Abstract
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•The total methanol extract of Iris germanica rhizomes was investigated.•Two new and 8 known compounds were isolated.•Their structures were established by various spectroscopic analyses.•The antioxidant and α-amylase inhibitory capacities of isolated compounds were evaluated.•The structure-activity relationship has been discussed.
Iris species are well recognized as wealthy sources of isoflavonoids. In the present study, phytochemical investigation of the rhizomes of Iris germanica (Iridaceae) procure the isolation of two new isoflavonoids namely, 8-hydroxyirilone 5-methyl ether (2) and 8-hydroxyirilone (3), along with eight known isoflavonoids: irilone 4′-methyl ether (1), irilone (4), irisolidone (5), irigenin S (6), irigenin (7), irilone 4′-O-β-d-glucopyranoside (8), iridin S (9), and iridin (10). The isolated flavonoids were structurally characterized with the assist of comprehensive spectroscopic analyses (UV, IR, 1D and 2D NMR, and HRMS) and comparing with the published data. They were estimated for their antioxidant and antidaibetic capacities using DPPH and α-amylase inhibition assays, respectively. Compounds 2, 3, and 4 exhibited prominent antioxidant activities with IC50 values of 12.92, 9.23, and 10.46μM, respectively compared to propyl gallate (IC50 7.11μM). Moreover, 2–5 possessed highest α-amylase inhibitory activity with % inhibition 66.1, 78.3, 67.3, and 70.1, respectively in comparison to acarbose (reference α-amylase inhibitor). Additionally, their structure-activity relationship has been discussed.