Background: Nature provides a rich source of antidiabetic medicines. More than 1.200 plants have been reported to have anti-diabetic activities and more than half of the drugs on the market come from natural products. Therefore, research for developing new antidiabetic drugs from natural sources is necessary to properly evaluate various mechanism of action, efficacy and safety at toxicological, physiological, pharmacological and molecular levels before these drugs applied in treatment of diabetes. This study aims to examine and determine the highest activity of 10 ethanol extracts from Indonesian plants selected for in vitro inhibitory activity of dipeptidyl peptidase - IV (DPP-IV). Materials and Methods: This research studied DPP-IV inhibitory mechanism from 10 plant extract, namely Caesalpinia sappan, Cinchona officinalis, Elephantopus scaber, Foeniculum vulgare, Morus nigra, Muntingia calabura, Phyllanthus niruri, Psidium guajava, Rheum palmatum and Vernonia amygdalina using the spectrophotometric method and Sitagliptin as a positive control. The effectiveness of inhibition was assessed by percent inhibition. Tannin removal test was performed to exclude false-positive results. Results: The ethanolic extract of Caesalpinia sappan exhibited DPP-IV inhibitory activity greater than 80%, which was not markedly different from that of Sitagliptin at 85%. Brazilin, an active compound from Caesalpinia sappan gave the inhibition at greater than 78%. Tannin removal test for Caesalpinia sappan gave the inhibition at 74.16%. The High Performance Liquid Chromatography (HPLC) analysis result displayed that brazilin content on Caesalpinia sappan extract was 91.94%. Conclusion: Based on these results, Caesalpinia sappan ethanol extract has a potential effect as a better antidiabetic agent than other extracts used in this study.
Key words: Antidiabetic, DPP-IV, Caesalpinia sappan, Inhibitory activity.