tail cyclization;

-elimination of the groups protecting the side chains.

In some embodiments, the C-terminus is bound to a solid support and the method is performed on a solid phase, comprising coupling an amino acid having a protected N-terminus and a free C-terminus to an amino acid having a free N-terminus and a C-terminus bound to a polymeric support; eliminating the group protecting the N-terminus; and repeating this sequence as many times as necessary to thereby obtain a peptide of the desired length, followed by cleavage of the synthesized peptide from the original polymer carrier.

The functional groups of the side chains of these amino acids remain fully protected throughout the synthesis with temporary or permanent protecting groups.

In some embodiments, solid phase synthesis can be performed by a pooling strategy (convergent strategy) of coupling a dipeptide or tripeptide to a polymeric support or to a dipeptide or amino acid previously bound to a polymeric support.

In another aspect of the present disclosure, there is provided a composition comprising an effective amount of a cyclic peptide of formula (I) above, or a stereoisomer thereof, or a mixture of its stereoisomers, or a salt thereof, and at least one excipient and optionally an adjuvant.

In some embodiments, the adjuvant is selected from the group consisting of: analgesic, agent that inhibits PAR-2 activity, collagen synthesis stimulator, agent that regulates PGC-1 alpha synthesis, agent that regulates PPARgamma activity, agent that increases or decreases triglyceride content of adipocytes, agent that stimulates or delays adipocyte differentiation, lipolytic agent or agent that stimulates lipolysis, lipolytic agent, adipogenic agent, inhibitor of acetylcholine receptor aggregation, agent that inhibits muscle contraction, anticholinergic agent, elastase inhibitor, matrix metalloproteinase inhibitor, melanin synthesis stimulator or inhibitor, whitening or decoloring agent, pigmentation-promoting agent, self-tanning agent, Anti-aging agents, NO-synthase inhibitors, 5 alpha-reductase inhibitors, inhibitors of lysyl hydroxylase and/or prolyl hydroxylase, antioxidants, radical scavengers and/or anti-atmospheric agents, active carbonyl scavengers, anti-glycation agents, antihistamines, antiviral agents, antiparasitic agents, emulsifiers, emollients, organic solvents, liquid propellants, moisture-retaining substances, alpha hydroxy acids, beta hydroxy acids, moisturizers, epidermohydrolases, vitamins, amino acids, proteins, pigments, dyes, biopolymers, gel polymers, thickeners, surfactants, softeners, binders, preservatives, anti-wrinkle agents, Agents capable of reducing or treating lower eye bags, keratolytic agents, antimicrobial agents, agents that stimulate synthesis of dermal or epidermal macromolecules and/or that inhibit or prevent their degradation, agents that stimulate elastin synthesis, agents that stimulate decorin synthesis, agents that stimulate laminin synthesis, agents that stimulate defensin synthesis, agents that stimulate chaperonin synthesis, agents that stimulate cAMP synthesis, agents that stimulate hyaluronic acid synthesis, agents that stimulate fibronectin synthesis, agents that stimulate deacetylase synthesis, agents that stimulate synthesis of lipids and stratum corneum components, ceramides, fatty acids, agents that inhibit collagen degradation, agents that inhibit elastin degradation, Agents that inhibit serine proteases, agents that stimulate fibroblast proliferation, agents that stimulate keratinocyte proliferation, agents that stimulate adipocyte proliferation, agents that stimulate melanocyte proliferation, agents that stimulate keratinocyte differentiation, agents that inhibit acetylcholinesterase, skin relaxants, agents that stimulate glycosaminoglycan synthesis, anti-hyperkeratosis agents, acne solubilizers, anti-psoriasis agents, anti-rash agents, DNA repair agents, DNA protectants, stabilizers, antipruritics, agents for treating and/or caring for sensitive skin, solidifying agents, tightening agents, restructuring agents, anti-stretch marks agents, agents that regulate sebum production, antiperspirant agents, agents that stimulate healing, Agents that assist healing, agents that stimulate re-epithelialization, agents that assist re-epithelialization, cytokines, sedatives, anti-inflammatory agents, anesthetics, agents that act on capillary circulation and/or microcirculation, agents that stimulate angiogenesis, agents that inhibit vascular permeability, venous tone agents, agents that act on cellular metabolism, agents that improve dermal-epidermal junction, agents that induce hair growth, hair growth inhibition or delay agents, fragrances, chelating agents, plant extracts, essential oils, marine extracts, agents derived from biological fermentation processes, inorganic salts, cell extracts, sunscreens, and organic or inorganic photoprotective agents that are effective against a and/or B ultraviolet light, or mixtures thereof.

The effective amount of the cyclic peptides of the present disclosure to be administered, as well as their dosage, will depend on a number of factors, including the age, the state of the user, the severity of the condition, the route and frequency of administration, and the particular nature of the cyclic peptide to be used.

By "effective amount" is meant an amount of one or more cyclic peptides of the present disclosure that is nontoxic but sufficient to provide the desired effect. The cyclic peptides of the present disclosure are used in compositions of the present disclosure at concentrations effective to achieve the desired effect. In some embodiments, the concentration is between 0.00000001% (by weight) and 20% (by weight) relative to the total weight of the composition; in some embodiments, the concentration is between 0.000001% (by weight) and 15% (by weight) relative to the total weight of the composition; in some embodiments, the concentration is between 0.0001% (by weight) and 10% (by weight) relative to the total weight of the composition; in some embodiments, the concentration is between 0.0001% (by weight) and 5% (by weight) relative to the total weight of the composition.

