NMR-based metabolomics of Verbascum species and evaluation of their antioxidant and anti-inflammatory activities

Mulleins (Verbascum L., Scrophulariaceae) have been used in the traditional folk medicine since time immemorial for treatment of a wide range of human ailments, inter alia bronchitis, tuberculosis, asthma, and different inflammations. We applied an NMR-based metabolomics to study metabolic differentiations of five mullein species. ¹H NMR fingerprinting in combination with principal component analysis allows chemical classification of Verbascum species in two groups: group A (V. phlomoides and V. densiflorum) and group B (V. xanthophoeniceum, V. nigrum and V. phoeniceum). In addition, it was found that the plants in group B synthesize higher amounts of bioactive iridoid (e.g. pharmaceutically-important harpagoside) and phenylethanoid glycosides (verbascoside, forsythoside B and leucosceptoside B). The antioxidant and anti-inflammatory activities of Verbascum plants were evaluated using several in vitro and in vivo assays. Furthermore, the iridoid glycoside harpagoside has been thoroughly evaluated in models of acute and chronic inflammations (e.g. zymosan-induced arthritis in mice). Based on the obtained results it can be concluded that Verbascum plants could serve as attractive mines of powerful antioxidant and anti-inflammatory compounds for the food, cosmetics, and pharmaceutical industries.