Pleiocarpa pycnantha leaves and its triterpenes induce apoptotic cell death in Caco-2 cells in vitro.

Background: Recently, we reported that the crude fractions and pure triterpenes; ursolic acid (C1), 27-E and 27-Z p-coumaric esters of ursolic acid (C2, C3), together with a new triterpene 2,3-seco-taraxer-14-en-2,3-lactone [pycanocarpine (C4)] and its hydrolysed derivative - (2,3-seco-taraxen-4-hydroxy-14-en-2-oic acid) [pycanocarpene (C5)] from Pleiocarpa pycnantha leaves inhibit cell proliferation. However, there has not been any specific report on the use of Pleiocarpa pycnantha leaves and its constituents to kill colorectal adenocarcinoma cancer CaCo-2 cells. We performed in vitro study to evaluate the cytotoxic properties of the ethanolic extract of P. pycnantha P, compounds C2 and C3. A preliminary study of the potential mechanisms were also undertaken.

Methods: Cell viability was measured by WST-1 assay. The Apoptosis level was evaluated by staining with APOPercentage(™) dye and the induction of caspases 3/7 and 9 using Caspase-Glo(®) assays.

Results: The exposure of an ethanolic extract from the leaves of P. pycnantha (0.1-1000 μg/ml) and the isolated compounds C2 and C3 (6,25-100 μg/ml) to human colorectal cancer cells reduced the cell viability with an IC50 > 100, 40.9, 36.3 μg/ml for P, C2 and C3 respectively, after 24 h of incubation. The APOPercentage(TM) assay also showed a considerable increase in the percentage of apoptotic cells after 24 h; (25-38% for P, 5-23% for C2 and 6-47 % for C3). Caspase 3 was also activated which is a hallmark of apoptosis.

Conclusion: These findings suggest that the P. pycnantha and the isolated compounds induce cell apoptosis in human colorectal adenocarcinoma cells. A further study with other cell lines is also recommended.