In another aspect of the present disclosure, a delivery system or a sustained release system is provided to achieve better penetration of an active ingredient, which comprises an effective amount of a cyclic peptide represented by the above formula (I), or a stereoisomer thereof, or a mixture of its stereoisomers, or a salt thereof, or a composition thereof.

The term "delivery system" refers to a diluent, adjuvant, excipient, or carrier with which the cyclic peptides of the present disclosure are administered, selected from the group consisting of: water, oils or surfactants, including those of petroleum origin, animal origin, vegetable origin, or synthetic origin, such as, and not limited to, peanut oil, soybean oil, mineral oil, sesame oil, castor oil, polysorbates, sorbitan esters, ether sulfates, betaines, glucosides, maltosides, fatty alcohols, nonoxynol, poloxamers, polyoxyethylene, polyethylene glycols, dextrose, glycerol, digitonin, and the like. Diluents that may be used in different delivery systems to which the cyclic peptides of the present disclosure may be administered are known to those of ordinary skill in the art.

The term "sustained release" is used in a conventional sense to refer to a delivery system of a compound that provides gradual release of the compound over a period of time. In some embodiments, the sustained release system has a relatively constant level of compound release over a period of time.

Examples of delivery systems or sustained release systems include, but are not limited to: liposomes, oleosomes, ethosomes, millimeter capsules, microcapsules, nanocapsules, nanostructured lipid carriers, sponges, clathrates, lipid vesicles, micelles, millimeter spheres, microspheres, nanospheres, lipid spheres, microemulsions, nanoemulsions, millimeter particles, microparticles or nanoparticles.

In another aspect of the present disclosure, there is provided a cosmetic comprising an effective amount of a cyclic peptide represented by the above formula (I), or a stereoisomer thereof, or a mixture of stereoisomers thereof, or a salt thereof, or the above composition, or the above delivery system or sustained release system.

In some embodiments, the formulation of the cosmetic comprises a cream, an emulsion, a water, an oil, a gel, a powder, a tablet, a mud, a patch, a film, an aerosol, a spray, a lyophilized formulation, or a nano-formulation.

In another aspect of the present disclosure, there is provided a use of a cyclic peptide represented by the above formula (I), or a stereoisomer thereof, or a mixture of stereoisomers thereof, or a salt thereof, or a composition thereof, or a delivery system or a sustained release system thereof, in the preparation of a composition for caring for or treating skin or mucous membrane.

In another aspect of the present disclosure, there is provided a cyclic peptide represented by the above formula (I), or a stereoisomer thereof, or a mixture of its stereoisomers, or a salt thereof, or a composition thereof, or a delivery system or a sustained release system thereof, for use in preparing a composition for anti-aging, repairing, moisturizing or soothing.

In another aspect of the present disclosure, there is provided a cyclic peptide represented by the above formula (I), or a stereoisomer thereof, or a mixture of stereoisomers thereof, or a salt thereof, or a composition thereof, or a delivery system or a sustained release system thereof, for use in preparing a composition for whitening, lightening skin color, removing stains and/or eliminating skin color unevenness.

In another aspect of the present disclosure, there is provided a cyclic peptide of formula (I) above, or a stereoisomer thereof, or a mixture of stereoisomers thereof, or a salt thereof, or a composition thereof, or a delivery system or a sustained release system of the above, for use in preparing a composition for inhibiting elastase activity, or for use in preparing a composition for promoting collagen production, or for use in preparing a composition for increasing skin elasticity and/or improving skin firmness, or for use in preparing a composition for promoting regeneration or healing of skin or mucous membrane, or for use in preparing a composition for repairing skin barrier, or for use in preparing a composition for inhibiting hyaluronidase activity, or for use in preparing a composition for inhibiting tyrosinase activity, or for use in preparing a composition for inhibiting melanin production.

In another aspect of the present disclosure, there is provided a cyclic peptide represented by the above formula (I), or a stereoisomer thereof, or a mixture of stereoisomers thereof, or a salt thereof, or a composition thereof, or a delivery system or a sustained release system thereof, for use in the preparation of an opacifying agent.

In another aspect of the present disclosure, there is provided a use of a cyclic peptide represented by the above formula (I), or a stereoisomer thereof, or a mixture of stereoisomers thereof, or a salt thereof, or a composition thereof, or a delivery system or a sustained release system thereof, in the preparation of a cosmetic.

In this disclosure, the term "skin" is understood to be the layers that make up it, from the uppermost or stratum corneum to the lowermost or subcutaneous tissue, both endpoints being included. These layers are composed of different types of cells, such as keratinocytes, fibroblasts, melanocytes, and/or adipocytes, among others. In this disclosure, the term "skin" includes the scalp.

The term "care of the skin" refers to the maintenance and care of the skin, improving the condition of the skin, and making the skin delicate, smooth, tender and healthy.

The present disclosure has the following advantages and effects:

1. The cyclic peptide disclosed by the disclosure can inhibit elastase activity, promote collagen production, increase skin elasticity, improve skin firmness, promote regeneration or healing of skin or mucous membrane, inhibit hyaluronidase activity, repair skin barrier, inhibit tyrosinase activity, inhibit melanin production, lighten skin color, fade color spots, eliminate uneven skin color, and has multiple effects of resisting aging, repairing, moisturizing, relieving, whitening and the like.

2. The cyclic peptide of the present disclosure is obtained by performing head-to-tail cyclization by condensation reaction of an N-terminal free amino group and a C-terminal free carboxyl group of the linear peptide GHKK, but the cyclic peptide of the present disclosure achieves unexpected technical effects compared to the linear peptide GHKK.

