[Isolation and identification of cynanester A from Cynanchum chinense R. Br].

Cynanester A (I) a new triterpenoid ester was isolated, together with lupeol acetate, lignoceric acid and beta-sitosterol, from Cynanchum chinense R. Br. (Asclepiadaceae). The mass spectrum suggested the presence of caproyl group and lupane skeleton with isopropenyl group in the molecule. Alkaline hydrolysis of I with 5% methanolic potassium hydroxide yielded lupeol Ia and n-caproic acid. The acid was esterified with MeOH-H2SO4 to afford methyl caproate, by GLC comparison with authentic sample. The acid was also identified by IR comparison. As above, the structure of cynanester A was established as lupeol caproate.