In-vitro and in-silico antioxidant, α-glucosidase inhibitory potentials of abutilins C and D, new flavonoide glycosides from Abutilon pakistanicum

Abstract

The methanolic extract along its various fractions Abutilon pakistanicum were analyzed to find total phenolic, flavonoids contents followed by antioxidant and α-glucosidase inhibitions of isolated pure constituents. The total content of phenolics and flavonoids was consistently higher in CH2Cl2 (54.89 and 56.06 mg/g extract respectively) compared with n-hexane, ethyl acetate, n-butanol and H2O portions (ranging between 37.81–54.89 and 38.11–56.06 mg/g extract). In order to determine active biological ingredients from CH2Cl2 subportions, extensive advanced chrotapographic separation methods resulted isolation of new flavonoid glycosides namely abutilins C-D (1–2). The structures of these constituents were interpreted by spectroscopic data including FAB-MS, ESI-MS, 1D and 2D-NMR experiments. Both flavonoid (1–2) were evaluated against antioxidant and α-glucosidase inhibitory assay. The antioxidant potential of dichloromethane extract and abutilins C-D (1–2) were determined using DPPH and nitric oxide radial scavenging assays. The abutilins C displayed significant inhibition, with IC50 values 41.66 (DPPH), 39.04 (NOS) µg/mL, using positive control ascorbic acid and quercetin respectively. Inhibitory effects of flavonoids against enzyme α-glucosidase were also investigated and abutilins C showed significant activity with IC50 values 8.27 µg/mL compared with positive control ascarbose (IC50, 5.92 µg/mL). Abutilins C can serve dual inhibitors as antioxidant agent and to treat α-glucosidase associated diseases. Phytochemicals geometries i.e ground state were optimized by density functional theory (DFT) B3LYP/TZ2P to understand the electronic properties of the studied compounds. The ground state geometries of abutilin_C, abutilin_D and reference compounds were optimized by DFT then various electronic properties were explored. Moreover, we have also investigated the global molecular descriptors, molecular electrostatic potential, Hirshfeld analysis and molecular docking by quantum chemical calculations.