Inhibition of Dipeptidyl Peptidase 4 (DPP IV) Activity by Some Indonesia Edible Plants

Background: Some edible plants are promising to control blood sugar level. These plants contained phenolic substances that suggested to be able to inhibit dipeptidyl peptidase 4 (DPP IV). Objective: The objective of this study was to investigate the inhibitory effect of several selected Indonesia plants on inhibiting of DPP IV activity and to determine the total phenolic content of the most active extract. Methods: Twelve Indonesia edible plants were macerated using 80% ethanol at room temperature. DPP IV activity was evaluated by using glycyl-prolyl-7-amino-4-methyl coumarin (Gly-Pro-AMC) substrate and the inhibitory effect of extracts were determined based on the level of free AMC group by measuring its fluorescence on excitation wavelength 350-360 nm and an emission wavelength 450-465 nm using a microplate reader. Total phenolic contents of the active extracts were determined with Folin-Ciocalteu 1:4 on 765 nm using microplate reader. Total anthocyanins from extract were determined using the pH differential method. Results: Among the tested samples, the extract of Ipomoea batatas roots at a concentration of 10 μg/mL showed the highest inhibition, followed by Cajanus cajan leaves and Gnetum gnemon rind, with percentage inhibition of 28.8, 24.9 and 24.1, respectively. I. batatas extract have an IC₅₀ value of 65.53 μg/mL, while the IC₅₀ value of the positive control Sitagliptin 9.37 μg/mL. Total phenolic content from the extracts of I. batatas, C. cajan and G. gnemon rind extract were 279.3; 152.8; and 141.3 mg GAE/gram, respectively. Total anthocyanin from I. batatas extract was 462.14 mg cyanidin- 3-glucoside/L. Conclusion: The extract of I. batatas showed the highest inhibition on DPP IV among other plants investigated and showed high content of phenolic compound and anthocyanin that correlated with activity as inhibitor DPP IV.