Antitrypanosomal activity of triterpenoids and sterols from the leaves of Strychnos spinosa and related compounds.

Fractionation of an antitrypanosomal lipophilic leaf extract from Strychnos spinosa led to the isolation of eight triterpenoids and sterols in this plant part for the first time. Two of these were found to possess in vitro antitrypanosomal activity, namely, saringosterol (14) and 24-hydroperoxy-24-vinylcholesterol (15), with IC(50) values of 7.8 +/- 1.2 and 3.2 +/- 1.2 microM, respectively. The latter compound was isolated from a plant source for the first time. A comparative study on the antitrypanosomal activity of the isolated triterpenoids and sterols and some related compounds has indicated that the presence of an oxygenated function at C-28 or an oxygenated side chain at C-17 seems to be important for the antitrypanosomal activity of triterpenoids and sterols, respectively.