A lupane triterpene from frankincense (Boswellia sp., Burseraceae).

A new lupane-type triterpene, 3alpha-hydroxy-lup-20(29)-en-24-oic acid, was isolated from the methanolic extract of "Erytrean-type" resin of commercial frankincense together with the known 3alpha-hydroxy-olean-12-en-24-oic acid (alpha-boswellic acid) and 3alpha-hydroxy-urs-12-en-24-oic acid (beta-boswellic acid). Their structures were characterized on the basis of chemical and spectral evidence including two dimensional NMR experiments and mass spectrometric techniques.