Tigliane-Type Diterpene Esters from the Fruits of Shirakiopsis indica and Their Anti-HIV Activity.

Four new diterpene esters, shirakindicans A-D ( 1 - 4 ), along with eight related known diterpene esters ( 5 - 12 ), were isolated from the fruits of the Bangladeshi medicinal plant Shirakiopsis indica . The structures of 1 - 4 were elucidated by spectroscopic data analysis and electronic circular dichroism (ECD) calculations. Shirakindican A ( 1 ) was assigned as a tigliane-type diterpene ester possessing an unusual 6β-hydroxy-1,7-dien-3-one structure, while shirakindican B ( 2 ) exhibits a tiglia-1,5-dien-3,7-dione structure. The anti-HIV activities of the isolated diterpene esters were evaluated and showed significant activities for sapintoxins A ( 5 ) and D ( 11 ), with EC 50 values of 0.0074 and 0.044 μM, respectively, and TI values of 1 100 and 5 290. Sapatoxin A ( 12 ) also exhibited anti-HIV activity with an EC 50 value of 0.13 μM and a TI value of 161.