Isolation and Identification of Flavonoids in Licorice and a Study of Their Inhibitory Effects on Tyrosinase

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• 作者：Boqiang Fu ; Huan Li ; Xiaoru Wang ; Frank S. C. Lee ; and Shufen Cui
• 刊名：Journal of Agricultural and Food Chemistry
• 出版年：2005
• 出版时间：September 21, 2005
• 年：2005
• 卷：53
• 期：19
• 页码：7408 - 7414
• 全文大小：138K
• 年卷期：v.53,no.19(September 21, 2005)
• ISSN：1520-5118

文摘

Five different flavonoids were isolated from licorice after multistep chromatographic fractionation.The aim was to identify and characterize active components in licorice responsible for antibrowningactivities and to seek new tyrosinase inhibitors for applications as antibrowning and depigmentingagents in the food and cosmetic industries. The isolated flavonoids were identified as liquiritin,licuraside, isoliquiritin, liquiritigenin (from Glycyrrhiza uralensis Fisch.), and licochalcone A (fromGlycyrrhiza inflate Bat.) by UV, MS, ¹H NMR, and ¹³C NMR analyses. The inhibitory potencies andcapacities of these flavonoids toward monophenolase activity of mushroom tyrosinase wereinvestigated. The IC₅₀ values of licuraside, isoliquiritin, and licochalcone A for monophenolase activitywere 0.072, 0.038, and 0.0258 mM, respectively. A study of the mechanisms of monophenolaseinhibition by these flavonoids indicated that they are all competitive inhibitors. Different from the aboveflavonoids, no inhibitory activity was observed for liquiritin, whereas liquiritigenin activated themonophenolase activity as a cofactor. The inhibitory effect of licuraside, isoliquiritin, and licochalconeA on diphenolase activity with L-DOPA as the substrate was much lower than those with l-tyrosine.Results suggest that licuraside, isoliquiritin, and licochalcone A have the high potential to be furtherdeveloped into effective antibrowning and depigmenting agents.Keywords: Licorice; flavonoids; isolation; identification; tyrosinase; inhibition