Wild rice hull antioxidants.

The methanol extract of wild rice hulls (WRH) showed antioxidant activity when added to ground beef, as evaluated by the content of thiobarbituric acid reactive substances (TBARS). Some fractions of the hull methanol extract (MeOH:H2O, 75:25) had strong antioxidant activity. The yield of the evaporated methanol extract was 2.51% of WRH. The crude methanol extract was fractionated according to hydrophobicity. Eluates of MeOH:H2O (50:50, 75:25) and absolute methanol had the strongest antioxidative activity in ground beef, as measured by the content of TBARS. Antioxidants were isolated from the 75:25 eluate and identified by mass spectrometry as 2,3,6-trimethylanisole (anisole); m-hydroxybenzaldehyde; 4-hydroxy-3-methoxybenzaldehyde (vanillin); and 4-hydroxy-3,5-dimethoxybenzaldehyde (syringaldehyde). Another compound identified, 2,3-dihydrobenzofuran, was a prooxidant.