ACTIVITY AND MECHANSIM STUDY OF NEW TYROSINASE INHIBITORS ISOLATED FROM TROPICAL PLANT ARCTIC SNOW (WRIGHTIA ANTIDYSENTERICA)

Abstract

Inhibition of tyrosinase is one of the most significant measurements in regulations of enzymatic browning and melanogenesis. The crude extract of traditional herbal medicine, Wrightia antidysenterica exhibited potent tyrosinase inhibitory activity with IC50 of 4.5 ± 0.4 µg/mL. Fourteen natural tyrosinase inhibitors including three alkaloids, two quercetin glycosides, four apigenin glycosides and five kaempferol glycosides have been isolated and characterized from W. antidysenterica using tyrosinase inhibitory activity assay guided column separation. The most potent tyrosinase inhibitor 4-hydroxyphenyl nitrite (4-HPN) shows an IC50 of 18.6 ± 1.8 µM, which is five times stronger than the positive control, kojic acid. It inhibits tyrosinase in a competitive mechanism with an inhibitor constant Ki of 8.27 µM. We also evaluated the anti-browning effect of W. antidysenterica’s crude extract on apple slices, and the statistic analytical results indicated that the crude extract of W. antidysenterica can significantly slow down the enzymatic browning and maintain an attractive appearance of fresh fruits.