Tyrosinase kinetic inhibition of active compounds from intsia palembanica

Abstract

Intsia palembanica is the most potential plant having tyrosinase inhibitor over 30 Indonesian plants that have been searched. It's active compound namely (-)-robidanol, (+)-epirobidanol and 4′-dehydroxyrobidanol had been identified and showed the tyrosinase inhibitory activity. The study aims to obtain the kinetic enzyme inhibition type of the three active compounds. About 3 g of I. palembanica methanol extract was fractionated using n-hexane soluble part, ethyl-acetate soluble part and aqueous soluble part. Compounds were isolated for the most active part (ethyl- acetate soluble part) by silica gel column chromatography. Purification of fractions was performed using preparative High Performance Liquid Chromatography (HPLC). Kinetic inhibition against tyrosinase on monophenolase and diphenolase were analyzed by Lineweaver-Burk plot. The results showed that three active compounds showed different kinetic inhibition type on monophenolase and diphenolase. The kinetic characteristics of (-)-robidanol, the most active inhibitor, on monophenolase were Km increased and Vmax did not changed while on diphenolase were Vmax decreased and Km did not change. In conclusion, (-)-robidanol is a competitive inhibitor for monophenolase and a non-competitive inhibitor for diphenolase. The kinetic data is useful for further research on mechanism of action of the whitening agent that will be formulated. © 2012 Academic Journals Inc.