α-Glucosidase Inhibition and Molecular Docking Studies of Natural Brominated Metabolites from Marine Macro Brown Alga Dictyopteris hoytii

Bioassay guided isolation of the methanolic extract of marine macro brown alga Dictyopteris hoytii afforded one new metabolite (ethyl methyl 2-bromobenzene 1,4-dioate, 1), one new natural metabolite (diethyl-2-bromobenzene 1,4-dioate, 2) along with six known metabolites (3-8) reported for the first time from this source. The structure elucidation of all these compounds was achieved by extensive spectroscopic techniques including 1D (H-1 and C-13) and 2D (NOESY, COSY, HMBC and HSQC) NMR and mass spectrometry and comparison of the spectral data of known compounds with those reported in literature. The in vitro alpha-glucosidase inhibition studies confirmed compound 7 to be the most active against alpha-glucosidase enzyme with IC50 value of 30.5 +/- 0.41 mu M. Compounds 2 and 3 demonstrated good inhibition with IC50 values of 234.2 +/- 4.18 and 289.4 +/- 4.91 mu M, respectively, while compounds 1, 5, and 6 showed moderate to low inhibition. Furthermore, the molecular docking studies of the active compounds were performed to examine their mode of inhibition in the binding site of the alpha-glucosidase enzyme.