Secondary metabolites from Verbascum bugulifolium Lam. and their bioactivities

Five iridoid glycosides catalpol (1), specioside (2), ajugol (3), ajugoside (4), 8-O-acetylharpagide (5), two phenylethanoid glycosides, verbascoside (6) and glucopyranosyl-(1→G_i-6)-martynoside (7), four flavonoids, luteolin (8), luteolin 7-O-β-glucopyranoside (9), luteolin 7-O-rutinoside (10), apigenin 7-O-rutinoside (11), quercetin 3-O-rutinoside (12) and β-sitosterol (13) were isolated from the aerial parts of Verbascum bugulifolium Lam. for the first time. Their structures were elucidated by NMR and MS experiments. The extracts, and the isolates were evaluated for their in vitro antioxidant (DPPH•, ABTS• and CUPRAC), anti-inflammatory (LOX inhibition) and antimicrobial activities. Compounds 6 and 8 showed the highest antioxidant activity in all tests, where luteolin (8) showed the relatively best anti-inflammatory activity compared to other samples with 54.1 ± 5.0% inhibition at 1 µg/mL. All the tested compounds showed weak antimicrobial activity against tested microorganisms. This is the first phytochemical and bioactivity study on V. bugulifolium.[Figure: see text].