Determination of (+)-Dihydrorobinetin as An Active Constituent of the Radical-Scavenging Activity of Asana (Pterocarpus marsupium) Heartwood:

Asana used in Ayurveda medicine originates from the heartwood of Fabaceae Pterocarpus marsupium. In our previous report, we demonstrated that a 50% ethanolic extract (PM-ext) of Asana was a promising candidate as a skin-whitening agent based on its anti-tyrosinase and antioxidative activities. Moreover, the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity of PM-ext was demonstrated and one of the active constituents was identified as oxyresveratrol. However, the potency of oxyresveratrol was low and the other active constituent has not yet been investigated. Activity-guided purification led us to isolate (+)-dihydrorobinetin (DHR). DHR had a potent DPPH radical-scavenging activity (half-maximal inhibitory concentration [IC50] = 1.3 mu M) and also showed suppressive activity of advanced glycation end products (AGEs) production (IC50 = 132 mu M), as well as superoxide dismutase (SOD)-like activity (half-maximal effective concentration=27 mu M). In a PM-ext, this is the first report to identify DHR and to demonstrate the suppressive activity of AGEs production and SOD-like activity of DHR. From these results, PM-ext containing DHR is a promising candidate as a multifunctional material with multiple anti-oxidant activities.