Abstract
Propolis, one of the oldest medicines, attracts much attention from the medical community, because of its antibiotic and anti-tumor activities. There are accumulating evidences indicating that propolis ingredients such as caffeic acid phenyl ethyl ester (CAPE) and quercetin (QU) have a variety of novel action including neuroprotective action in addition to well-known anti-tumor activities. It is of significance for the propolis study to elucidate molecular mechanisms underlying these novel actions of propolis. Propolis itself, however, cannot be used in in-vitro experiments that utilize cultured tissues because of its poor solubility in water. To circumvent this problem, we have carried out an in-vitro study of anti-tumor action of Brazilian propolis using water-dispersible form of propolis (WDP). Using rat C6 glioma cells, we have demonstrated a dose-dependent anti-tumor action of WDP. The effects of WDP are compared with those of active ingredients of propolis. Both QU and CAPE were found to inhibit cell-growth of C6 cells in serum-supplemented DMEM. However, QU failed to induce C6 cell death after serum-deprivation, while both WDP and CAPE killed C6 cells. Thus, the inhibition of C6 growth induced by WDP could be accounted on the basis of cytotoxic action of CAPE. QU does not kill C6 cells, but inhibits cell proliferation. [J Physiol Sci. 2006;56 Suppl:S226]
