November 10, 2011

Found in the leaves of pear trees and certain plants such as wheat and bearberry, and in lower quantities in cranberry and blueberry leaves (Dermatol. Ther. 2007;20:308-13), arbutin (C₁₂H₁₆O₇) is a naturally occurring B-D glucopyranoside consisting of a molecule of hydroquinone bound to glucose (in other words, the beta-D-glucopyranoside of hydroquinone). Arbutin has been used traditionally in Japan as a skin-lightening agent. Its depigmenting mechanism is thought to act by reversibly suppressing melanosomal tyrosinase activity rather than inhibiting the expression and production of tyrosinase (J. Pharmacol. Exp. Ther. 1996;276:765-9). It also acts by inhibiting 5,6-dihydroxyindole-2-carboxylic acid (DHICA) polymerase; the hydrolyzation of the glycosidic bond then results in hydroquinone release in a controlled manner (Dermatol. Clin. 2007;25:353-62; Pigment Cell. Res. 2006;19:550-71). Tyrosinase is the rate-limiting enzyme that controls melanin production and is a unique product of melanocytes. Consequently, agents that inhibit tyrosinase activity, which is a major regulatory step in melanogenesis, prevent the synthesis of the pigment melanin and are therefore considered viable candidates as cosmetic skin-whitening ingredients.

Photo credit: Oleg Prikhodko/iStockphoto.com   Arbutin, found in the leaves of the pear tree and in other plants, has been used as a skin-lightening agent in traditional Japanese medicine.

Currently, arbutin is included as an ingredient in several cosmetic products. This column will focus on recent research with arbutin and deoxyarbutin, a synthetic arbutin derivative, created by removing each hydroxyl group, that has shown promising in vitro and in vivo results with a greater inhibition of tyrosinase than its botanical precursor (Exp. Dermatol. 2005;14:601-8). It is important to note that hydroquinone, the standard cosmetic skin-lightening agent, is more potent than arbutin, but it has been associated with cytotoxicity, nephrotoxicity, and genotoxicity (J. Cosmet. Dermatol. 2008;7:189-93) and was banned in Europe in 2000 and is strictly regulated in Asia.

Abutin’s Efficacy Tested

Although arbutin has been reported to be successful for cosmetic and therapeutic purposes, its suitability as an alternative depigmenting agent to hydroquinone has not been firmly established. In a decade-old study, tyrosinase activity diminished in normal human melanocytes treated with arbutin, but an increase of pigmentation was reported (Pigment Cell. Res. 1998;11:12-7). Indeed, Maeda and Fukuda had previously reported that while higher concentrations of arbutin displayed greater efficacy than lower concentrations, a paradoxical hyperpigmentation emerged as a result of postinflammatory hyperpigmentation (J. Pharmacol. Exp. Ther. 1996;276:765-9; Skin Therapy Lett. 2004;9:1-3; Dermatol. Ther. 2007;20:308-13).

In another study in which the inhibitory effect of arbutin and/or aloesin on pigmentation in human skin after UV radiation was examined, the administration of either or both compounds four times a day for 15 days revealed pigmentation suppression of 43.5% by arbutin, 34% by aloesin, and 63.3% by the cotreatment of the skin-lightening agents, compared with the control (Clin. Exp. Dermatol. 2002;27:513-5).

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