New cycloartane triterpenes from bioactive extract of propolis from Pitcairn Island

Dichloromethane extract of propolis (DCME) originating from Pitcairn Island demonstrated potent cytotoxicity against triple-negative MDA-MB-231 human breast carcinoma cells. The results from MTT assay showed that DCME inhibits the growth of the cancer cells in a dose- and time-dependent manner and upon the cell growth inhibition propolis extract provoked apoptotic changes in the cell nuclei. A detailed chemical investigation of DCME led to the isolation of four new cycloartane triterpenes (1-4), along with 17 known compounds (5-21). The structures of the new compounds were elucidated by means of extensive analysis of their spectroscopic data and comparison with those reported for their analogues. In vitro antimicrobial activity of new compounds (1-4) along with the DCME against four human pathogens was evaluated. All tested constituents except compound 2 were highly active against Escherichia coli with MIC 64 μg/ml. Compound 1 exhibited high antifungal activity against Candida albicans with potency close to that of the positive control (amphotericin B). The DCME showed very good antimicrobial activity against Staphylococcus aureus, Escherichia coli and Candida albicans. This is the first study on propolis from Pitcairn Island.