Withanolides Are Detected in Human Urine Following Oral Administration of a Withania somnifera Product

Ashwagandha (Withania somnifera (L.) Dunal; WS) is an adaptogenic herb, widely used in botanical dietary supplements. Plasma pharmacokinetics of selected withanolides, an important group of bioactive phytochemicals found in WS, have been described but no previous reports were found on their urinary excretion following WS ingestion. Healthy, older adults were administered oral doses of 240 or 480 mg of Shoden^®, a commercial extract of WS roots and leaves, and urine was collected over the subsequent 12 h. Using validated methods employing liquid chromatography coupled to multiple reaction monitoring mass spectrometry (LC-MRM-MS), we analyzed Shoden^® and participant urine samples for the presence of 11 withanolides for which standards were available. Only withaferin A (0.09 µmol/mg Shoden^®), withanoside IV (0.03 µmol/mg Shoden^®), and a mixture of 2,3-didehydrosomnifericin and 3R-viscosalactone B (0.19 µmol/mg Shoden^®) were present in Shoden^® powder in amounts greater than 0.01 µmol/mg Shoden^®. We detected four withanolides in participant urine: withaferin A; sominone, the aglycone of withanoside IV; 3R-viscosalactone B; and an abundant unidentified metabolite (WFNX), isomeric with 4-oxo withaferin A, and not detected in Shoden^®. Urinary recovery of the other 3 detected compounds was generally low (<3% of the amount in Shoden^®). These results provide new insights into the oral absorption, metabolism, and urinary excretion of withanolides found in WS and highlight additional withanolides to consider in future human pharmacokinetic and bioactivity studies of WS products.