Methanolic extract of Coptis japonica Makino reduces photosensitized oxidation of oils

Antioxidative activities of methanolic extracts of 47 plants on the methylene blue-sensitized or chlorophyll-sensitized photooxidations of linoleic acid were studied to select the plant species which possess the strong antioxidative activity in sensitized photooxidation of oil. The methanol extract of Coptis japonica Makino showed the strongest antioxidative activity in both methylene blue-sensitized and chlorophyll-sensitized photooxidations of linoleic acid. The study on the extracting solvent effects indicated that the antiphotooxidative components in the Coptis japonica Makino possess strong polar property, and are easily extracted with highly polar solvent (methanol). The methanol extract of Coptis japonica Makino was fractionated into three fractions (ethyl ether fraction, ethyl acetate fraction and butanol fraction) by liquid–liquid partitioning fractionation. Among the tested fractions, the butanol fraction showed strongest antioxidative activity in both chlorophyll-sensitized and methylene blue-sensitized photooxidation of linoleic acid. The butanol fraction also significantly inhibited the photooxidation of model food emulsion (50% soybean oil emulsion). The treatment with 0.3% (w/w) butanol fraction resulted in 64.9% inhibition of photooxidation of the model food emulsion during 60 h fluorescent light illumination.