Which are the peptides used in cosmetics?

Introduction

Anti-wrinkle, improvement of elasticity, reduction of expression lines… Peptides in cosmetics are usually associated with products that reduce the signs of aging. However, its use in cosmetics goes much further thanks to its properties and its ability to penetrate the skin.

What are the cosmetic peptides?

Peptides are molecules formed by joining amino acids through peptide bonds, just like proteins. But these are usually longer chains than peptides. Human skin has two main peptides that play a fundamental role in maintaining its quality:

Collagen

It is one of the most abundant proteins in the human body. Its function in the skin is to maintain the level of hydration and, together with elastin, maintain its elasticity and firmness. Collagen is not only found in the skin, there are various types of collagen in bones, cartilage, or tendons in which collagen molecules form chains to increase their resistance.

Elastin

Elastin is a protein that provides elasticity by intertwining its molecules. Elastin also provides a great capacity for expansion in the tissues in which it is found, predominantly skin and ligaments. Elastin and collagen levels decrease with age. Around the age of 25, collagen production is reduced, this reduction being much more pronounced when entering menopause, in the case of women.

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For this reason, the cosmetic industry has developed different peptides that help preserve the quality of the skin when the levels of endogenous proteins decrease.

What properties do cosmetic peptides have?

Synthetic peptides developed by the cosmetic industry must penetrate the skin to perform their function, so they must have a series of specific characteristics [1]:

• • They must be small molecules, with a molecular weight of no more than 500 Daltons.
  • Its octanol/water partition coefficient should be moderate: between 1 and 3
  • The melting point must be less than 200ºC
  • They must be soluble in water (>1 mg/mL^-1)
  • Possess few or no polar centers

How cosmetic peptides work

Anti-aging

The peptides used in anti-aging cosmetic formulations are the most used, being a market that worldwide reaches sales worth millions of US dollars.

Among the anti-aging peptides, we find Matrixyl ®, which stimulates the production of proteins in the extracellular matrix, especially collagen, but also elastin or fibronectin. In the opposite way, peptides from soy or rice (Colhibin PF®) act on collagen levels reducing its degradation by inhibiting proteinases [1].

On the other hand, there are anti-aging peptides, such as Argireline® or Leuphasy®, which work in a similar way to botox. That is, by reducing the release of acetylcholine at the neuromuscular junction and, therefore, paralyzing muscle contraction and thus reducing the appearance of wrinkles [1].

Melanin modulation

The cosmetic industry has not only developed anti-aging peptides. For the development of products that protect the skin from the effects of the sun, peptide analogs of the melanocyte-stimulating hormone have been developed that stimulate melanogenesis and act as photoprotection [2].

Image by Igor Link from Pixabay

Delivery peptides

Some peptides are designed to increase skin penetration of other components present in the formulation. This is the case of the GHK peptide, which facilitates the transport of bioactive molecules through the skin, such as vitamin C or copper. The latter is necessary for the proper functioning of some enzymatic reactions, such as superoxide dismutase involved in collagen production [1,2].

Sensitive skin

Peptides used in formulations for sensitive skin stand out for their ability to interact with skin cells by multiple mechanisms, high potency at low doses, and the ability to penetrate the stratum corneum [3]. Among them, the most widely used are acetyl dipeptide-1 cetyl ester, palmitoyl tripeptide-8, palmitoyl tripeptide-5, acetyl hexapeptide-49, and acetyl tetrapeptide-15 [3]:

• • Acetyl dipeptide-1 cetyl ester reduces inflammation and itching by reducing the release of CGRP
  • Palmitoyl tripeptide-8 reduces skin redness by inhibiting IL-8 production in keratinocytes
  • Palmitoyl tripeptide-5 is a fragment of thrombospondin I that reduces the expression of metalloproteases and the synthesis of proinflammatory cytokines
  • Acetyl hexapeptide-49 regulates the activity of PAR-2, reducing the inflammatory response led by interleukins 6 and 8, the activation of the TRPV1 channel and, consequently, the release of CGRP
  • Acetyl tripeptide-15 is a derivative of endomorphine 2, a µ-opioid receptor agonist that reduces skin hyperreactivity by increasing the activation threshold of these receptors

In conclusion, peptides represent a versatile element for the formulation of different cosmetic solutions beyond anti-aging products.

References

1. Gorouhi, F., & Maibach, H. I. (2009). Role of topical peptides in preventing or treating aged skin. International journal of cosmetic science, 31(5), 327–345. https://doi.org/10.1111/j.1468-2494.2009.00490.x
2. Pai, V. V., Bhandari, P., & Shukla, P. (2017). Topical peptides as cosmeceuticals. Indian journal of dermatology, venereology and leprology, 83(1), 9–18. https://doi.org/10.4103/0378-6323.186500
3. Resende, D., Ferreira, M. S., Sousa-Lobo, J. M., Sousa, E., & Almeida, I. F. (2021). Usage of Synthetic Peptides in Cosmetics for Sensitive Skin. Pharmaceuticals (Basel, Switzerland), 14(8), 702. https://doi.org/10.3390/ph14080702

Cover image by WikiMediaImages from Pixabay