A new hemiacetal chromone racemate and α-glucosidase inhibitors from Ficus tikoua Bur

From the petroleum ether and ethyl acetate portions of the 95% ethanol extract of Ficus tikoua Bur., a new hemiacetal chromone racemate, named (±)-ficunomone (1), together with twenty-two known flavonoids (2-23) were isolated. The new structure was elucidated by NMR, HRESIMS, and X-ray single-crystal diffraction analysis, and the known structures were determined by comparison of spectroscopic data with those reported from literatures. All the compounds were assayed for their inhibitory activities against yeast α-glucosidase, seven flavonoids could inhibit α-glucosidase, among which compounds 22 and 23 exhibited the highest inhibitory activity, with IC₅₀ values at 5.12 ± 0.10 and 3.43 ± 0.15 μM respectively. Preliminary structure and relationship activity of all the compounds was analysed. Kinetic analysis of compounds 22 and 23 indicated that they are both uncompetitive inhibitors. Molecular docking studies revealed that they bound to amino acid residues of the α-glucosidase activity pocket.