Simultaneous quantification and ADME prediction of AD-1 and its eight metabolites in rat feces, and screening of PARP-1 inhibitors through molecular docking

20(R)-25-methoxyl-dammarane-3 beta,12 beta,20-triol (CN Patent: 201,010,107,476.7, AD-1) is a promising anti-tumor compound, was isolated from total hydrolyzed saponins extracted from Panax notoginseng leaves. A sensitive and rapid method for the simultaneous detection of AD-1 and its 8 major metabolites in rat feces was developed in this study. AD-1 (20 mg/kg) was orally administered to male rats by gastric in-tubation. Then, the feces samples were collected. After addition of internal standard (Mifepristone), feces samples were pretreated by protein precipitation followed by liquid-liquid extraction. Chromatographic separation was performed on an Angela C-18 column with gradient elution using a mobile phase com-posed of acetonitrile and water (containing 5 mM ammonium acetate) at a flow rate of 0.3 mL/min. The analytes were detected without any interference from the multiple reaction monitoring (MRM) mode us-ing positive electrospray ionization. Calibration curves offered satisfactory linearity (r > 0.995) within the determined ranges. Both intra-day and inter-day variances were lower than 15%, and the accuracy was within 85-115%. The fecal excretion recoveries of AD-1 (M0), metabolite 1 (M1), M2, M3, M4, M5, M6, M7 and M8 were 41.36%, 0.62%, 6.20%, 0.50%, 6.99%, 2.07%, 1.86%, 0.41% and 0.29%, respectively. The ob-served excretion profiles for AD-1 and its metabolites after oral administration are helpful to understand the poor oral bioavailability of AD-1, and will aid further investigations of AD-1 as a pharmacologically active component. Moreover, the in silico ADME (Absorption, Distribution, Metabolism, Excretion) pre-dictions indicated that the metabolites were nontoxic and present passive gastrointestinal absorption. In previous studies, we found that M5, a metabolite of AD-1, has strong cytotoxicity against ovarian cancer cells. Further molecular docking studies showed that the most potent metabolite, M5, effectively binds to poly ADP-ribose polymerase-1 (PARP-1), which may provide novel solutions for treating ovarian cancer. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

A sensitive method was developed to detect AD-1 and its major metabolites in rat feces, showing the excretion profiles after oral administration which may help understand the poor bioavailability of AD-1. In silico ADME predictions suggest that the metabolites are non-toxic and have passive gastrointestinal absorption, while previous studies have shown a potent cytotoxicity of M5, a metabolite of AD-1, against ovarian cancer cells. Further molecular docking studies indicate that M5 effectively binds to PARP-1, providing potential novel solutions for treating ovarian cancer.