Mahanimbine isolated from Murraya koenigii inhibits P-glycoprotein involved in lung cancer chemoresistance

P-glycoprotein (P-gp), a transmembrane glycoprotein, is mainly involved in lung cancer multidrug resistance. Several P-gp inhibitors have been developed to enhance the efficacy of chemotherapeutics and overcome drug resistance. However, most of them failed in the clinical stages due to undesirable side effects. Therefore, there is a requirement to develop P-gp inhibitors from natural sources. Dietary spice bioactives have been well-known for their anticancer activities. However, their role in modulating the P-gp activity has not been well investigated. Therefore, we have screened for the potential bioactives from various spice plants with P-gp modulatory activity using computational molecular docking analysis. The computational analysis revealed several key bioactives from curry leaves, specifically mahanimbine, exhibited a strong binding affinity with P-gp. Unfortunately, mahanimbine is available with few commercial sources at very high prices. Therefore, we prepared a curry leaves extract and isolated mahanimbine by a novel, yet simple, extraction method that requires less time and causes minimum environmental hazards. After purification, structure, and mass were confirmed for the isolated com-pound by IR spectrum and LC-MS/MS analysis, respectively. In the mechanistic study, hydrolysis of ATP and substrate efflux by P-gp are coupled. Hence, ATP binding at the ATPase-binding site is one of the fundamental steps for the P-gp efflux cycle. We found that mahanimbine demonstrated to stimulate P-gp ATPase activity. Concurrently, it enhanced the intracellular accumulation of P-gp substrates Rhodamine 123 and Hoechst stain, which indicates that mahanimbine modulates the function of P-gp. In addition, we have analyzed the comple-mentary effect of mahanimbine with the chemotherapeutic drug gefitinib. We found that mahanimbine syner-gistically enhanced gefitinib efficiency by increasing its intracellular accumulation in lung cancer cells. Overall, mahanimbine has been shown to be a potent P-gp modulator. Therefore, mahanimbine can be further developed as a potential candidate to overcome chemoresistance in lung cancer.

Automated summary

This study identified a potential bioactive compound, mahanimbine, from curry leaves that showed strong binding affinity with P-gp and modulated its activity. The compound was extracted using a novel and simple method and its structure and mass were confirmed. Mahanimbine was found to stimulate P-gp ATPase activity and enhance the intracellular accumulation of P-gp substrates. It also synergistically enhanced the efficiency of the chemotherapeutic drug gefitinib in lung cancer cells. Overall, mahanimbine could be further developed as a potential candidate to overcome chemoresistance in lung cancer.