Phenolic Antioxidants from the Whole Plant of Phyllanthus urinaria

The 1,1‐diphenyl‐2‐picrydydrazyl (DPPH) assay on the extract of Phyllanthus urinaria L. (Euphorbiaceae) displayed considerable radical‐scavenging activity ( SC 50 =14.3 μg/ml). Further bioassay‐guided purification of the extract led to the isolation of a series of 15 phenolic compounds, including the ellagitannins 1 – 7 , the flavonoids 8 – 10 , and the simple hydroxylated (or glycosylated) aromatic acids 11 – 15 . Their structures were identified by spectroscopic analyses and comparison with authentic samples or literature data. The structure of repandinin B ( 1 ) was for the first time fully assigned by 1D‐ and 2D‐NMR experiments. The phenolic compounds 1, 3, 4, 6, 9, 11 , and 15 have not been isolated before from the title plant. The antioxidant activities and mushroom‐tyrosinase‐inhibitory activities of all compounds were determined by DPPH‐radical‐scavenging and mushroom‐tyrosinase‐inhibitory assays ( Table 2 ).