Review of vitamin A in skin care

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 headto-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.