Antioxidant Activities and Phytochemicals of Leaf Extracts from 10 NativeRhododendronSpecies in Taiwan

Abstract

Rhododendron, one of the most famous ornamental plants in the world, is traditionally a medicinal plant. However, the potential bioactivities of nativeRhododendronin Taiwan have not been completely studied. In this study, the results revealed thatRhododendron pseudochrysanthumexhibited the best antioxidant activities among 10 nativeRhododendronspecies in Taiwan. Furthermore, based on a bioactivity-guided isolation principle, nine specific phytochemicals were isolated and identified as (2R,3S)-catechin (1), (2R,3R)-epicatechin (1′), (2R,3R)-dihydromyricetin 3-O-β-l-arabinopyranoside (2), (2S,3S)-taxifolin 3-O-β-l-arabinopyranoside (2′), (2R,3R)-taxifolin 3-O-β-l-arabinopyranoside (3), myricetin 3-O-β-d-glucopyranoside (3′), rutin (4), hyperoside (5), and quercitrin (6). Of these compounds,2and3were found to be major bioactive compounds, and their concentrations in then-butanol (BuOH) fraction were determined to be 52.0 and 67.3 mg per gram, respectively. These results demonstrated that methanolic extracts ofRhododendron pseudochrysanthumleaves have excellent antioxidant activities and great potential as a source for natural health products.