Abietane diterpenoids from Isodon amethystoides and their biological activities.

Seven undescribed abietane diterpenoids [abietamethinols A-G (1 – 7)] were isolated from the twigs and leaves of Isodon amethystoides. Their structures were elucidated on the basis of spectroscopic methods including 2D NMR, and they were further confirmed by X-ray crystallographic data. Lophanic acid was considered as the precursor of 1 – 7 in the biosynthesis pathway hypothesis. These compounds were evaluated for their cytotoxic, anti-bacterial and anti-AIV (avian influenza virus) activities. Compound 5 showed 42.9% inhibitory activity against the cancer cell line SMMC-7721 at the concentration of 40 μM, 3 and 4 could inhibit the bacterial growth of Streptococcus sobrinus by 55.3% and 63.2% at the concentrations of 148.6 and 141.9 μM, respectively, and 4 was demonstrated with antiviral activity against AIV with the inhibitory effect of 68.4% at 25 μM. Abietamethinols A-G, seven undescribed abietane diterpenoids with unique γ -lactone ring system were isolated from the twigs and leaves of Isodon amethystoides. Among them, compound 4 showed inhibitory effect against Streptococcus sobrinus and AIV respectively. [Display omitted] • Abietane diterpenes (abietamethinols A-G) were isolated from Isodon amethystoides. • Abietamethinols C and D could inhibit the growth of streptococcus sobrinus. • Abietamethinol D was found to inhibit the replication of AIV. • The structures of all isolates were confirmed by the X-ray crystallographic data. • A plausible biosynthetic pathway of abietamethinols A-G was proposed. [ABSTRACT FROM AUTHOR]