Potential antitumor-promoting diterpenoids from the stem bark of Picea glehni

A novel rearranged labdane-type diterpenoid, 19(4-->3)abeo-8alpha, 13(S)-epoxylabda-4(18),14-diene (1), and two new abietane-type diterpenoids, 19-nor-abieta-4(18),8,11,13-tetraen-7-one (2) and 12-hydroxydehydroabietic acid (3) were isolated from the stem bark of Picea glehni, together with seven known diterpenoids-13-epimanoyl oxide (4), dehydroabietic acid (5), (11E)-14, 15-bisnor-8alpha-hydroxy-11-labden-13-one (6), abieta-8,11, 13-trien-7-one (7), 9alpha,13alpha-epidioxyabiet-8(14)-en-18-oic acid (8), 9,10alpha-epoxy-9,10-seco-abieta-8,11,13-trien-18-oic acid (9), and methyl 15-hydroxy-7-oxo-dehydroabietate (10). Compounds 5-8 and 10 showed potent inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by the tumor promoter 12-O-tetradecanoylphorbol 13-acetate.