Thiotagetin B and tagetannins A and B, new acetylenic thiophene and digalloyl glucose derivatives from Tagetes minuta and evaluation of their in vitro antioxidative and anti-inflammatory activity

Abstract

The three new metabolites: thiotagetin B (2) [(Z)-1″-([2,2′-bithiophen]-5-yl)-8″-chloro-6″,11″-dimethylundeca-6″,10″-dien-2″-yn-9″-one], tagetannin A (9) [3,4-bis-(galloyl-3,5-dimethyl ether)-(α/β)-D-glucopyranose], and tagetannin B (10) [2,3-bis-(galloyl-3,5-dimethyl ether)-(α/β)-D-glucopyranose], along with ecliptal (5-formyl-α-terthiophene) (1), 5-(4-hydroxybut-1-ynyl)-2,2′-bithiophene (3), scopoletin (4), p-hydroxybenzoic acid (5), protocatechuic acid methyl ester (6), gallic acid (7), and patuletin 7-O-β-D-glucoside (8) were isolated from the aerial parts of Tagetes minuta L. (Asteraceae). Their structures were verified by extensive spectroscopic analyses as well as by comparison with literature data. The isolated compounds were evaluated for their antioxidant and anti-inflammatory activities using DPPH and enzyme-linked immunosorbent assays, respectively. Compounds 5–10 possessed the highest antioxidant potential with a scavenging activity (SCA) ≈ 74 to 93% of DPPH radicals. Moreover, 5–10 displayed significant anti-inflammatory potential, while 4 showed moderate activity. Compounds 5–10 exhibited significant decreases in NFκB p65, TNF-α and IL-6 levels at all tested concentrations.