Vol. 13 | No. 3 |1727-1734| July - September | 2020 ISSN: 0974-1496 | e-ISSN: 0976-0083 | CODEN: RJCABP http://www.rasayanjournal.com http://www.rasayanjournal.co.in Rasayan J. Chem., 13(3), 1727-1734(2020) http://dx.doi.org/10.31788/RJC.2020.1335559 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 R. Ramadhan 1,2,* , P. Phuwapraisirisan 3 , I.W. Kusuma 4 and R. Amirta 4 1 Department of Chemistry, Faculty of Science and Technology/Airlangga University, Surabaya-60115, (East Jawa) Indonesia 2 Division of Exploration and Synthesis of Bioactive Compounds, Research Center for Bio- Molecule Engineering/Airlangga University, Surabaya-60115, (East Jawa) Indonesia 3 Center of Excellence in Natural Products Chemistry, Faculty of Science/Chulalongkorn University, Bangkok-10330, (Bangkok) Thailand 4 Forest Products Chemistry and Renewable Energy Laboratory, Faculty of Forestry/Mulawarman University, Samarinda-75242, (East Kalimantan) Indonesia *E-mail: rico.ramadhan@fst.unair.ac.id 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. Keywords: Antidiabetes, Antioxidant, Ceriops tagal, Ethnopharmacology, East Kalimantan. © RASĀYAN. All rights reserved INTRODUCTION Diabetes mellitus (DM) is a chronic and complex disorder of metabolic ailment caused by hyperglycemia, subsequent from lacking pancreatic insulin secretion, with the change of insulin action that can develop complications in diabetes. 1-3 The onset of diabetes mellitus is attributed to several factors including persistent hyperglycemia toxicity and oxidative stress. 4 Recently, studies have shown that oxidative stress is involved in the development of diabetic complications by impairing the oxidation-reduction a system, which leads to β-cell failure and insulin resistance. 5 Current clinical therapies are based on the control of postprandial hyperglycemia by the α-glucosidase as a target. Among them, the most effective pharmacologicalα-glucosidase inhibitors are acarbose, miglitol and voglibose. 6 However, consumption of those synthetic drugs should be limited because potentially produce various side effects such as