Absolute bioavailability, dose proportionality, and tissue distribution of rotundic acid in rats based on validated LC-QqQ-MS/MS method

Preclinical pharmacokinetics, absolute bioavailability and dose proportionality evaluation of bioactive phytochemical Withanone in rats

Withanone (WN), a bioactive phytochemical isolated from the medicinal herb Withania somnifera, has shown multiple pharmacological and therapeutic successes, including neuroprotective and anti-cancer activities. However, detailed pharmacokinetic (PK) properties of pure WN were not well defined. Pharmacokinetic (PK) characteristics, dose proportionality, and absolute bioavailability of pure WN were explored in rats using an efficient, reliable, and sensitive LC-MS/MS assay to address this gap. The method shows excellent linearity over 0.5-500 ng/mL (r2 ≥ 0.99), is accurate, and requires less analysis time. A dose proportionality and absolute bioavailability of pure WN were determined in Sprague-Dawley (SD) rats through three ascending oral (10, 20, and 40 mg/kg) and single intravenous (5 mg/kg) PK studies. The peak concentration (Cmax) of WN was 60.53 ± 20.33, 116.30 ± 16.89, and 91.62 ± 6.20 ng/mL, corresponding to oral dosage of 10, 20, and 40 mg/kg, respectively. WN shows poor systemic exposure upon oral administration, leading to low oral bioavailability (<15 %). Additionally, the dose proportionality studies of WN revealed its saturable bioavailability and non-proportional systemic exposure over the dosage range of 10-40 mg/kg in rats. The obtained PK findings of this study would be valuable for better understanding the pharmacological effects of WN, dose regimen optimization for future studies, and relevance for clinical reference to support its future development as a potential therapeutic molecule.

UPLC-QTOF-MS Based Comparison of Rotundic Acid Metabolic Profiles in Normal and NAFLD Rats

Rotundic acid, the principal bioactive constituent of the herbal remedy "Jiubiying", has been considered as a candidate compound for treating non-alcoholic fatty liver disease (NAFLD). However, the in vivo and in vitro metabolism of rotundic acid has remained unclear. With the aim of elucidating its metabolic profile, a reliable approach that used ultra-high performance liquid chromatography combined with quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) was applied for screening and identifying rotundic acid in vivo (plasma, feces, urine, and liver tissue of normal and NAFLD model rats) and in vitro (rat liver microsomes) metabolites. Herein, 26 metabolites of rotundic acid were identified, including 22 metabolites in normal rats, 20 metabolites in NAFLD model rats, and eight metabolites in rat liver microsomes. Among them, 17 metabolites were identified for the first time. These data illustrate that the pathological status of NAFLD affects the metabolism of rotundic acid. Furthermore, the major pathways of metabolism included phase Ⅰ (demethylation, desaturation, etc.) and phase Ⅱ (sulfation and glucuronidation) reactions, as well as a combined multiple-step metabolism. This work provides important information on the metabolism of rotundic acid and lays the foundation for its future clinical application.