Efficacy of ionic liquid [MIM]BR-based MAE on resveratrol and phenolic compounds extraction from gnetum gnemon seeds and their DPP-4 inhibitory activity

Objective: This study aimed to determine the inhibitory activity of 1-butyl-3-methylimidazolium bromide ([bmim]Br) extracts of melinjo seeds (Gnetum gnemon) on dipeptidyl peptidase-4 (DPP-4). Methods: Melinjo seeds were extracted by a [bmim]Br microwave-assisted method using various extraction parameters and the inhibitory activity of DPP-4 of all extracts was determined in 96-well microplates using Cayman inhibitor screening assay. Determination of trans-resveratrol content was conducted using a reverse-phase high-performance liquid chromatography method. The total phenolic content was determined using a 96-well microplate reader. Data analysis for the determination of the optimal extraction conditions was developed by response surface methodology. Results: The extract obtained from the third run showed the highest inhibition (28.73%) against DPP-4 activity with the total phenolic content of 1.96 mg gallic acid equivalent/g the seed powder. Conclusion: The analytical results revealed the following optimal conditions: Solvent concentration 1.5 M, liquid-solid ratio 23:1, and extraction time 15 min.