Antioxidative Phenolic Compounds from Japanese Barnyard Millet (<i>Echinochloa utilis</i>) Grains

Abstract

Three antioxidative phenolic compounds, one serotonin derivative and two flavonoids, were isolated from an ethanol extract of Japanese barnyard millet (cv. Kurohie) grains by Sephadex LH-20 chromatography and preparative high-performance liquid chromatography. Their structures were established to be N-(p-coumaroyl)serotonin, luteolin, and tricin on the basis of spectrometric data from (1)H and (13)C and two-dimensional nuclear magnetic resonance techniques, fast atom bombardment mass spectrometry, and Fourier transform infrared spectrophotometry. N-(p-Coumaroyl)serotonin exhibited a strong antioxidant activity almost equivalent to that of butylated hydroxyanisole at the same concentration (w/v). Although the antioxidant activity of luteolin was lower than that of N-(p-coumaroyl)serotonin, it was nearly equal to that of quercetin, whereas the activity of tricin was lower than that of luteolin. All of them were newly isolated from Japanese barnyard millet grains.