Screening of chemiluminescence constituents of cereals and DPPH radical scavenging activity of γ-oryzanol

The chemiluminescence (CL) constituents of cereals were detected by CL using the H2O2-acetaldehyde system. The cereals tested, such as rice, millet and sorghum, exhibited various levels of CL activity. The gamma -oryzanol fraction was extracted from brown rice and separated into four constituents by HPLC. The four constituents were identified as cycloartenyl ferulate, 24-methylenecycroartanyl ferulate, campesteryl ferulate and beta -sitosteryl ferulate. Free radical scavenging activities with 1,1-diphenyl-2-pierylhydrazyl (DPPH) and CL intensities of four constituents (gamma -oryzanol components) were measured and compared with that of gallic acid, which is a typical free radical scavenger. Four constituents: scavenged DPPH radicals and scavenging activities were proportional to CL intensities. Concentrations of four CL constituents required to quench 50% (IC50) of the free radicals ranged from 0.9 to 1.1 mmol/L. We demonstrated that measurement of CL intensities was a rapid and convenient method for screening DPPH radical scavenging activities of rice. Copyright (C) 2001 John Wiley & Sons, Ltd.