ANTIOXIDANT ACTIVITY OF TANNINS AND FLAVONOIDS IN EUCALYPTUS-ROSTRATA

Antioxidant activity of an extract from Eucalyptus rostrata was the highest among 16 Eucalyptus species tested. From the leaves of Eucalyptus rostrata nine active compounds were isolated: 1,2,6-tri-O-galloyl-beta-D-glucose and tellimagrandin 1 as tannins; spiraeoside, hyperoside, isoquercitrin, and myricetin 3-O-alpha-L-arabinopyranoside as flavonol glycosides; quercetin 3-O-alpha-arabinopyranoside-2''-gallate, kaempferol 3-O-a-arabinopyranoside-2''-gallate, quercetin 4'-O-beta-D-glucopyranoside-6''-gallate as acylated flavonol glycosides. Antioxidant activity of the tannins and acylated flavonol glycosides, all with galloyl groups, was much higher than that of a synthetic antioxidant. Two of the compounds, spiraeoside and quercetin 4'-glucosylgallate, showed high superoxide dismutase activity.