Isolation, Structural Elucidation, and Inhibitory Effects of Terpenoid and Lipid Constituents from Sunflower Pollen on Epstein−Barr Virus Early Antigen Induced by Tumor Promoter, TPA

Abstract

Eight fatty acid esters of triterpene alcohols (1-8), four free triterpene alcohols (9, 12, 17, and 18), four diterpene acids (19-22), two tocopherol-related compounds (23 and 24), four estolides (25-28), three syn-alkane-4,6-diols (29-31), one 1,3-dioxoalkanoic acid (32), and one aliphatic ketone (33), along with the mixture of free fatty acids, were isolated from the diethyl ether extract of the pollen grains of sunflower (Helianthus annuus). Among these compounds, 14 (2-8, 12, 23, 25-28, and 33) were new naturally occurring compounds, and their structures were determined on the basis of spectroscopic methods. Twenty-four terpenoids and lipids (1-4, 6-9, 12, and 19-33) and six free triterpene triols (10, 11, and 13-16), derived from their fatty acid esters (2, 3, and 5-8) by alkaline hydrolysis, 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, which is known to be a primary screening test for antitumor promoters. Among the 30 compounds tested, 21 compounds possessing a di- or a polycyclic ring system in the molecule (1-4, 6-16, and 19-24) showed potent inhibitory effects on EBV-EA induction (91-100% inhibition at 1 x 10(3) mol ratio/TPA).