Dipeptidyl peptidase-4 inhibitory activity of indonesian anti-diabetic herbs: Carica papaya, Tithonia diversifolia, Urena lobata

Incretin hormone is a new therapy for type 2 diabetes related to their activity for regulating blood glucose level. Even though, this hormone is destroyed by Dipeptidyl Peptidase-4 (DPP-4) become in-active form. DPP-4 inhibition will be beneficial for type 2 diabetes therapy. Empirically, some of local herbs are used by Indonesian people to cure diabetes, however, activity on DPP-4 inhibitory has not been examined. The objective of study to examine Indonesian anti-diabetic herbs Urena lobata (U. lobata), Tithonia diversifolia (T. diversifolia) and Carica papaya (C. papaya) through inhibition of DPP-4. The in vitro study use vildagliptin and Gly-pro-p-nitroanilide (GPPN) as a reference standard and substrate respectively. C. papaya leaf extract, T. diversifolia and U. lobata were prepared both of by decoction methods and digeration with ethanol. The data were expressed as mean ± SD and the Inhibitory Concentration (IC)-50 value was calculated by non-linear regression curve fit. U.lobata leaves in ethanolic extract had more inhibitory potency on DPP-4 compare to T. diversifolia and C. papaya with an IC-50 value of 1.65mg/mL, 26.12mg/mL and 34.02mg/mL respectively. Meanwhile, on aqueous extract from U.lobata, C. papaya and T. diversifolia with IC-50 value 6.49mg/mL, 14.99mg/mL and 15.39 mg/mL respectively. U.lobata leaf extract most strongly to inhibit DPP-4 activity regulated by active compounds in its extract like stigmasterol, β-sitosterol and mangiferin. Ethanolic extract of U.lobata leaves more potent than aqueous extract to inhibit DPP-4 activity and both of them showed the most inhibitory activity on DPP-4 among other.