α-arbutin, is a glycosylatedhydroquinone, and an anomer of the naturally occurring arbutin. α-Arbutin is used in the cosmetic and pharmaceutical industries for its skin lightening effects, treatment of hyperpigmentation, and as a safer alternative to hydroquinone.
Structurally it is the α-anomer of arbutin (β-arbutin), and like the β-form it is an enzyme inhibitor of human tyrosinase.[1]
Uses
α-Arbutin is used in the cosmetic and pharmaceutical industries for its skin lightening effects, treatment of hyperpigmentation, and as a possibly safer alternative to hydroquinone. It may also possess antioxidant properties, which can protect the skin from free radical damage.[3]
It is used in products aimed at fading solar lentigo, freckles, melasma, and other forms of hyperpigmentation where excess melanin is a concern, providing a more even skin complexion.[4] For this purpose, concentrations of up to 2% α-arbutin are found in face creams and serums and 0.5% in body creams.[1]
α-Arbutin showed a significant reduction in melanin synthesis in cultured human melanoma cells and a three-dimensional human skin model, with melanin synthesis reduced to 40% of the control, indicating its potency as a skin lightening agent without affecting cell viability.[4]
Mechanism of action
α-Arbutin's mechanism of action as a skin lightening agent is primarily through the competitive enzymatic inhibition of tyrosinase, leading to a decrease in melanin production without affecting the mRNAgene expression of tyrosinase. It is more potent an inhibitor of tyrosinase than arbutin.[2]
α-Arbutin directly inhibits the enzymatic activity of tyrosinase, which is essential for melanin synthesis. Tyrosinase catalyzes the first two steps in melanin production: the hydroxylation of tyrosine to l-DOPA and the oxidation of l-DOPA to dopaquinone. By inhibiting tyrosinase, α-arbutin reduces the formation of melanin in melanocytes.[5]
α-Arbutin does not affect the gene expression of tyrosinase mRNA. This means that while α-arbutin inhibits the activity of the tyrosinase enzyme, it does not decrease the enzyme's production at the genetic level.[2][6]
This reduction in melanin leads to lighter skin tones and can help in the treatment of hyperpigmentation disorders. The efficacy of α-arbutin in reducing melanin synthesis was demonstrated in cultured human melanoma cells and a three-dimensional human skin model, where it effectively reduced melanin synthesis.[4]