Molecular docking and inhibition studies of α-amylase activity by labdane diterpenes from Alpinia nigra seeds

Wide varieties of synthetic drugs are available for combating type 2 diabetes but are not free of associated side effects. Commercially available antidiabetic drugs are known to be potent inhibitors of α-amylase which reduce postprandial hyperglycaemia. Here, we have investigated Alpinia nigra seed extracts and the isolated two labdane diterpenes ( I and II ) for the α-amylase inhibitory activity. These labdane type diterpenes showed more promising inhibitory effects (IC 50 value 24.3 ± 2.05 and 15.167 ± 0.52 μM for compound I and II , respectively) against α-amylase than the standard inhibitor, acarbose. For both compounds, the mode of enzymatic inhibition was found to be non-competitive with K i 13.303 ± 0.065 and 12.19 ± 0.099 μM, respectively. Molecular docking studies revealed that both I and II bind the human pancreatic α-amylase in the active site cleft similar to the acarbose. Among all the compounds under investigation, acarbose and compound II were found to have the highest MolDock and re-rank score. Further molecular dynamic simulation studies also supports the docking results obtained for both I and II . This is the first report on α-amylase inhibitory effect of the two labdane diterpenes with their potential candidature as future antidiabetic drugs of herbal origin.