New Screw Lactam and Two New Carbohydrate Derivatives from the Methanol Extract of Rice Bran

A new screw lactam and two new carbohydrate derivatives, oryzalactam (1), oryzasaccharide A (2), and oryzasaccharide B (3), have been isolated from the methanol extract of rice bran together with four other known compounds, including momilactone A (4), butyl beta-d-xylopyranose (5), ethyl beta-d-xylopyranose (6), and methyl beta-d-xylopyranose (7). The structures of these compounds were determined using a combination of spectroscopic methods and chemical analysis. This work represents the first recorded example of the isolation of compounds 1, 2, 3, 5, 6, and 7 from rice bran. The antioxidant experiments revealed that compound 1 possessed strong ABTS(+) (ABTS = 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid)) and DPPH (DPPH = diphenyl(2,4,6-trinitrophenyl) iminoazanium) radical scavenging with IC50 values of 33.38 +/- 1.58 and 40.20 +/- 1.34 mu M, respectively. Antimicrobial assays revealed that compound 4 showed high levels of selectivity toward Escherichia coli with a minimal inhibitory concentration value of 5 mu M.