Phytochemical Screening, Free-Radical Scavenging Activity, in vitro Alpha-Amylase Inhibitory Activity, and in vivo Hypoglycemic Activity Studies of Several Crude Drug Formulations Based on Selected Medicinal Plants of Nepal.

Diabetes mellitus (DM) is a chronic metabolic disorder leading toward elevation of the blood glucose level due to insulin insufficiency (Type I) or insulin resistance of responsible tissues (Type II). Aside from allopathic medicine, herbal therapy using crude and extracted forms is drawing the interest of many researchers for its hypoglycemic effect. Therefore, this study was designed by selecting eight local medicinal plants – Azadirachta indica, Gymnema Sylvestre, Swertia chiraita, Cinnamomum tamala, Psidium guajava, Aegle marmelos, Urtica dioica and Momordica charantia – which have a long history of being utilized for glucose-lowering property to provide the experimental and scientific evidence of their antidiabetic efficacy. Among the four formulations prepared, tetra-herbal formulations F3 and F4 were found to have the highest total phenolic content (TPC) of 223.38 ± 0.25 μg GAE/mg plant extract and 220.24 ± 0.89 μg GAE/mg plant extract, respectively. At the same time, the total flavonoid content (TFC) study also revealed that F3 and F4 have the highest TFC of 282.29 ± 0.54 and 255.24 ± 0.37 μg QE/mg extract, respectively. Furthermore, antioxidant activity study showed that F3 and F4 showed potent DPPH free-radical scavenging effect with IC₅₀ values of 12.22 and 15.24 μg/mL, respectively. Continuing the experiment, it was established that the results of quantitative phytochemical screening and antioxidant activity study coincide with the in vivo and in vitro antihyperglycemic activity assay. Formulation F3 showed the potent alpha-amylase inhibition with an IC₅₀ value of 43.75 mg/mL, and the in vivo glucose-lowering efficacy of F3 showed its ability of markedly reducing the blood glucose level up to 130.2 ± 2.03 mg/dL within 21 days. With these findings, the present study provides evidence-based experimental and scientific basis for using these selected medicinal plants as high hypoglycemic activity agents. [ABSTRACT FROM AUTHOR]