Antioxidant and Antimicrobial Phenolic Compounds from Setaria viridis

A chemical study of the 80% aqueous acetone extract of aerial parts of Setaria viridis led to the isolation of three new naphthol rhamnosides, 8-O-alpha-L-rhamnosyl-beta-sorigenin (1), 6-hydroxy-8-O-alpha-L-rhamnosyl-beta-sorigenin (2), and 6-methoxy-8-O-alpha-L-rhamnosyl-beta-sorigenin (3), together with nine (4-12) known compounds. Their structures were established on the basis of spectroscopic data, including IR, MS, 1D, and 2D NMR. All the 12 compounds were tested for their antioxidant activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, as well as antimicrobial activity. Compounds 1-3 exhibited strong antioxidant activity with IC50 values of 10.5, 13.8, and 15.3 mu M, respectively, and modest activity against Staphylococcus aureus (ATCC 29213).