Structural Characterization of Withanolide Glycosides from the Roots of Withania somnifera and Their Potential Biological Activities

Abstract

Withania somnifera (Solanaceae), commonly known as “ashwagandha”, is an ayurvedic medicinal plant that has been used for promoting good health and longevity. As part of our ongoing natural product research for the discovery of bioactive phytochemicals with novel structures, we conducted a phytochemical analysis of W. somnifera root, commonly used as an herbal medicine part. The phytochemical investigation aided by liquid chromatography-mass spectrometry (LC/MS)-based analysis led to the isolation of four withanolide glycosides (1–4), including one new compound, withanoside XII (1), from the methanol (MeOH) extract of W. somnifera root. The structure of the new compound was determined by nuclear magnetic resonance (NMR) spectroscopic data, high-resolution (HR) electrospray ionization (ESI) mass spectroscopy (MS), and electronic circular dichroism (ECD) data as well as enzymatic hydrolysis followed by LC/MS analysis. In addition, enzymatic hydrolysis of 1 afforded an aglycone (1a) of 1, which was identified as a new compound, withanoside XIIa (1a), by the interpretation of NMR spectroscopic data, HR-ESIMS, and ECD data. To the best of our knowledge, the structure of compound 2 (withagenin A diglucoside) was previously proposed by HRMS and MS/MS spectral data, without NMR experiment, and the physical and spectroscopic data of withagenin A diglucoside (2) are reported in this study for the first time. All the isolated compounds were evaluated for their anti-Helicobacter pylori, anti-oxidant, and anti-inflammatory activities. In the anti-Helicobacter pylori activity assay, compound 2 showed weak anti-H. pylori activity with 7.8% inhibition. All the isolated compounds showed significant ABTS radical scavenging activity. However, all isolates failed to show inhibitory activity against nitric oxide (NO) production in lipopolysaccharide-stimulated RAW 264.7 macrophage cells. This study demonstrated the experimental support that the W. somnifera root is rich in withanolides, and it can be a valuable natural resource for bioactive withanolides.

Protective Effects of Withagenin A Diglucoside from Indian Ginseng (Withania somnifera) against Human Dermal Fibroblast Damaged by TNF-α Stimulation

“…Interestingly, some withanolide glycosides exhibited antiviral activity, which suggests that the active withanolide glycosides can be therapeutic agents against coronavirus disease (COVID-19) [ 20 , 21 ]. In our recent phytochemical study on W. somnifera roots, we found that withanolide glycosides from W. somnifera show anti- Helicobacter pylori and antioxidant effects [ 22 ]. Therefore, withanolide glycosides can be important candidates to exhibit various promising biological effects that contribute to health benefits.…”

Withania somnifera L.: Phenolic Compounds Composition and Biological Activity of Commercial Samples and Its Aqueous and Hydromethanolic Extracts

“…Moreover, the methanolic leaf extracts were very effective against several bacteria present in pus samples of patients, including methicillin-resistant Staphylococcus aureus and Enterococcus spp., while Mehrota et al [ 67 ] reported that aqueous extracts of roots were effective against the same pathogen. Murugan et al [ 68 ] and Gebeyehu et al [ 69 ] suggested withaferin A as the main active component in leaf extracts against Pseudomonas aeruginosa , S. aureus , Streptococcus pneumoniae , Salmonella typhi , and E. coli ; while Ha et al [ 70 ] reported withanolide glycosides as the main bioactive compounds of roots. On the other hand, according to Balkrishna et al [ 71 ], fatty acids were responsible for the antibacterial effects of fixed seed oils on Salmonella enterica .…”

Antitumor Potential of Withanolide Glycosides from Ashwagandha (Withania somnifera) on Apoptosis of Human Hepatocellular Carcinoma Cells and Tube Formation in Human Umbilical Vein Endothelial Cells

“…Other known compounds were identified as withanoside III ( 2 ) [ 27 ], withagenin A diglucoside ( 3 ) (WAD) [ 20 , 33 ], withanoside IV ( 4 ) [ 27 ], and withanoside XII ( 4 ) [ 20 ] by comparing NMR spectroscopic data with those previously reported and MS data from LC/MS analysis.…”

“…Some withanolide glycosides exhibit antiviral activity and could be potential therapeutic agents against coronavirus disease (COVID-19) [ 18 , 19 ]. Based on our recent phytochemical study examining W. somnifera roots, withanolide glycosides possess anti- Helicobacter pylori and antioxidant effects [ 20 ]. Therefore, withanolide glycosides exhibit various promising biological effects that contribute to their health benefits.…”