In vitro antiproliferative activity of crude extract and fractions of Brazilian red propolis

Abstract

Natural products are a major source of effective drugs in the treatment of cancer and often inspire the development of new potential agents. Propolis has been used empirically in folk medicine for centuries and there are many reports correlating numerous biological properties with variations on chemical composition. Among Brazilian propolis varieties, Brazilian red propolis (BRP), collected from Alagoas State, northeast of Brazil, presented a unique chemical composition enriched in isoflavones, suggesting new biological potential. This study aimed the antiproliferative evaluation of BRP crude ethanolic extract (EEP) and its fractions (hexane FH, ethyl acetate FEA, n-butanol FB, aqueous FA) on seven human cancer cell lines [U251 (glioma), MCF7 (breast), NCI/ADR-RES (resistant ovary), 786 – 0 (kidney), PC-3 (prostate), OVCAR-3 (ovary), K-562 (leukemia)] and one non-tumoral human cell line [HaCat (keratinocytes)]. After 48h-treatment, cell growth was determined by spectrophotometric measurements using sulforhodamine B assay. We used bioassay-guided fractionation, which is a proven method for the discovery of active principles from natural products, to isolate bioactive compounds from Brazilian red propolis ethanolic extract. EEP, FH and FEA showed a very similar antiproliferative profile (mean TGI 42.4, 43.0 and 53.2 µg/mL, respectively. TGI: concentration that elicits total growth inhibition) besides a lack of antiproliferative effect for FB and FA (mean TGI > 250 µg/mL). These results suggested that EEP anticancer potential effect could be related with medium and apolar compounds presents in FH and FEA. In this way, further studies are in progress aiming to identify the mechanism of action and the active principles of BRP.