Multiple spectroscopic fingerprinting platforms for rapid characterization of α-glucosidase inhibitors and antioxidants from some commonly consumed Indonesian vegetables and spices

Abstract

Indonesia has one of the most significant biodiversity in the world. Many edible plants have served as the sources of bioactive compounds such as α-glucosidase inhibitors and antioxidants, including several vegetables and spices. However, the potential of active biomolecules present in these food crops have not been fully explored. This study is aimed at screening α-glucosidase inhibitory and antioxidant activities in ten vegetables and spices commonly consumed in Indonesia. Phytochemicals of the most potent samples were characterized using different spectroscopic fingerprinting tools. The samples consisted of Polyscias fruticosum, Anacardium occidentale, Centella asiatica, Moringa oleifera, Arcypteris irregularis, Carica papaya, Kaempferia galanga, Curcuma mangga, Allium schoenoprasum, and Allium fistulosum. The results showed that the leaves of Anacardium occidentale had the best α-glucosidase inhibitor and antioxidant activities (IC50 108.04 and 114.78 μg mL−1, respectively), followed by Arcypteris irregularis (IC50 145.54 ± 1.79 and 179 ± 5.81, respectively) and Polyscias fruticosum (IC50 107.79 ± 0.6 and 137.59 ± 2.67 μg mL−1, respectively) The total phenolic content of the three samples were in the same pattern as the α-glucosidase inhibitor and antioxidant activities. However, the 1H NMR (Nuclear Magnetic Resonance) profile of Arcypteris irregularis contained fewer signals at typical phenolics chemical shifts. Characterization of functional groups associated with the activities was conducted using FTIR (Fourier Transform Infrared) metabolomics of A. occidentale’s n-hexane, chloroform, ethyl acetate, and water fractions. Functional groups that positively correlated with A. occidentale’s bioactivities mostly originated from aromatic frequencies. This was in line with LC–MS (Liquid Chromatography-Mass Spectrometry) analysis results, which revealed that the most active fractions (ethyl acetate fraction) contained quercetin, quercetin-3-galactoside, kaempferol-3-O-glucoside, kaempferol, rhamnetin, and agathisflavone. These results suggested that the under-utilized A. occidentale leaves can be used to develop a functional food with antidiabetic and antioxidant activities.