Antioxidant Activities and Phytochemical Study of Leaf Extracts from 18 Indigenous Tree Species in Taiwan
The objective of this study is to assess antioxidant activities of methanolic extracts from the leaves of 18 indigenous tree species in Taiwan. Results revealed that, among 18 species,Acer oliverianumexhibited the best free radical scavenging activities. The IC50values were 5.8 and 11.8 μg/mL on DPPH radical and superoxide radical scavenging activities, respectively. In addition,A. oliverianumalso exhibited the strongest ferrous ion chelating activity. Based on a bioactivity-guided isolation principle, the resulting methanolic crude extracts ofA. oliverianumleaves were fractionated to yield soluble fractions of hexane, EtOAc, BuOH, and water. Of these, the EtOAc fraction had the best antioxidant activity. Furthermore, 8 specific phytochemicals were isolated and identified from the EtOAc fraction. Among them, 1,2,3,4,6-O-penta-galloyl-β-D-glucopyranose had the best free radical scavenging activity. These results demonstrate that methanolic extracts and their derived phytochemicals ofA. oliverianumleaves have excellent antioxidant activities and thus they have great potential as sources for natural health products.