SKIN CARE
Review of vitamin A in skin care
Dr Cuross Bakhtiar – Harley Street Cosmetic, UK ABSTRACT
Vitamin A is the first vitamin approved by the FDA as an anti-wrinkle agent that changes appearance of the skin surface and has anti-ageing effects. Vitamin A is in a group of fat-soluble substances and belongs to the category of retinoids. Apart from retinol, that group includes structurally related substances with the biological properties of retinol. Since the biological activity of the substances differs, for the purpose of standardisation, it is given in retinol equivalents. Vitamin A and its derivatives are among the most effective substances for slowing the ageing process. Retinoids regulate cell apoptosis, differentiation and proliferation. Anti-wrinkle properties of retinoids promote keratinocytes proliferation, strengthen the protective function of the epidermis, restrain trans epidermal water loss, protect collagen against degradation and inhibit metalloproteinases activity. Retinoid activity is related to high affinity for nuclear receptors: retinoid acid receptors and retinoid X receptors.
According to the IUPAC (International Union of Pure & Applied Chemistry) and IUBMB (International Union of Biochemistry and Molecular Biology), retinoids are compounds containing four isoprene units with a head- to-tail structure.1
Retinol, retinoic aldehyde
and retinoic acid (RA) belong to retinoids with a non-aromatic fragment of β-ionone in their molecule. The term ‘retinoid’ refers to the synthetic and natural analogues of vitamin A. Retinoids are a class of compounds
derived from vitamin A or showing structural and/or functional similarities to vitamin A. According to the latter definition, retinoids are molecules that can bind to and activate the appropriate nuclear receptors and to induce transcription of relevant genes either directly or after metabolic transformation.2 Retinoids are widely applied in cosmetics as a potent dermatological agent used in acne, psoriasis as well as other skin diseases. The retinoid family comprises vitamin A (retinol) and its natural derivatives such
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as retinaldehyde, retinoic acid, and retinyl esters, as well as a large number of synthetic derivatives.3
Retinoids are compounds of both natural, Retinol is a 20-carbon molecule
that consists of a cyclohexenyl ring, a side chain with four double bonds (all in trans configuration), and an alcohol end group, hence the name all-trans-retinol. The oxidation of the alcohol end group in
retinol results in the formation of an aldehyde (all-trans retinaldehyde or retinal), which can be further oxidised to a carboxylic acid (all-trans retinoic acid or tretinoin). Vitamin A cannot be synthesised by the body; hence it needs to be supplied to the body. Naturally, retino is present as retinyl esters and beta-carotene. The retinyl esters are converted to retinol before absorption from the intestine and back to retinyl esters for storage in the liver. The objective of this study is to introduce
and compare different types of retinoid uses in cosmetic and dermatological treatments. Moreover, this paper should address the issue of the cellular activity of retinoids.
biologically active forms of vitamin A (retinol, retinal and retinoic acid) and synthetic analogues of retinol (Figures 1 & 2). Synthetic analogues have a benzene ring instead of cyclohexane (etretinate, acitretin, tazarotene). Based on the molecular structure and properties, retinoids can be divided into three generations: Retinol, retinal and retinoic acid have the same biological features as vitamin A. Retinoids are involved in the process of embryogenesis during development of the nervous system, liver, heart, kidneys, intestine, eyes and limbs. They are used in treatment of the so-called ‘night blindness’ because they are responsible for proper functioning of the organ of sight. They are associated with formation of rhodopsin. They are also used in pharmacotherapy of diseases such as acne and rosacea, psoriasis, cancer, inflammation of hair follicles with bacterial aetiology, pyoderma, lupus erythematosus and ichthyosis. Retinol does not exert a significant
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