Isolation of Four New Indole-3-acetic Acid (IAA) Oxidative Metabolites, a Pair of Diasteromers 5-O-β-D-glucopyranosyl 3,5-Dihydroxy-2-indolinone-3-acetic Acid and 5-O-β-D-cellobiosyl 3,5-Dihydroxy-2-indolinone-3-acetic Acid from Rice Bran

Abstract

Four new metabolites related to IAA (indole-3-acetic acid) were isolated from an aqueous methanol extract of rice bran and were elucidated by spectroscopic methods to be a pair of diastereomers of 5-O-β-D-glucopyranosyl 3,5-dihydroxy-2-indolinone-3-acetic acid (A-1 and A-2) and of 5-O-β-D-cellobiosyl 3,5-dihydroxy-2-indolinone-3-acetic acid (B-1 and B-2). Compound B-1 was also a diastereomer of compound B-2 at the C₃ position with an asymmetric carbon atom on an indolinone skeleton, like the relationship between compounds A-1 and A-2.

• rice bran
• IAA oxidative metabolite
• cellobioside
• diastereomer