Discovery of traditional Chinese medicine monomers and their synthetic intermediates, analogs or derivatives for battling P-gp-mediated multi-drug resistance.

P-glycoprotein (P-gp)-mediated multi-drug resistance (MDR) is a well-documented and predominant phenotype hampering patients' response to cancer chemotherapy. Although the past several decades have witnessed the development of three generations of P-gp inhibitors, they have not lived up to the high expectations owing to their drawbacks, as exemplified by limited efficacy, drug-drug interactions (DDIs) and severe untoward reactions. The discovery of artemisinin is a testimony of the importance of traditional Chinese medicine (TCM) in innovative drug discovery. In search for a new generation of chemo-sensitizers, P-gp modulators originated from TCM have attracted increasing concern in the research community. In addition to identify TCM monomers or their synthetic intermediates as P-gp modulators, massive medicinal chemistry efforts have been made in discovering promising structural analogs and derivatives of them. Among these, compounds with dual role both as P-gp inhibitor and cytotoxic agent have continuously emerged. Hence, in this article, we will mainly enumerate the representative work conducted in the discovery of TCM monomers and their synthetic intermediates, analogs or derivatives as reversers of P-gp-mediated MDR.