Maclura cochinchinensis (Lour.) Corner. have been used as medicinal plant in tropical and subtropical countries for a long time. The stem of this plant has traditionally been used to treat, skin infection, fever and jaundice. Based on recent study, the compounds in this plant were found to be oxyresveratrol and morin [1],[2]. In present study, HPLC was performed using a Luna® 5 µm C18-column eluted with isocretic acetonitrile: 1.5 % formic acid (25:75) with a flow rate of 1 mL / min and detected at 352 nm. The inhibitory effect of the extracts on tyrosinase activity was determined spectrophotometrically with the degree of inhibition of L-DOPA. The HPLC method was illustrated to be precise with RSD < 1.5 %. The average recovery of oxyresveratrol and morin were 100.01 and 99.31 %, respectively. IC50 of M. cochinchinensis extract, oxyresveratrol, morin, and kojic acid (positive control) were found to be 7.91, 6.54, >500, and 92.25 µg / mL, respectively against tyrosinase. Five samples from various locations in Thailand of M. cochinchinensis stem extracts were analyzed and the average contents of oxyresveratrol and morin were 44.83 and 129.33 mg / g extract, respectively. This work would be useful as a guide for the standardization of M. cochinchinensis raw materials and their commercial products for antityrosinase activity.
Fig. 1 HPLC chromatogram of methanolic extract of M. cochinchinensis stem
