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  • Title: Marker constituents of the natural antioxidant Eucalyptus leaf extract for the evaluation of food additives.
    Author: Amakura Y, Yoshimura M, Sugimoto N, Yamazaki T, Yoshida T.
    Journal: Biosci Biotechnol Biochem; 2009 May; 73(5):1060-5. PubMed ID: 19420705.
    Abstract:
    In order to establish the marker constituents of the natural antioxidant food-additive Eucalyptus leaf extract, the UV-absorbing constituents of two eucalyptus leaf extracts registered as food additives (eucalyptus A and B) were investigated. Several major peaks on the reversed-phase HPLC chromatogram of eucalyptus A were characterized as gallic acid, ellagic acid, 3-O-beta-D-glucuronides of quercetin and kaempferol, and a hydrolyzable tannin dimer, oenothein B, by direct comparison with authentic specimens isolated from Eucalyptus globulus leaves. A new gallotannin was found in the E. globulus leaf extract, and its structure was found to be 1,2,3,6-tetra-O-galloyl-beta-D-galactose. Two major peaks on the HPLC chromatogram of eucalyptus B were identified as gallic acid and ellagic acid, indicative of degradation products from hydrolyzable tannins in the leaves. Considering the evaluation of antioxidant activity by radical scavenging ability, a standardization of eucalyptus leaf extract, including the antioxidative polyphenol, oenothein B, is proposed.
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