Structure Elucidation and Antimicrobial Activities of Secondary Metabolites from the Flowery Parts of Verbascum mucronatum Lam

Objectives: To determine the secondary metabolites from Verbascum mucronatum Lam. and evaluate their antimicrobial activity.

Materials and methods: Antimicrobial activities of the isolated metabolites were determined using broth microdilutions against the bacteria (Escherichia coli ATCC 25922, Enterococcus faecalis ATCC 29212, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 29213) and fungi (Candida albicans ATCC 90028, Candida krusei ATCC 6258, Candida parapsilosis ATCC 90018).

Results: Four iridoid glycosides; ajugol (1), aucubin (2), lasianthoside I (3), catalpol (4), two triterpenic saponins; ilwensisaponin C (5), ilwensisaponin A (=mimengoside A) (6), and one phenylethanoid glycoside; verbascoside (=acteoside) (7) were isolated from the water soluble parts of the methanolic extract gained flowery parts of V. mucronatum Lam.

Conclusion: Within the obtained compounds, ajugol and ilwensisaponin A showed moderate antimicrobial activity, especially against fungi.

Keywords: Scrophulariaceae; Verbascum mucronatum Lam.; antimicrobial activity; secondary metabolites.