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 (r ≥ 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.