Tagenols A and B: New lipoxygenase inhibitor flavonols from Tagetes minuta

Abstract

Phytochemical investigation of the methanolic extract of Tagetes minuta L. (Asteraceae) aerial parts afforded two new flavonol derivatives: tagenol A (quercetagetin-8-hydroxy-3,6,4′-trimethy ether) (1) and tagenol B (quercetagetin-8-hydroxy-3-methoxy-6-O-β-d-glucopyranoside) (4), together with three known flavonoids: quercetin-3,6-dimethyl ether (2), quercetin-3-methyl ether (3), and axillarin-7-O-β-d-glucopyranoside (5). Their structures were identified by UV, IR, 1D (1H and 13C), 2D (1H-1H COSY, HSQC, and HMBC) NMR, and HRESIMS spectral data as well as comparison with literature data. The isolated compounds were evaluated for their lipoxygenase inhibitory and antioxidant activities. Compounds 1-5 displayed moderate lipoxygenase inhibitory activities with IC50 values of 12.2, 9.4, 7.1, 5.8, and 4.2 μM, respectively compared to indomethacin (IC50 0.9 μM). Moreover, they displayed promising antioxidant activities with IC50 values of 14.9, 14.3, 13.5, 12.7, and 11.2 μM, respectively using DPPH assay compared to propyl gallate (IC50 7.38 μM).