Ethnopharmacological evaluation of selected east kalimantan flora for diabetes therapy: The isolation of lupane triterpenoids as α-glucosidase inhibitors from ceriops tagal (perr) c.b.robb

Abstract

The current study evaluated the antidiabetic activity of particular East Kalimantan plants that have long been used by Dayak people for diabetes therapy and identified the active compounds in these plants. However, the antidiabetic activity of the indigenous plants has not been systematically investigated. Phytochemical analysis of six selected East Kalimantan plant extracts was conducted to investigate their: (1) antidiabetic activities (via α-glucosidase inhibition bioassays), (2) DPPH radical scavenging activities, and (3) total antioxidant capacities. Additionally, the mechanisms underlying the inhibitory effects of the isolated compounds were determined by Lineweaver-Burk plots. The extracts showed α-glucosidase inhibitory activities with IC50 values ranging from 0.07 to 8.09 mg/mL. Ceriops tagal exhibited the highest DPPH radical scavenging activity (IC50 26.24 µg/mL), as well as the highest total antioxidant capacity (215.16 ± 0.02 mgGAE/g). Bioassay-guided isolation of C. tagal, which was the plant with the most significant apparent potential, yielded three triterpenoids: lupeol (1), betulone (2), and betulin (3). Of the isolated compounds, 3 exhibited the highest inhibition with IC50 value of 18.87 μM. Furthermore, all isolated triterpenoids showed noncompetitive inhibition action. The systematic screening approaches were successfully applied to identify antidiabetic agents from East Kalimantan plants.