Comparative Study of Three Verbascum Species ( V . phlomoides , V . niveum and V . speciosum )—Chemical Characterization and Biological Activities

Objective For centuries, some mullein species (species of the genus Verbascum L.) have been used to treat respiratory diseases and internal and external infections and as excellent skin softeners. The healing properties of Verbascum species are the basis for their use in both traditional and conventional medicine. The present work aimed to identify and quantify the bioactive compounds of the flower extracts of V. phlomoides , V. speciosum , and V. niveum , and to determine their anti-inflammatory, antioxidant, and antimicrobial activities. Methods After spectrophotometric determination of the total phenolic content, the bioactive compounds were identified and quantified by HPLC, and the biological activities were assessed by in vitro methods. Results According to the obtained results, the major compounds in most of the tested extracts of Verbascum species were p-hydroxybenzoic acid, vanillic acid, verbascoside, aucubin, and catalpol. In both methods (DPPH and BCBT), the ethanol extracts showed stronger antioxidant activity than the water and propylene glycol extracts. All tested samples showed an anti-inflammatory effect in the BSA assay with an inhibition of protein denaturation of over 70%. The tested extracts were more active against Gram-positive than Gram-negative bacteria and showed the highest antimicrobial activity against Cutibacterium acnes and Streptococcus pneumoniae bacteria. Based on the results obtained, the tested species ( V. phlomoides , V. niveum , and V. speciosum ) are rich in polyphenolic acids, iridoids, and verbascoside and show comparable antioxidant, anti-inflammatory, and antimicrobial activity. Conclusion In conclusion, the studied Verbascum species can be considered a natural source of bioactive ingredients with great potential for the pharmaceutical industry.