Sunpollenol and Five Other Rearranged 3,4-<i>s</i><i>eco</i>-Tirucallane-Type Triterpenoids from Sunflower Pollen and Their Inhibitory Effects on Epstein−Barr Virus Activation

Abstract

Six new rearranged 3,4-seco-tirucallane-type triterpenoids (1-6) have been isolated from the diethyl ether extract of the pollen grains of sunflower (Helianthus annuus). These compounds were evaluated with respect to their inhibitory effects on the induction of Epstein-Barr virus early antigen (EBV-EA) induced by the tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA) in Raji cells. All of the compounds tested showed potent inhibitory effects on EBV-EA activation (97-100% inhibition at 1 x 10(3) mol ratio/TPA).