Chemical profile, antioxidant activity and stability in stimulated gastrointestinal tract model system of three Verbascum species

• Verbascum nigrum, V. phlomoides and V. thapsus extracts were analysed.
• The main secondary metabolite in all species was verbascoside.
• V. nigrum showed the strongest antioxidant activity and highest verbascoside content.
• Verbascoside was the major contributor to the antioxidant capacity of the extracts.
• In vitro simulated digestion showed variations in secondary metabolites contents.

The aim of this study was to determine the content of major secondary metabolites, namely, verbascoside, harpagoside, phenolic acids and flavonoids in Verbascum nigrum, Verbascum phlomoides and Verbascum thapsus methanol and water extracts by HPLC analysis and their antioxidant capacity. Also, the in vitro digestion simulation studies were performed on these extracts. Stability of individual compounds present in the extracts to digestive conditions was assessed using a simulated gastric and small intestinal model. Based on the obtained results, V. nigrum was marked as a plant with different secondary metabolites content, the highest total phenolics and phenolic acids amounts. Also, V. nigrum methanol extract showed the strongest antioxidant activity in different in vitro antioxidant methods. The main secondary metabolite in all species was verbascoside and its concentration was the highest in V. nigrum extract (118.60 mg/g of dry extract). Verbascoside exhibited strong antioxidant activity and was identified as the major contributor to the antioxidant activity of Verbascum species. After simulated in vitro digestion, verbascoside contents and antioxidant activities of the extracts were significantly decreased, whereas phenolic acids were quite stable during simulated digestion. This work provides valuable information about Verbascum plants and their pharmacologically important secondary metabolites suggesting that V. nigrum could serve as attractive source of antioxidants for application in food and pharmaceutical industry in forthcoming research.

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