Identification of Alpha-glucoside Inhibitors and Antioxidants in Zinger officinale Rhizome using LC-MS Based Metabolomics and Molecular Docking

Abstract

Zingiber officinale (ginger) rhizome has widely used as a spice and folk medicine for anti-diabetic. Though some researchers have investigated the pharmacological aspect of the plant's anti-diabetic properties, there is a need for metabolite profiling to reveal the bioactive chemicals responsible for the plant's anti-diabetic effects via inhibition of ?-glucosidase. The aims of the present study are to evaluate the ?-glucosidase inhibitory activity of the ginger ethanolic extract, to identify the putative ?-glucosidase inhibitors from the rhizome using LC-MS based metabolomics, and to analyse the molecular interaction of these inhibitors to the enzyme receptor via in silico molecular docking analysis. The ginger rhizome was extracted using solvents with different concentrations of methanol in water (100, 75, 50, 25, and 0%, v/v). The extracts were tested via in vitro ?-glucosidase inhibitory assay and analysed using LCMS-QTOF. The data obtained were subjected to multivariate data analysis to pinpoint the putative ?-glucosidase inhibitors. The molecular interaction between the putative ?-glucosidase inhibitors and the enzyme was investigated using in silico molecular docking. The ginger methanol extract exhibited the highest ?-glucosidase inhibitory (AGI) activity (IC50= 185.2 ?g/mL) compared to the other extracts. This extract also showed antioxidant activities with DPPH-IC50 and FRAP value of 125.0 ?g/mL and 16.95 mmol TE/mgDW, respectively. The LCMS-based metabolomics revealed several ?-glucosidase inhibitors in the ginger rhizome, namely 7-methoxycoumarin, supinine and 12- hydroxycorynoline. Although the existence of these compounds has been reported in other plants, the presence of these compounds in ginger is being reported for the first time in this study. The activity of these compounds was supported by computational study using in silico molecular docking. These compounds displayed binding energy values less than the control ligand (< -6.0 kcal/mol) indicating their strong affinity to the enzyme. Methoxycoumarine and supine formed interactions with ASP 352 and ARG 422 through ? -anion interaction hydrogen bond, respectively. Similarly, supinine interacted with ARG 442 through a hydrogen bond. These interactions took place at the active site of an enzyme while, 12-hydrocoryline interacted with an allosteric binding site of the enzyme. This study highlights the potential of the ginger rhizome as antidiabetic agent via ?-glucosidase inhibitory activity and anti-oxidant mechanisms, which is beneficial in the development of future anti-diabetic nutraceuticals.