However, their reversal multiple RF values were less than 15, and the ABCB1 inhibition activities were lower than the compounds (A1–A3, B1–B3, and C1–C3), indicating that the introduction of a benzyl group or benzyl group with three methoxy groups on the C ring was not conducive to improving the ABCB1 inhibition activity of cancer cells. Here, ABCB1 is linked to cancer.