Antioxidant constituents from the stem of Sorghum bicolor.

The EtOAc soluble fraction from the stem of Sorghum bicolor showed a strong free radical scavenging activity. Five major compounds were isolated from this fraction. They were identified by spectral data as methyl ferulate (1), methyl p-hydroxycinnamate (2), p-hydroxybenzaldehyde (3), tricin (4), and quercetin 3,4'-dimethyl ether (5). Among these compounds, 1 exhibited a strong, free radical scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH) with an IC50 value of 0.7 microM. We further studied the effects of these isolated compounds on the lipid peroxidation in rat liver microsomes induced by non-enzymatic method. All five compounds showed anti-lipid peroxidation activity (IC50 values of 0.5, 0.4, 0.3 and 0.3 microM, respectively).