Drawings

In order to more clearly illustrate the technical solutions of the present disclosure, the drawings that are needed in the description of the present disclosure will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present disclosure, and other drawings may be obtained according to these drawings without inventive effort to a person of ordinary skill in the art.

FIG. 1 is a mass spectrum of cyclic peptide A Cyclo- [ Gly-His-Lys-Lys ].

FIG. 2 is a graph showing the effect of the test sample on the collagen I content.

FIG. 3 is a graph showing the effect of the test sample on the content of collagen III.

Detailed Description

In order that the manner in which the above recited objects, features and advantages of the present disclosure are obtained will become more readily apparent, a more particular description of the disclosure will be rendered by reference to the appended drawings and examples. It will be apparent that the described embodiments are some, but not all, of the embodiments of the present disclosure. Based on the embodiments in this disclosure, all other embodiments that may be obtained by one of ordinary skill in the art without inventive effort are within the scope of the claims appended hereto.

In the present disclosure, the abbreviations used for amino acids follow the rules specified by the IUPAC-IUB Biochemical nomenclature Commission (IUPAC-IUB Commission of Biochemical Nomenclature) in the European journal of biochemistry (Eur. J. Biochem.1984, 138:9-37).

Unless otherwise indicated, all reagents and materials used in the present disclosure are commercially available. The following are abbreviations for part of the reagents and materials:

2-CTC Resin: a starting resin (2-chlorotrityl chloride resin) for polypeptide synthesis; DMF: n, N-dimethylformamide; DCM: dichloromethane; DIPEA: diisopropylethylamine; meOH: methanol; piperidine: piperidine; HOBt: 1-hydroxybenzotriazole; DIC: diisopropylcarbodiimide; TFA: trifluoroacetic acid; HBTU: benzotriazol-N, N' -tetramethylurea hexafluorophosphate; TIS: triisopropylsilane; gly: glycine; his: histidine; lys: lysine; fmoc: 9-fluorenylmethoxycarbonyl; trt: a trityl group; boc: and tert-butoxycarbonyl group.

EXAMPLE 1 preparation of Cyclo- [ Gly-His-Lys-Lys ]

1.1 Swelling of resin

10G of 2-CTC Resin was weighed into a solid phase synthesis reaction column, swelled with DCM, the Resin washed, and the solvent was removed.

1.2 Feeding reaction

11G of Fmoc-Lys (Boc) -OH and 11.2mL of DIPEA were weighed and added to the swollen resin to react for 3h, the reaction solution was removed, the resin was washed, and the solvent was removed. The capping treatments with DCM, meOH and DIPEA were continued for 30min, the resin was washed and the solvent was pumped away. Fmoc-Lys (Boc) -2-CTC Resin was obtained.

Fmoc-Lys (Boc) -2-CTC Resin was Fmoc-removed twice with 20% piperidine/DMF for 10min each time, sampled K and developed dark blue. The resin was washed 7 times with DMF and the solvent was removed.

11G of Fmoc-Lys (Boc) -OH,3.5g of HOBt were weighed into a drying flask, dissolved in DMF and sealed in a-18℃refrigerator for 30min. 4.3mL DIC was added to activate for 7min to avoid water vapor. And adding the activated amino acid into the deprotected resin to react for 3 hours, and pumping out the reaction solution. K detection resin is colorless and transparent, which indicates that the reaction is complete.

The N-terminal Fmoc group was deprotected and 14.5g of activated Fmoc-His (Trt) -OH was coupled to the peptidyl resin using DMF as solvent in the presence of 3.5g HOBt and 4.3mL DIC for 4h. These resins were then washed and the deprotection treatment of the Fmoc group was repeated to couple the next amino acid. The coupling of 7g Fmoc-Gly-OH was continued using DMF as solvent in the presence of 3.5g HOBt and 4.3mL DIC. After the reaction was completed, the resin was washed and the solvent was removed.

The N-terminal Fmoc group of the peptidyl resin was deprotected and Fmoc was removed twice with 20% piperidine/DMF for 10min each time, sampling K and developing dark blue. The resin was washed 6 times with DMF and the solvent was removed. After shrink drying 5g of H-Gly-His (Trt) -Lys (Boc) -Lys (Boc) -2-CTC Resin was obtained.

1.3 Resin removal

1ML of TFA and 99mL of DCM were measured and mixed and stirred uniformly to obtain a lysate.

5G of H-Gly-His (Trt) -Lys (Boc) -Lys (Boc) -2-CTC Resin was weighed, added to a round bottom flask, the above lysate was added, and the reaction was stirred for 0.5H. Suction filtration, collecting filtrate, spin drying, 3.2g H-Gly-His (Trt) -Lys (Boc) -Lys (Boc) -OH.

1.4 Cyclization

3.2G of H-Gly-His (Trt) -Lys (Boc) -Lys (Boc) -OH was weighed out in 200mL of DCM, then 1.6g of HBTU and 0.6g of DIPEA were added and reacted for 12H. Monitored by HPLC until the reaction was complete. Pure water was added to the reaction mixture to extract 3 times, and the aqueous phase was spin-dried to obtain 5g of oily Cyclo- [ Gly-His (Trt) -Lys (Boc) -Lys (Boc) ].

1.5 Cleavage (deprotection group)

23ML of TFA, 0.62mL of TIS and 0.62mL of water were weighed and mixed well, and the above-mentioned Cyclo- [ Gly-His (Trt) -Lys (Boc) -Lys (Boc) ] was added thereto and stirred well for 2h. The solid was then filtered off and washed 4 times with isopropyl ether to give 1g of crude cyclic- [ Gly-His-Lys-Lys ] cyclopeptide.

