Apigenin isolated from A-americana encodes Human and Aspergillus oryzae S2 α-amylase inhibitions: credible approach for antifungal and antidiabetic therapies

Agave americana extract was analyzed by reverse phase HPLC for characterization. Among phenolic compounds identified, apigenin was observed to be present. The finding showed an inhibitory effect of apigenin towards Human and Aspergillus oryzae S2 alpha-amylases. Apigenin inhibition towards Human and A. oryzae alpha-amylase activities was observed to be competitive. IC50 and % inhibition of apigenin for A. oryzae alpha-amylase were 3.98 and 1.65 fold higher than for Human alpha-amylase. The inhibition of the described biocatalyst activity was significantly lowered when apigenin was pre-incubated with starch. In addition to the catalytic residues, 44 amino acid residues were involved on A. oryzae alpha-amylase-apigenin interactions while only 11 amino acid residues were exposed for Human alpha-amylase-apigenin complex. The binding site of apigenin showed 76 polar contacts for A. oryzae S2 alpha-amylase against 44 interactions for Human alpha-amylase. The docking studies confirmed the mode of action of apigenin and strongly suggested a higher inhibitory activity towards fungal amylase which was experimentally exhibited. These findings provided a rational reason to establish apigenin capability as a therapeutic target for postprandial hyperglycaemia modulation and antifungal therapy.