Compounds with tyrosinase inhibition, elastase inhibition and DPPH radical scavenging activities from the branches of Distylium racemosum Sieb. et Zucc.

Twenty compounds were isolated from the ethanol extract of Distylium racemosum branches and their inhibitory activities on tyrosinase, elastase and free radicals evaluated. The isolated compounds were identified as dibenzofurans (1-4), abscisic acid (5), 6'-O-galloylsalidroside (6), catechin derivatives (7-11), gallic acid derivatives (12-14), tyrosol (15), flavonoids (16-18), lupeol (19) and 1,2,3,6-tetragalloylglucose (20). For study of tyrosinase inhibition activities, when compared with arbutin (IC(50) 48.8 μg/mL), four compounds (8, 11, 13, 17) showed higher activities, with IC(50) values of 4.8, 30.2, 40.5 and 37.7 μg/mL, respectively. For the elastase inhibition test, dibenzofuran 1 showed greater activity than the positive control, oleanolic acid (IC(50) 9.7 μg/mL), with an IC(50) of 7.7 μg/mL. In the studies on DPPH radical scavenging activities, five compounds (11, 12, 13, 14, 15) showed higher activities than ascorbic acid (IC(50) 5.0 μg/mL), with IC(50) values of 4.6, 3.9, 2.9, 3.8 and 4.7 μg/mL, respectively.