Depigmentation of melanocytes by isopanduratin A and 4-hydroxypanduratin A isolated from Kaempferia pandurata ROXB

This study was carried out to investigate the in vitro effects of isopanduratin A and 4-hydroxypanduratin A isolated from Kaempferia pandurata ROXB. on melanin biosynthesis and tyrosinase activity. Two chalcone compounds, isopanduratin A and 4-hydroxypanduratin A, were isolated from the ethyl acetate fraction of ethanol extract as the active principles. Compared with phenylthiourea (IC₅₀=34.3 μM) as a positive control, the depigmentation IC₅₀ values for isopanduratin A and 4-hydroxypanduratin A were 10.6 μM and 23.2 μM, respectively. The compounds also significantly inhibited the activity of tyrosinase, the enzyme that converts DOPA (3,4-dihydroxyphenylalanine) to dopachrome in the biosynthetic process of melanin. The IC₅₀ values of isopanduratin A and 4-hydroxypanduratin A for tyrosinase were 10.5 μM and >30 μM, respectively, while that of phenylthiourea was 47.6 μM. The tyrosinase protein level was also significantly decreased by isopanduratin A and 4-hydroxypanduratin A. The results indicate that isopanduratin A and 4-hydroxypanduratin A isolated from K. pandurata ROXB. are promising compounds that could be useful for treating hyperpigmentation as skin-whitening agents.