Inula salicina L.: Insights into Its Polyphenolic Constituents and Biological Activity

In this study, UHPLC-HRMS analysis of the defatted methanol extract obtained from Inula salicina L. led to the identification of 58 compounds-hydroxycinnamic and hydroxybenzoic acids and their glycosides, acylquinic and caffeoylhexaric acids, and flavonoids and their glycosides. In addition, a new natural compound, N-(8-methylnepetin)-3-hydroxypiperidin-2-one was isolated and its structure was elucidated by NMR spectroscopy. The presence of a flavoalkaloid in genus Inula is described now for the first time. Chlorogenic acid was the main compound followed by 3,5-, 1,5- and 4,5-dicaffeoylquinic acids. The methanol extract was studied for its antioxidant potential by DPPH, ABTS, and FRAP assays and sun protective properties. In addition, a study was conducted to assess the effectiveness of the tested extract in inhibiting biofilm formation by Gram-positive and Gram-negative strains. Results from crystal violet tests revealed a notable decrease in biofilm mass due to the extract. The anti-biofilm efficacy was confirmed through the observation of the biofilm viability by live/dead staining. The obtained results showed that this plant extract could be used in the development of cosmetic products with antibacterial and sun protection properties.