Atricephenols A and B, two phenolic compounds from Indigofera atriceps Hook.f. (Fabaceae)

The phytochemical investigation of a previously unstudied species of the genus Indigofera, I. atriceps Hook.f. was undertaken and two new phenolic compounds, atricephenols A (1) and B (2) were isolated, along with nine known secondary metabolites viz., (-)-melilotocarpan D (3), genistein (4), melilotocarpan A (5), maackiain (6), p-hydroxybenzaldehyde (7), bornesitol (8), β-sitosterol (9), sitosterol-3-O-β-D-glucopyranoside (10) and stigmasterol-3-O-β-D-glucopyranoside (11). Their structures were elucidated by extensive NMR spectroscopic analyses and HRESIMS, and by comparing their data with those reported in the literature. Compounds 1, 4, 7-11 were tested for their antibacterial efficacies and for their potential to inhibit the enzyme urease. Compounds 7 and 9 showed significant antibacterial activity against Salmonella typhi (ZOIs of 13 and 15 mm, respectively), while the best urease inhibition was measured for compound 9 with an IC₅₀ value of 18.6 µM, which is higher than that of the potent inhibitor, thiourea (IC₅₀ = 21.5 µM).