1.6 Purification

1G of crude cyclic- [ Gly-His-Lys-Lys ] cyclopeptide is weighed and dissolved in pure water, and the solution is filtered by a microporous filter membrane with the pore diameter of 0.45 mu m to obtain a clear and transparent solution, and the clear and transparent solution is purified by reversed phase HPLC, wherein the purification gradient is shown in the following table:

time (min)	Flow rate (mL/min)	A% (acetonitrile)	B% (pure water)
				0	40	0	100
8	40	0	100
				18	40	5	95
20	40	20	80
				25	40	20	80
27	40	0	100
				35	40	0	100

And (3) purifying the filtered sample, collecting fractions, concentrating and freeze-drying to obtain the cyclop- [ Gly-His-Lys-Lys ] with the purity of 95.22%, and marking the cyclopeptide A.

The molecular weight was measured by ESI-MS, and the result of the measurement of the cyclopeptide A is shown in FIG. 1, and the result shows that the mass-to-charge ratio (M/z) of the [ M+H ] ⁺ ion peak is 451.84, and the molecular weight measured by mass spectrometry is 450.84.

The linear peptide H-Gly-His-Lys-Lys-OH can be obtained by a similar preparation method.

Example 2 collagen I content test

2.1 Reagents and materials

Fetal bovine serum, DMEM medium, phosphate Buffered Saline (PBS), trypsin, RIPA lysate, collagen I ELISA kit, BCA protein kit.

2.2 Instruments

An enzyme-labeled instrument, a CO ₂ incubator and an ultra-clean workbench.

2.3 Cell lines

Human Skin Fibroblasts (HSF).

2.4 Sample to be tested

Sample group: cyclic peptide a, linear peptide (GHKK), test concentrations of 25ppm;

blank control group: PBS;

UV group: UV radiation, PBS was added.

2.5 Experimental methods

Taking HSF fibroblasts in an exponential growth phase state, adding 0.25% trypsin digestion solution, digesting to enable adherent cells to fall off, and counting (1-4) multiplied by 10 ⁵/mL to prepare a cell suspension.

And inoculating the diluted cell suspension on a 12-hole plate for culturing for 24 hours, and establishing a UV photoaging model when the cells grow to about 80%. The blank group was added with 200 μ LPBS, supplemented with medium to 800 μl, and no UV irradiation was performed; after the UV group and the sample group are repeatedly washed to be colorless by adding a proper amount of PBS, 200 mu L of PBS is added, and the mixture is irradiated under a UV lamp of 80mJ/cm ², and the distance between a lamp source and a culture flask is 15cm. After irradiation, PBS was discarded, the UV group was added to the PBS solution and medium to 800. Mu.L, and the sample group was added to the medium and relevant concentration samples to 800. Mu.L. The blank, UV, sample groups were incubated in a 5% CO ₂ incubator at 37℃for a further 48h.

After the culture, the cells were collected, centrifuged to discard the supernatant, the RIPA lysate was added, homogenized 3 times (30 s/time, 3min interval) with a vortex meter, centrifuged 12000rpm for 10min, and the supernatant was aspirated and tested according to the collagen I ELISA protocol.

2.6 Experimental results

The type I collagen is the most abundant collagen in a human body, is in a thick and tightly arranged bundle-shaped structure, has strong tensile resistance, provides stronger supporting structure and supporting force for skin, and endows the skin with elasticity and toughness, so that the improvement of the content of the type I collagen has important significance for preventing aging and increasing skin elasticity and compactness. The experiment adopts a test sample to treat cells after ultraviolet radiation, and detects the content of type I collagen in corresponding cells so as to determine whether the cyclic peptide disclosed by the invention can promote the generation of type I collagen.

The effect of the test sample on the collagen I content is shown in fig. 2. The results showed that the collagen I content of the UV group was significantly reduced compared to the blank group, indicating that modeling was successful (# # indicated P <0.01, with significant statistical differences); compared with the UV group, the cyclopeptide A can obviously improve the content of collagen I and promote the generation of type I collagen (P <0.01 is shown by the x, and obvious statistical difference exists); the linear peptide can not improve the content of the collagen I, which shows that the cyclic peptide A obtained by the head-to-tail cyclization of the present disclosure has a novel effect relative to the linear peptide before the cyclization, and can remarkably promote the generation of the type I collagen, thus obtaining unexpected technical effects.

From the results, the cyclic peptide disclosed by the invention can increase the content of collagen in cells, promote the generation of collagen, thereby increasing the skin elasticity, improving the skin firmness and delaying skin aging.

EXAMPLE 3 collagen III content test

3.1 Reagents and materials

Fetal bovine serum, DMEM medium, phosphate Buffer (PBS), trypsin, RIPA lysate, collagen III ELISA kit, BCA protein kit.

3.2 Instruments

An enzyme-labeled instrument, a CO ₂ incubator and an ultra-clean workbench.

3.3 Cell lines

Human Skin Fibroblasts (HSF).

3.4 Sample to be tested

Sample group: cyclic peptide a, linear peptide (GHKK), test concentrations were 25ppm, 50ppm;

blank control group: PBS;

UV group: UV radiation, PBS was added.

