Identification of metabolites in Withania sominfera fruits by liquid chromatography and high-resolution mass spectrometry

RATIONALE Withania somnifera is a rich source of biologically active secondary metabolites. Our earlier investigations on the fruits of this plant have yielded novel compounds, withanamides, with potent antioxidant activity and protective effect on β-amyloid-induced cytotoxicity in vitro. However, several minor compounds present in the fruits have not been characterized previously which may contribute to the observed biological activities. METHODS Liquid chromatography (LC) coupled with high-resolution mass spectrometry (HRMS) with data-dependent and targeted MS/MS experiments were conducted to elucidate the structure of observed metabolites. RESULTS A total of 62 metabolites identified included 32 withanamides, 22 withanolides, 3 steroidal saponins, 2 lignanamides, feruloyl tyramine, methoxy feruloyl tyramine and a diglucoside of hydroxyl palmitic acid. The structures of these compounds were proposed based on accurate masses of the molecular and fragment ions. Several of these new compounds identified from the profile were derived from withanamides with variations in aliphatic and/or glycosyl moieties. In addition, six new withanolides, a new hydroxy fatty acid diglucoside and several known compounds in the extract were identified. CONCLUSIONS The current study revealed the presence of several new and known compounds in Withania somnifera fruits. High-resolution MS and MS/MS experiments provide an extremely effective approach to derive the structures of plant secondary metabolites including isomeric compounds. Copyright © 2012 John Wiley & Sons, Ltd.