Antioxidant and tyrosinase inhibition activities of the ethanol-insoluble fraction of water extract of Sapium sebiferum (L.) Roxb. leaves

The ethanol-insoluble fraction of water extracts of Sapium sebiferum leaves (new and fallen) were screened for their in vitro antioxidant and tyrosinase (TYR) inhibition activities. Fourier Transmission-Infra red was adopted for analysis of the major functional groups; common methods (scavenging of DPPH, ABTS, nitrite and hydroxyl radicals; ORAC; reducing power; β-carotene bleaching; and Fe²⁺ chelating assays) were employed to evaluate the antioxidant properties; and l-DOPA method was used to determine the TYR inhibition effects, and the copper chelating activities were also determined. Our results showed that fraction of water extracts of new and fallen S. sebiferum leaves have great antioxidant and TYR inhibition activities, even better than those of the positive control (BHT and arbutin). The TYR inhibition effect was significantly (P<0.05) and positive (r=0.8605) correlated with its copper chelating activity, which can be proposed as the mechanism of TYR inhibition. These results demonstrate that S. sebiferum leaves have great potential for being further studied and used, and no strict collection time limited. Altogether, potential antioxidant activity and TYR inhibitory property of S. sebiferum leaves could be applied to the industry as natural antioxidants and TYR inhibitors.