3.5 Experimental methods

And inoculating the diluted cell suspension on a 12-hole plate for culturing for 24 hours, and establishing a UV photoaging model when the cells grow to about 80%. The blank group was added with 200 μ LPBS, supplemented with medium to 800 μl, and no UV irradiation was performed; after the UV group and the sample group are repeatedly washed to be colorless by adding a proper amount of PBS, 200 mu L of PBS is added, and the mixture is irradiated under a UV lamp of 80mJ/cm ², and the distance between a lamp source and a culture flask is 15cm. After irradiation, PBS was discarded, the UV group was added to the PBS solution and medium to 800. Mu.L, and the sample group was added to the medium and samples of different concentrations to 800. Mu.L. The blank, UV, sample groups were incubated in a 5% CO ₂ incubator at 37℃for a further 48h.

After the culture, the cells were collected, centrifuged to discard the supernatant, the RIPA lysate was added, homogenized 3 times (30 s/time, 3min interval) with a vortex meter, centrifuged 12000rpm for 10min, and the supernatant was aspirated and tested according to the collagen III ELISA protocol.

3.6 Experimental results

The III type collagen belongs to collagen forming fibers, is mainly present at the junction of the dermis layer and the epidermis layer, provides elasticity and stress resistance for skin, can repair damaged I type collagen, stimulates regeneration of I type collagen, has good effect of promoting repair and healing, and therefore, the improvement of III type collagen content has important significance for tightening skin and repairing damaged skin. The experiment adopts a test sample to treat cells after ultraviolet radiation, and detects the content of type III collagen in corresponding cells so as to determine whether the cyclic peptide disclosed by the invention can promote the generation of type III collagen.

The effect of the test sample on the collagen III content is shown in fig. 3. The results showed that the collagen III content of the UV group was significantly reduced compared to the blank group, indicating that modeling was successful (# # indicated P <0.01, with significant statistical differences); compared with the UV group, the cyclic peptide a can significantly increase the content of collagen III, promote the generation of type III collagen (P <0.05, with statistical difference), whereas the linear peptide cannot increase the content of collagen III, indicating that the cyclic peptide a of the present disclosure achieves unexpected technical effects relative to the linear peptide before cyclization.

Therefore, the cyclic peptide disclosed by the invention can increase the content of collagen in cells, promote the generation of collagen, further increase the skin elasticity, improve the skin firmness, repair the skin or mucous membrane, promote the regeneration or healing of the skin or mucous membrane, and have the effects of resisting aging and repairing.

Example 4 elastase inhibition assay

4.1 Reagents and materials

PBS, elastase solution, AAAPAN (N-succinyl-alanine-p-nitroaniline) solution.

4.2 Instruments

An enzyme-labeled instrument and an electronic balance.

4.3 Samples to be tested and groupings

4.3.1 Sample to be tested

Cyclic peptide A, linear peptide (GHKK) were tested at 10ppm.

4.3.2 Grouping

Sample group: sample to be tested, PBS, elastase, AAAPAN;

sample zeroing group: sample to be measured, PBS, AAAPAN;

Blank control group: PBS, elastase, AAAPAN;

blank zeroing group: PBS, AAAPAN.

4.4 Experimental methods

Taking a 96-well plate, adding 85 mu L of PBS, 15 mu L of a sample to be tested and 25 mu L of elastase solution (2 mg/mL) into a sample group; adding 110 mu L of PBS and 15 mu L of sample to be detected into the sample zeroing group; 100. Mu.L of PBS and 25. Mu.L of elastase solution (2 mg/mL) were added to the blank; blank zeroed groups were added with 125 μl PBS. After incubation at 25℃for 15min, a further 25. Mu. LAAAPAN solution (1.015 mmol/L) was added to each well and incubated at 25℃for 15min. OD ₄₁₀ was measured at 410 nm.

Wherein: a ₁ is the OD ₄₁₀ value for the sample zeroed group, a ₂ is the OD ₄₁₀ value for the sample group, a ₃ is the OD ₄₁₀ value for the blank zeroed group, and a ₄ is the OD ₄₁₀ value for the blank control group.

4.5 Experimental results

The elastase has the capability of degrading various proteins such as collagen, elastin and the like, and the elastin in skin is closely related to skin aging, so that the activity of the elastase is inhibited, the degradation of the elastin is reduced, and the elastase has important significance for recovering skin elasticity and delaying skin aging. AAAPAN is a substrate for elastase, which is decomposed under the catalysis of elastase, and the decomposition product absorbs visible light with a wavelength of 410 nm. The present experiment uses a test sample to treat elastase and detects AAAPAN the amount of reaction to determine whether the cyclic peptides of the present disclosure inhibit elastase activity. The results of the inhibition of elastase activity by the test samples are shown in Table 1.

Table 1 test samples for inhibition of elastase activity (n=3)

Concentration of	Cyclic peptide A	Linear peptides
			10ppm	30.4％	16.1％

The results show that at a low concentration of 10ppm, the inhibition of elastase activity by cyclopeptide a of the present disclosure is 30.4%, whereas the inhibition of elastase activity by the linear peptide is only 16.1%. Under the same concentration, the elastase inhibition rate of the cyclopeptide A is obviously higher than that of the linear peptide, which indicates that the cyclopeptide A obtained by the head-to-tail cyclization of the cyclopeptide A has better technical effect compared with the linear peptide before the cyclization, and the elastase activity inhibition capability of the cyclopeptide A is obviously improved.

From the results, the cyclic peptide disclosed by the invention has excellent capability of inhibiting elastase activity, and can reduce elastin decomposition, increase skin elasticity and/or improve skin firmness, improve skin problems such as skin relaxation and wrinkles and realize the effects of resisting aging, tightening and removing wrinkles by inhibiting elastase activity.

