P-Glycoprotein Inhibitory Activity of Indonesian Medicinal Plants in Human Breast Cancer Cells

In order to examine their effects on the P-glycoprotein (P-gp) activity in human breast cancer cells, MCF-7/ADR, one hundred Indonesian plant extracts were screened. Among them, the five chloroform extracts of Calotropis gigantea, Curcuma aeruginosa, Merremia, Sindora sumatrana, and Zingiber cassumunar, showed the most potent P-gp inhibitory activity. When each of these extracts was treated together with the anticancer agent, daunomycin, they increased the cytotoxic activity of daunomycin up to IC∧50 values of less than 6.62 μM, which is a value with a positive control, verapamil. Also, other 15 plant extracts exhibited significant P-gp inhibitory activity with IC∧50 values between 6.62 and 13.20 μM.