Antiproliferative effects of sea buckthorn (Hippophae rhamnoides L.) extracts on human colon and liver cancer cell lines

Sea buckthorn berries contain many bioactive compounds that have anticancer properties. To investigate whether the antiproliferative effects could be associated with the presence of certain compounds, a sequential extraction was performed. The extraction started with heptane followed by ethyl acetate, ethanol, and water. A second protocol using ethanol:water (1:1) was also used. The contents of the extracts were determined and their effects on cell proliferation were investigated in both Caco-2 and Hep G2 cells. The ethyl acetate fraction was exclusively found to contain high levels of ursolic acid, together with low amounts of phenolics. The ethanol:water extracts contained high levels of phenolic compounds and proanthyocyanidin, but little ursolic acid. When the antiproliferative effects were examined, the strongest inhibitory effect was found in the ethyl acetate extract for the Caco-2 cells and in the ethanol:water extract for the Hep G2 cells. The antiproliferative effects were in both cases dose-dependent and were in the case of the ethyl acetate extract associated with an increase in apoptosis. The results obtained show that the choice of extraction solvent is of considerable importance and that ursolic acid might be more important than the polyphenols in inhibiting the cancer cell proliferation.