EXAMPLE 5 hyaluronidase inhibition assay

5.1 Reagents and materials

Sodium acetate buffer (ph=5.6), hyaluronidase, calcium chloride, sodium hyaluronate, acetylacetone, absolute ethanol, sodium carbonate, P-DAB (P-dimethylaminobenzaldehyde (0.8 g) and concentrated hydrochloric acid (15 mL) and an equal amount of glacial acetic acid were homogeneously mixed to obtain the final product.

5.2 Instruments

An enzyme-labeled instrument and an electronic balance.

5.3 Samples to be tested and groupings

5.3.1 Sample to be tested

Cyclic peptide A, linear peptide (GHKK) were tested at 500ppm.

5.3.2 Grouping

Sample group: a sample to be tested, hyaluronidase and sodium hyaluronate;

Sample zeroing group: sample to be measured, sodium acetate buffer;

Blank control group: distilled water, hyaluronidase, sodium hyaluronate;

Blank zeroing group: distilled water and sodium acetate buffer.

5.4 Experimental methods

Hyaluronidase and sodium hyaluronate are dissolved in sodium acetate buffer.

Taking a 96-well plate, adding 25 mu L of a sample to be detected and 25 mu L of hyaluronidase (1000U/mL) into a sample group; adding 25 mu L of sample to be detected and 25 mu L of sodium acetate buffer solution into the sample zeroing group; 25. Mu.L distilled water and 25. Mu.L hyaluronidase (1000U/mL) were added to the blank; the blank zeroing group was added with 25. Mu.L distilled water and 25. Mu.L sodium acetate buffer. After shaking for 20min at 37℃in a constant temperature gas bath, 5. Mu.L of calcium chloride solution (2.5 mol/L) was added to each well, and the mixture was shaken for 20min at 37℃in a constant temperature gas bath. 25 mu L of sodium hyaluronate (1 mg/mL) is added into the sample group and the blank control group, 25 mu L of sodium acetate buffer solution is added into the sample zeroing group and the blank zeroing group, and the mixture is placed at the constant temperature of 37 ℃ for shaking for 40min, and then is placed at the room temperature for 10min. Each well was further charged with 25. Mu.L of distilled water, 5. Mu.L of sodium hydroxide solution (5 mol/L), and 25. Mu.L of acetylacetone solution, and the mixture was placed in an oven at 90℃for 15min, further ice-bath for 10min, and finally at room temperature for 10min. 50. Mu.L of DAB was added to each well, followed by 100. Mu.L of absolute ethanol, and the mixture was left at room temperature for 30min and at 570nm to determine OD ₅₇₀.

Wherein: a ₁ is the OD ₅₇₀ value for the sample zeroed group, a ₂ is the OD ₅₇₀ value for the sample group, a ₃ is the OD ₅₇₀ value for the blank zeroed group, and a ₄ is the OD ₅₇₀ value for the blank control group.

5.5 Experimental results

Hyaluronidase can decompose hyaluronic acid in vivo to become low molecular weight acidic stimulus, thereby inducing histamine release and inducing body to produce sensitive symptoms. In addition, the reduction of hyaluronic acid can disrupt the barrier function of the skin, resulting in loss of moisture from the interior of the skin. Therefore, the effect of relieving, moisturizing and repairing the skin barrier can be achieved by inhibiting the activity of hyaluronidase. The present experiment employs a test sample to treat hyaluronidase, and the reaction amount of sodium hyaluronate is detected to determine whether the cyclic peptide of the present disclosure can inhibit the activity of hyaluronidase. The results of the inhibition of hyaluronidase activity by the test samples are shown in Table 2.

Table 2 test samples for inhibition of hyaluronidase activity (n=3)

Concentration of	Cyclic peptide A	Linear peptides
			500ppm	74.4％	42.5％

The results show that at 500ppm concentration, the cyclic peptide a of the present disclosure has an inhibition of hyaluronidase activity as high as 74.4%, whereas the linear peptide has an inhibition of hyaluronidase activity of 42.5%. Under the same concentration, the hyaluronidase inhibition rate of the cyclopeptide A is obviously higher than that of the linear peptide, which indicates that the cyclopeptide A obtained by the head-to-tail cyclization of the cyclopeptide A has better technical effect compared with the linear peptide before the cyclization, and the hyaluronidase activity inhibition capability of the cyclopeptide A is obviously improved.

From these results, the cyclic peptide of the present disclosure can inhibit the activity of hyaluronidase and exert the effects of soothing, moisturizing and repairing skin barrier.

EXAMPLE 6 Mushroom tyrosinase inhibition assay

6.1 Reagents and materials

PBS, mushroom tyrosinase, L-DOPA.

6.2 Instruments

Thermostatic water bath pot and enzyme label instrument.

6.3 Samples to be tested and groupings

6.3.1 Sample to be tested

Cyclic peptide A and linear peptide (GHKK) were tested at 200ppm and 500ppm.

6.3.2 Grouping

Sample group: sample to be tested, tyrosinase, PBS and L-DOPA;

sample zeroing group: sample to be measured, PBS, L-DOPA;

blank control group: PBS, tyrosinase, L-DOPA;

Blank zeroing group: PBS, L-DOPA.

6.4 Experimental methods

Taking a 96-well plate, adding 50 mu L of a sample to be detected and 50 mu L of tyrosinase (the final concentration is 25U/mL) into a sample group; adding 50 mu L of sample to be detected and 50 mu L of PBS into the sample zeroing group; the blank group was added with 50. Mu. LPBS, 50. Mu.L tyrosinase (final concentration 25U/mL); blank zeroed groups were added with 100 μl PBS. Incubation was carried out at 37℃for 5min. mu.L of PBS and 50 mu L L-DOPA (final concentration 0.5 mmol/L) were added to each well and incubated at 37℃for 10min. OD ₄₇₅ was measured at 475nm and tyrosinase inhibition was calculated.

