First report on the pharmacokinetic profile of nimbolide, a novel anticancer agent in oral and intravenous administrated rats by LC/MS method

Nimbolide is a novel, natural compound with promising potential as a drug candidate for anticancer activity. It is isolated from the Indian traditional medicinal plant Azadirachta indica popularly known as neem. The present study was undertaken to explore the oral bioavailability and pharmacokinetic characteristics of nimbolide in rats using the LC/QTOF/MS method. A simple protein precipitation method using acetonitrile was employed for extracting nimbolide from rat plasma. The chromatographic separation of nimbolide and the internal standard (regorafenib) was attained on an Aquity BEH C18 column (100 x 2.1 mm, 2.7 mu m), using ACN and 0.1% of formic acid in water as mobile phase components in a gradient elution mode at a flow rate of 0.45 mL/min over a short run time of 4 min. A mass detection was carried out using target ions of [M + H](+) at m/z 467.2074 for nimbolide and m/z 483.0847 for the internal standard. The LC/MS method was validated and all the parameters were found well within the specified limits. The calibration curve was constructed in the range of 1-1000 ng/mL. The method shows good accuracy (91.66-97.12%) and precision (intra 2.21-6.92% CV and inter-day 2.56-4.62% CV). This developed LC/MS method was effectively applied to the pharmacokinetic study of nimbolide upon oral and intravenous administration in rats. In concordance with its physicochemical properties and high lipophilicity, we found that it shows poor oral absorption at different doses (10, 30 and 50 mg/kg). As expected, higher plasma levels were observed upon intravenous (10 mg/kg) administration. This method can be extended for evaluation of drug interaction and drug metabolism in rats as well as in humans. Moreover, our rapid and sensitive method may cater the need to accelerate the preclinical formulation development and lead optimization for future drug development of this potent anticancer agent. Further, our oral bioavailability studies demonstrated that nimbolide possesses poor oral absorption, which could be the probable reason for the delay in therapeutic translation of this promising agent for clinical use.