Betulinic acid: isolation from Triphyophyllum peltatum and Ancistrocladus heyneanus, antimalarial activity, and crystal structure of the benzyl ester.

The known lupane-type triterpene betulinic acid (3) was isolated for the first time from Triphyophyllum peltatum and Ancistrocladus heyneanus. It was found to exhibit moderate to good in vitro antimalarial activity against asexual erythrocytic stages of the human malaria parasite Plasmodium falciparum. A first X-ray structure analysis succeeded after conversion into its benzyl ester 4.