Wherein: a ₁ is the OD ₄₇₅ value for the sample zeroed group, a ₂ is the OD ₄₇₅ value for the sample group, a ₃ is the OD ₄₇₅ value for the blank zeroed group, and a ₄ is the OD ₄₇₅ value for the blank control group.

6.5 Experimental results

The results of the inhibition of tyrosinase activity by the test samples are shown in Table 3.

Table 3 test samples for inhibition of tyrosinase activity (n=3)

The results show that the linear peptide has no influence on the activity of tyrosinase, while the cyclic peptide A can obviously inhibit the activity of tyrosinase at the same concentration. The inhibition rate of the cyclopeptide A on tyrosinase activity at the concentration of 200ppm is 11.7%, and the inhibition rate at the concentration of 500ppm is further improved to 16.0%. From this, it was demonstrated that the cyclic peptide a of the present disclosure produces a novel effect with respect to the linear peptide before cyclization, and can inhibit tyrosinase activity, thereby achieving unexpected technical effects.

Therefore, the cyclic peptide disclosed by the invention can inhibit the activity of tyrosinase and reduce the generation of melanin, can be used for brightening skin, fading and removing color spots or eliminating uneven skin color, realizes the effect of whitening and removing spots, can be used in whitening and removing spots products, and can also be used for preparing opacifiers.

Example 7A cyclopeptide A containing essence

The preparation method comprises the following steps: adding the materials of the phase A into a stirring pot according to the dosage of the formula, stirring and heating to 80-85 ℃; uniformly mixing the materials in the phase B until powder particles are absent, adding the materials into a stirring pot, and continuously stirring for 10-15min; cooling to 60-65deg.C, and adding C phase material; cooling to 35-40deg.C, adding D phase and E phase materials, and stirring for 10-15 min.

EXAMPLE 8 cream containing cyclopeptide A

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The preparation method comprises the following steps: heating the D phase material to 55-60 ℃ in a proper container according to the dosage of the formula, and completely dissolving for later use; adding the phase A into a stirring pot, stirring and heating to 80-85 ℃; adding the materials in the phase B into an oil phase pot, stirring and heating to 75-80 ℃, and completely dissolving and transparency; adding phase B into phase A, vacuum-homogenizing for 5min, stirring, and maintaining the temperature for 20min; cooling to 60-65deg.C, adding C phase and pre-dissolved D phase material, homogenizing for 2min; cooling to 35-40deg.C, adding E phase material, and stirring for 10-15 min.

In this disclosure, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or terminal that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or terminal. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or terminal device that comprises the element.

Although specific embodiments of the disclosure have been described for illustrative purposes, various modifications or improvements can be made by those skilled in the art without departing from the spirit and scope of the disclosure. Such variations and modifications are intended to fall within the scope of the claims appended hereto.

Claims

1. A cyclic peptide or a salt thereof, characterized in that the cyclic peptide has a structure represented by formula (I):

Cyclo-[Gly-His-Lys-Lys](I)。

2. the cyclic peptide of the formula (I) or a salt thereof according to claim 1,

The salts include metal salts of cyclic peptides of formula (I), the metal comprising: lithium, sodium, potassium, calcium, magnesium, manganese, copper, zinc or aluminum;

Or the salt comprises a salt formed by cyclic peptide shown in the formula (I) and an organic base, wherein the organic base comprises: ethylamine, diethylamine, ethylenediamine, ethanolamine, diethanolamine, arginine, lysine, histidine or piperazine;

Or the salt comprises a salt formed by cyclic peptide shown in the formula (I) and inorganic acid or organic acid, wherein the organic acid comprises: acetic acid, citric acid, lactic acid, malonic acid, maleic acid, tartaric acid, fumaric acid, benzoic acid, aspartic acid, glutamic acid, succinic acid, oleic acid, trifluoroacetic acid, oxalic acid, pamoic acid or gluconic acid; the inorganic acid includes: hydrochloric acid, sulfuric acid, boric acid or carbonic acid.

3. A composition comprising an effective amount of a cyclic peptide of formula (I) or a salt thereof according to claim 1 or 2, together with at least one excipient and optionally an adjuvant.

