High-performance liquid chromatographic determination of phenolic compounds in rice

A method has been developed for the determination of 6'-O-feruloyl sucrose, 6'-O-sinapoyl sucrose, ferulic acid, sinapinic acid, p-coumaric acid, chlorogenic (3-caffeoylquinic) acid, caffeic acid, protocatechuic acid, hydroxybenzoic acid, vanillic acid, and syringic acid in rice. The rice samples were extracted with 70% ethanol, filtered, and defatted. The defatted aqueous solution was subjected to solid-phase extraction using a C-18 silica gel cartridge; no analyte was lost in this procedure. The 70% acidic methanol elution was analyzed directly by HPLC and HPLC-ESI-MS. Phenolic compounds were separated with a C-18 reversed-phase column by gradient elution using 0.025% trifluoroacetic acid in purified water (A)-acetonitrile (B) (0 min, 5% B; 5 min, 9% B; 15 min, 9% B; 22 min, 11% B; and 38 min, 18% B) as the mobile phase at a flow rate of 0.8 ml/min. Detection limits ranged from 0.10 to 0.35 ng per injection (5 mul). Relative standard deviations of 0.22-3.95% and recoveries of 99-108% were obtained for simultaneous determination of these phenolic compounds. This method was applied to analysis of phenolic compounds in brown rice and germinated brown rice soaked in 32degreesC water for varying durations. (C) 2004 Elsevier B.V. All rights reserved.