IDENTIFICATION OF NEOCHLOROGENIC ACID AS THE PREDOMINANT ANTIOXIDANT IN POLYGONUM CUSPIDATUM LEAVES

To identify the predominant antioxidant compound in Polygonum cuspidatum leaves, the methanol extract of fresh samples were separated by liquid-liquid partitioning, octadecylsilyl sep-pak[R] cartridge and high-performance liquid chromatography. The main active compound was identified as (1R,3R,4S,5R)-3-{[(2E)-3-(3,4-dihydroxyphenyl)-2-propenoyl]oxy}-1,4,5-trihydroxycyclohexanecarboxylic acid (neochlorogenic acid) by nuclear magnetic resonance and liquid chromatographymass spectroscopic analysis. Its content was found to be 2.31 mg/g of fresh leaves. As shown by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and superoxide anion scavenging assays, the contributions of neochlorogenic acid as an antioxidant were 16.5% and 36.5%, respectively, suggesting that neochlorogenic acid is the predominant antioxidant in P. cuspidatum leaves. --Keywords: Polygonum cuspidatum, antioxidant, polyphenol, neochlorogenic acid--