LC-QTOF-MS based metabolite profiling and evaluation of α-glucosidase inhibitory kinetics of Coccinia grandis fruit

Coccinia grandis (C. grandis) is an important food crop of Cucurbitaceae family, widely used as culinary purpose in India. It is reported to possess hypoglycemic, hypolipidemic, and antioxidant activities. The current study was aimed to explore the inhibition kinetics as well as major constituents of active fraction of C. grandis against α-glucosidase. The kinetic study was performed through spectrophotometric assay, with p-nitrophenyl-α-D-glucopyranoside as a substrate with varying concentration. In vitro antioxidant study was performed by DPPH assay. In addition, UPLC-QTOF-MS analysis was carried out for metabolite profiling of bioactive fraction of C. grandis. The results showed that the difference between the α-glucosidase inhibitory activity of ethyl acetate fraction of C. grandis (EFCG) (IC₅₀ 2.43 ± 0.27 mg/mL), and standard inhibitor, acarbose (2.08 ± 0.19 mg/mL) was not statistically significant at a p-value of 0.05. The enzyme kinetics confirmed the inhibition mode in a mixed manner. The EFCG also showed the highest antioxidant activity (101.74 ± 1.95 μg/mL) among all the fractions. A significant correlation between antioxidant and α-glucosidase inhibitory activity of EFCG was observed. LC-QTOF-MS study of the EFCG putatively identified 35 metabolites, which may be responsible for its antioxidant and α-glucosidase inhibitory properties. Thus, C. grandis fruits can serve as a functional food to address the diabetes-related disorders associated with α-glucosidase.

Keywords: Coccinia grandis; inhibition kinetics; metabolites, LC-QTOF-MS, phenolics; α-glucosidase.