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Research Article

Tyrosinase inhibitory effects and inhibition mechanisms of nobiletin and hesperidin from citrus peel crude extracts

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Pages 91-98 | Received 17 Apr 2006, Accepted 09 Jul 2006, Published online: 04 Oct 2008
 

Abstract

The inhibitory effects of nobiletin and hesperidin from citrus peel crude extracts on tyrosinase diphenolase activity have been evaluated. IC50 of nobiletin and hesperidin were 1.49 mM and 16.08 mM, respectively and their inhibition mechanisms are competitive type with inhibition constant (Ki) 2.82 mM and noncompetitive type with Ki 9.16 mM, respectively. Crude extracts from citrus peel (C. unshiu Marc.) were extracted with 95% ethanol and fractionated by petroleum ether (PCPE). The ethanol phase (ECPE) was further desorbed from macroporous adsorption resin (FGRE). Their IC50 values were 8.09 mg/mL, 7.53 mg/mL and 4.80 mg/mL, respectively. Their inhibition of melanogenesis in B16 mouse melanoma cells was also evaluated. FGRE showed a significant inhibition (42.48% at 31.25 μg/mL, p < 0.01) while hesperidin showed almost no inhibition. Nobiletin and PCPE gave efficacious antiproliferation effects on the B16 mouse melanoma cell with IC50 values 88.6 μM and 62.96 μg/mL, respectively, through the MTT test. Hesperidin and other crude extracts showed very low cytotoxity to the B16 cell.

Acknowledgements

We sincerely thank Mr. Falin Wen for his warm help in cultivar authentication, Ms. Lei Jiang for the kind guidance on cell culture. We also thank all the colleagues such as Yongzhi Zhang, Baosong Teng, Zhaogui Chen, Zhiyong Liu for their warm supports in laboratory.

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