4. A composition according to claim 3, wherein the adjuvant is selected from the group consisting of: analgesic, agent that inhibits PAR-2 activity, collagen synthesis stimulator, agent that regulates PGC-1 alpha synthesis, agent that regulates PPARgamma activity, agent that increases or decreases triglyceride content of adipocytes, agent that stimulates or delays adipocyte differentiation, lipolytic agent or agent that stimulates lipolysis, lipolytic agent, adipogenic agent, inhibitor of acetylcholine receptor aggregation, agent that inhibits muscle contraction, anticholinergic agent, elastase inhibitor, matrix metalloproteinase inhibitor, melanin synthesis stimulator or inhibitor, whitening agent or decolorizing agent, Pigmentation-promoting agents, self-tanning agents, anti-ageing agents, NO-synthase inhibitors, 5 alpha-reductase inhibitors, inhibitors of lysyl hydroxylase and/or prolyl hydroxylase, antioxidants, free radical scavengers and/or agents against atmospheric pollution, active carbonyl scavengers, anti-glycation agents, antihistamines, antiviral agents, antiparasitic agents, emulsifiers, emollients, organic solvents, liquid propellants, moisture-retaining substances, alpha hydroxy acids, beta hydroxy acids, moisturizers, epidermohydrolases, vitamins, amino acids, proteins, pigments, dyes, biopolymers, gelling polymers, thickeners, surfactants, softeners, Adhesives, preservatives, anti-wrinkle agents, agents capable of reducing or treating the lower pouch, keratolytic agents, antimicrobial agents, agents that stimulate the synthesis of dermal or epidermal macromolecules and/or that inhibit or prevent their degradation, agents that stimulate elastin synthesis, agents that stimulate decorin synthesis, agents that stimulate laminin synthesis, agents that stimulate defensin synthesis, agents that stimulate chaperonin synthesis, agents that stimulate cAMP synthesis, agents that stimulate hyaluronic acid synthesis, agents that stimulate fibronectin synthesis, agents that stimulate deacetylase synthesis, agents that stimulate the synthesis of lipids and stratum corneum components, ceramides, fatty acids, agents that inhibit collagen degradation, Agents that inhibit elastin degradation, agents that inhibit serine protease, agents that stimulate fibroblast proliferation, agents that stimulate keratinocyte proliferation, agents that stimulate adipocyte proliferation, agents that stimulate melanocyte proliferation, agents that stimulate keratinocyte differentiation, agents that inhibit acetylcholinesterase, skin relaxants, agents that stimulate glycosaminoglycan synthesis, anti-hyperkeratosis agents, acne solubilizers, anti-psoriasis agents, anti-rash agents, DNA repair agents, DNA protectants, stabilizers, antipruritic agents, agents for treating and/or caring for sensitive skin, solidifying agents, tightening agents, restructuring agents, anti-stretch marks agents, agents that regulate sebum production, cosmetic agents that are useful in the treatment and/or care of sensitive skin, Antiperspirant, healing-stimulating agent, healing-assisting agent, re-epithelialization-stimulating agent, re-epithelialization-assisting agent, cytokine, sedative, anti-inflammatory agent, anesthetic, agent acting on capillary circulation and/or microcirculation, angiogenesis-stimulating agent, vascular permeability-inhibiting agent, venous tone agent, cell metabolism-acting agent, agent for improving dermal-epidermal junction, hair growth-inducing agent, hair growth-inhibiting or delaying agent, perfume, chelating agent, plant extract, essential oil, marine extract, agent derived from biofermentation process, inorganic salt, cell extract, sunscreen agent, and organic or inorganic photoprotection agent effective against a and/or B ultraviolet rays or a mixture thereof.

5. A delivery system or sustained release system comprising an effective amount of a cyclic peptide of formula (I) or a salt thereof according to claim 1 or 2, or a composition according to claim 3 or 4;

The delivery system or sustained release system comprises: liposomes, oleosomes, ethosomes, millimeter capsules, microcapsules, nanocapsules, nanostructured lipid carriers, sponges, clathrates, lipid vesicles, micelles, millimeter spheres, microspheres, nanospheres, lipid spheres, microemulsions, nanoemulsions, millimeter particles, microparticles or nanoparticles.

6. A cosmetic comprising an effective amount of a cyclic peptide represented by formula (I) or a salt thereof according to claim 1 or 2, or a composition according to claim 3 or 4, or a delivery system or a sustained-release system according to claim 5.

7. The cosmetic product according to claim 6, wherein the formulation of the cosmetic product comprises a cream, an emulsion, an aqueous solution, an oil, a gel, a powder, a tablet, a mud, a patch, a film, an aerosol, a spray, a lyophilized preparation or a nano-preparation.

8. Use of a cyclic peptide of formula (I) or a salt thereof according to claim 1 or 2, or a composition according to claim 3 or 4, or a delivery system or a slow release system according to claim 5, for the preparation of a composition for caring for or treating skin or mucous membranes.

9. Use of a cyclic peptide of formula (I) or a salt thereof according to claim 1 or 2, or a composition according to claim 3 or 4, or a delivery system or a slow release system according to claim 5, for the preparation of a composition for anti-ageing, repairing, moisturizing or soothing.

10. Use of a cyclic peptide of formula (I) or a salt thereof according to claim 1 or 2, or a composition according to claim 3 or 4, or a delivery system or a slow release system according to claim 5, for the preparation of a composition for whitening, lightening skin colour, depigmenting and/or eliminating skin colour non-uniformities.

11. The use of a cyclic peptide of formula (I) as defined in claim 1 or 2 or a salt thereof, or the use of a composition as defined in claim 3 or 4, or a delivery system or a sustained release system as defined in claim 5, for the preparation of a composition for inhibiting elastase activity, or for the preparation of a composition for promoting collagen production, or for the preparation of a composition for increasing skin elasticity and/or improving skin firmness, or for the preparation of a composition for promoting regeneration or healing of skin or mucous membranes, or for the preparation of a composition for repairing skin barriers, or for the preparation of a composition for inhibiting hyaluronidase activity, or for the preparation of a composition for inhibiting tyrosinase activity, or for the preparation of a composition for inhibiting melanin production.

12. Use of a cyclic peptide of formula (I) or a salt thereof according to claim 1 or 2, or a composition according to claim 3 or 4, or a delivery system or a sustained release system according to claim 5, for the preparation of an opacifier.

13. Use of a cyclic peptide of formula (I) or a salt thereof according to claim 1 or 2, or a composition according to claim 3 or 4, or a delivery system or a sustained release system according to claim 5, for the preparation of a cosmetic.