An in vitro screening experiment of 45 methanolic plant extracts was carried out to investigate the inhibition of P-glycoprotein (P-gp) in MCF-7R cells. The investigation was carried out using standard functional assay with rhodamine 6G as the fluorescent probe and reserpine, a known inhibitor of P-glycoprotein pump, was used as a reference drug. The results revealed that out of the 45 plant extracts tested, 3 extracts i.e. Bauhinia thoningii, Clerodendrum myricoides and Rhus natalensis exhibited pronounced activity at the concentration of 100 µg/ml. In comparison to the negative control, B. thoningii, C. myricoides and R. natalensis extracts inhibited the pump by a factor of about 2.5, 4 and 4.3, respectively. The remaining 42 extracts did not show any activity. The reference drug reserpine (20 μM) inhibited the pump by a factor of about 11. These preliminary results indicate that the inhibition of P-gp in MCF-7R cells is through a concerted action of compounds present in the extracts and that if isolated might be effective P-gp pump inhibitors in the treatment of cancer.
Keywords: plant extract, P-glycoprotein inhibition; rhodamine 6G; MCF-7R cells
East and Central African Journal of Pharmaceutical Sciences Vol. 7 2004: 16-22