Withasomniferol D, a New Anti-Adipogenic Withanolide from the Roots of Ashwagandha (Withania somnifera)

Abstract

<i>Withania somnifera</i> (Solanaceae), well-known as 'Indian ginseng' or 'Ashwagandha', is a medicinal plant that is used in Ayurvedic practice to promote good health and longevity. As part of an ongoing investigation for bioactive natural products with novel structures, we performed a phytochemical examination of the roots of <i>W. somnifera</i> employed with liquid chromatography-mass spectrometry (LC/MS)-based analysis. The chemical analysis of the methanol extract of <i>W. somnifera</i> roots using repeated column chromatography and high-performance liquid chromatography under the guidance of an LC/MS-based analysis resulted in a new withanolide, withasomniferol D (<b>1</b>). The structure of the newly isolated compound was elucidated by spectroscopic methods, including one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) and high-resolution (HR) electrospray ionization (ESI) mass spectroscopy, and its absolute configuration was established by electronic circular dichroism (ECD) calculations. The anti-adipogenic activities of withasomniferol D (<b>1</b>) were evaluated using 3T3-L1 preadipocytes with Oil Red O staining and quantitative real-time polymerase chain reaction (qPCR). We found that withasomniferol D (<b>1</b>) inhibited adipogenesis and suppressed the enlargement of lipid droplets compared to the control. Additionally, the mRNA expression levels of adipocyte markers <i>Fabp4</i> and <i>Adipsin</i> decreased noticeably following treatment with 25 μM of withasomniferol D (<b>1</b>). Taken together, these findings provide experimental evidence that withasomniferol D (<b>1</b>), isolated from <i>W. somnifera</i>, exhibits anti-adipogenic activity, supporting the potential application of this compound in the treatment of obesity and related metabolic diseases.