Ellagic acid rhamnosides from the stem bark of Eucalyptus globulus.
Four ellagic acid rhamnosides were isolated from the stem bark of Eucalyptus globulus. Their structures have been established on the basis of the analysis of their 1H NMR, 13C NMR, HMBC, IR and MS spectral data. The HMBC data of these compounds were most useful for their structure determinations, with these bring determined to be 3-O-methylellagic acid 3'-O-alpha-rhamnopyranoside, 3-O-methylellagic acid 3'-O-alpha-3''-O-acetylrhamnopyranoside, 3-O-methylellagic acid 3'-O-alpha-2''-O-acetylrhamnopyranoside, 3-O-methylellagic acid 3'-O-alpha-4''-O-acetylrhamnopyranoside, respectively. Their antioxidant activities were evaluated by measuring the inhibition of lipid peroxidation using rat liver microsomes, with IC50 values of 10.0-14.0 microg/ml.