Cytotoxic Triterpenes from Salacia crassifolia and Metabolite Profiling of Celastraceae Species.

The new pentacyclic triterpene 11 β -hydroxypristimerin ( 1 ), along with the known metabolites pristimerin ( 2 ), 6-oxopristimerol ( 3 ) and vitideasin ( 4 ), were isolated from a Salacia crassifolia root wood extract, following a bioassay-guided fractionation approach. Both the extract and the purified triterpenes displayed pronounced cytotoxic activity against human cancer cell lines. The NCI-60 cell line screen revealed that compound 2 was the most active, with a mean GI50 of 0.17 μM, while compound 1 had a mean GI50 of 8.7 μM. A COMPARE analysis of the screening results showed that pristimerin is likely to be the main compound responsible for the cytotoxic activity of the extract (mean GI50 of 0.3 μg·mL−1 ). A targeted search for pristimerin and related derivatives using LC-MS/MS revealed the presence of pristimerin ( 2 ) and 6-oxopristimerol ( 3 ) in all Celastraceae species examined and in all plant parts tested, while vitideasin ( 4 ) was only detected in the genus Salacia .