MS/MS-based molecular networking accelerated discovery of germacrane-type sesquiterpene lactones from Elephantopus scaber L

Assisted by an MS/MS-based molecular networking guided strategy, six undescribed germacrane-type sesquiterpene lactones, namely scaberxones A-F, along with a known analog were obtained and characterized from Elephantopus scaber L. Their structures were unequivocally assigned by detailed spectroscopic analyses, NMR and ECD spectral calculations, and computer-assisted structure elucidation (CASE), complemented with single-crystal X-ray diffraction. All compounds were measured for their production of nitric oxide (NO) levels in lipopolysaccharide (LPS)-induced BV-2 microglial cells to assess their anti-neuroinflammatory activity. Scaberxone F showed the most potent inhibition of NO production at a concentration of 10 μM.