Phase Ⅱ enzyme induction and anti-inflammatory effects of crude extracts and secondary fractions obtained from bran from five black glutinous rice cultivars

摘要

Methanolic extracts of bran from black glutinous rice cultivars were screened for potential health benefits using cellular bioassays for quinone reductase (QR) induction in murine hepatoma cells and inhibition of NO production in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages. Fractionation of the crude extract by semi-preparative HPLC afforded respective fractions enriched in phenolic acids, antho-cyanins and proanthocyanidins. The relative potency of QR induction was phenolic acids ＞ proantho-cyanidins ＞ anthocyanins, and the activity of the crude extract was conserved among the aggregate of these fractions. In contrast, all three fractions were more potent than the crude extract in terms of anti-inflammatory effect. This suggests synergism effects among anti-inflammatory agents through partial purification. Inhibition of macrophage NO production by binary mixtures of gallic acid or caffeic acid with the anthocyanin-rich fraction indicated potential synergism. These results warrant further efforts to identify the active agents and substantiate synergistic interactions through isobologram analysis.