Ellagic acid rhamnosides from the stem bark of Eucalyptus globulus

Four ellagic acid rhamnosides were isolated from the stem bark of Eucalyptu s globulus. Their structures have been established on the basis of the anal ysis of their H-1 NMR. C-13 NMR. HMBC, IR and MS spectral data. The HMBC da ta of these compounds were most useful for their structure determinations, with these bring determined to be 3-O-methylellagic acid 3 ' -O-alpha -rham nopyranoside, 3-O-methylellagic acid 3 ' -O-alpha -3 " -O-acetylrhamnopyran oside, 3-O-methylellagic acid 3 ' -O-alpha -2 " -O-acetylrhamnopyranosidc. 3-O-methylellagic acid 3 ' -O-a-4 " -O-acetylrhamnopyranoside, respectively . Their antioxidant activities were evaluated by measuring the inhibition o f lipid pel oxidation using rat liver microsomes. with IC50 values of 10.0 14.0 mug/ml. (C) 2001 Elsevier Science Ltd. All rights reserved.