Modulation of Melanogenesis by Aloesin: A Competitive Inhibitor of Tyrosinase

Abstract

Aloesin, [2-acetonyl-8-beta-d-glucopyranosyl-7-hydroxy-5-methylchromone], a compound isolated from the Aloe plant, is shown in these studies to modulate melanogenesis via competitive inhibition of tyrosinase. Aloesin inhibits purified tyrosinase enzyme and specifically inhibits melanin production in vitro. Enzyme kinetics studies using normal human melanocyte cell lysates and cell-based melanin production demonstrated that aloesin is a competitive inhibitor of tyrosinase from mushroom, human and murine sources. Tyrosine hydroxylase and 3,4-dihydroxyphenylalanine (DOPA) oxidase activities of tyrosinase from normal human melanocyte cell lysates were inhibited by aloesin in a dose dependent manner. In a percutaneous absorption study a finite dose of aloesin penetrated the skin slowly and was recovered primarily in the surface wash. Aloesin shows promise as a pigmentation-altering agent for cosmetic or therapeutic applications.

Fisiopatologia do melasma

“…11 O número de melanócitos diminui com a idade, em áreas não fotoexpostas, na proporção de 6 a 8% por década, sendo que as diferenças raciais na pigmentação não são devidas a uma marcante variação no número de melanócitos, mas sim no seu grau de atividade (síntese de melanina e melanossomas), na proporção dos subtipos de melanina (feomelanina e eumelanina), suas distribuições e envolvimento de fatores ambientais como a exposição solar, já que estimulam diretamente a síntese de melanina. 11,15 Nos melanócitos, a melanina produzida fica armazenada em estruturas intracitoplasmáticas específicas, denominadas melanossomas.…”

“…Em outras palavras, indiví-duos com maior pigmentação tendem a se queimar menos e bronzeiam mais do que indivíduos mais claros. 15,20,21 A feomelanina, por outro lado, tem um grande potencial em gerar radicais livres, em resposta à RUV, já que são capazes de causar danos ao DNA, dessa forma, podendo contribuir para os efeitos fototóxicos da RUV. Isto explica o porquê de as pessoas com pele clara, as quais contêm relativamente altas quantidades de feomelanina, apresentarem um risco aumentado de dano epidérmico, induzido por ultravioleta, inclusive neoplasias.…”

Modifying skin pigmentation – approaches through intrinsic biochemistry and exogenous agents

“…Concerns have been raised about a possible carcinogenic effect since kojic acid was associated with hepatic tumors when fed to p53 deficient mice [114]. Aloesin, a natural derivative of aloe vera, acts as a competitive inhibitor of DOPA oxidation and a non-competitive inhibitor of tyrosine hydroxylase activity [115]. In a clinical trial, a combination of aloesin and arbutin inhibited UV-induced melanogenesis [116].…”

Comparative Study on the Photostability of Arbutin and Deoxy Arbutin: Sensitivity to Ultraviolet Radiation and Enhanced Photostability by the Water-Soluble Sunscreen, Benzophenone-4

“…Numerous alternatives such as arbutin, deoxy arbutin, kojic acid, ascorbic acid, ellagic acid, aloesin, and p-coumaric acid have been developed to solve this problem. [8][9][10][11] Arbutin (hydroquinone-O--Dglucopyranoside, Fig. 1B), a derivative of hydroquinone, is a botanically derived compound found in cranberries, blueberries and wheat.…”