Estimation of phytochemicals, antioxidant, antidiabetic and brine shrimp lethality activities of some medicinal plants growing in Nepal

Background: Extreme production of free radicals in the human body causes direct damage to biological molecules that leads to the different types of diseases. The natural or synthetic antioxidants inhibit directly the production or restrict propagation or nullify the free radicals produced in the human body to protect the immune system. Objective: This study aims to quantify the total phenolic and flavonoid content, antioxidant and antidiabetic activities and toxicity test for the methanol extracts of aerial parts of traditionally used medicinal plants like Ageratina adenophora (Spreng.) R.M.King & H.Rob., Cupressus sempervirens L. and Lantana camara L. Methods: The total phenolic content (TPC) was estimated by Folin-Ciocalteu reagent method and the total flavonoid content (TFC) by aluminum chloride assay. The α-amylase inhibition activity was performed to evaluate the antidiabetic activities of plant extracts. Results: Lantana camara showed the highest phenol content (10.20 ± 0.343 mg gallic acid equivalent /g extract) and flavonoid content (1.87 ± 0.160 mg quercetin equivalent /g extract) among the three plant samples, respectively. The methanol extracts of Lantana camara showed the strongest DPPH radical scavenging activity with IC50 of 106.18 ± 11.390 µg/ml. In addition, Ageratina adenophora methanol extract was found to inhibit α-amylase activity with IC50 value of 1.84 ± 0.007 mg/ml. The methanol extract of Ageratina adenophora was found to be toxic against brine shrimp with median lethal concentration (LC50) value of 833.68 µg/ml. Conclusion: This research shows that the traditionally used medicinal plants are the rich and potent sources of natural antioxidant and antidiabetic compounds which may be the potent natural drug candidates in the future drug discovery process.