Abstract
Objective: The aim of this study is to evaluate the antioxidant potential, determination of total phenolic and flavonoid content in nine selected medicinal plants Spondias pinnata, Melia azedarach, Ageratina adenophora, Urtica dioica, Curcuma longa, Bauhinia variegata, Elaeocarpus angustifolius Blume, Achyranthes aspera, and Psidium guajava from Kavre district of Nepal using in vitro studies.
 Methods: Methanolic plant extracts were prepared by cold percolation method. The methanol extract of nine medicinal plants collected from Kavre district of Nepal, was screened for assessing bioactive phytoconstituents followed by antioxidant property, total phenolic, and flavonoid content. Different plants collected were powdered and extracted with methanol, concentrated by a rotatory evaporator and analyzed for the presence of phytochemicals. The antioxidant potential of the plant extracts was evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay.
 Results: The phytochemical analysis of methanolic extracts of all nine medicinal plants displayed the presence of various secondary metabolites such as alkaloids, flavonoids, polyphenols, saponins, and quinones. The extract of S. pinnata showed the highest percentage of radical scavenging activity up to 87.94±1.88 with 50% inhibitory concentration (IC50) 17.51±1.27 μg/mL, followed by B. variegata, 80.63±1.06 with IC50 value 26.55±2.61 μg/mL. The standard, ascorbic acid has IC50 value of 20.13±1.17 μg/mL. Further, the ethyl acetate fraction of S. pinnata showed the maximum percentage of radical scavenging (85.92±1.37) with IC50 value of 46.95±1.17 μg/mL. Moreover, S. pinnata displayed the highest total phenolic content (TPC) 48.26±1.23 mg GAE/g (milligram gallic acid equivalent per gram) extract while the highest flavonoid content was displayed by Melia azedarach 41.07±1.53 mg QE/g (milligram quercetin equivalent per gram) extract measured by the Folin–Ciocalteu reagent method and aluminum chloride colorimetric method.
 Conclusions: The preliminary results of this study have put forward the extract of S. pinnata showed the highest percentage of radical scavenging activity and S. pinnata displayed the highest TPC while the highest flavonoid content was displayed by Melia azedarach methanolic extracts although the further studies are needed to assess its mechanism of action.
Highlights
Due to its greatly varied geographical and climatic conditions of Nepal, there is huge biodiversity of plants with medicinal and aromatic values
The Total flavonoid content (TFC) of different selected medicinal plant extracts was found and the results revealed that the TFC varied from 2.52±0.97 mg quercetin equivalent (QE)/g in Achyranthes aspera to 41.07±1.53 mg QE/g in Melia azedarach
The DPPH radical scavenging activities and subsequently the IC50 values of methanolic extracts of the selected plants showed a varied degree of antioxidant property; of which, S. pinnata showed appreciable percent scavenging followed by B. variegata
Summary
Due to its greatly varied geographical and climatic conditions of Nepal, there is huge biodiversity of plants with medicinal and aromatic values. Kavre district of Nepal is rich in biodiversity due to climatic variation and possesses varied medicinal plants. Medicinal plants are potent sources of medicine to treat various diseases. The people (approximately 80%) living in rural areas of underdeveloped countries still depend on medicinal plants for their basic health care [1]. Synthetic drugs are effective to cure various diseases, but in the long run, they show harmful side effects and they are expensive too. The drug development from the natural product is promising as plants show different bioactivity to cure ailments due to the presence of bioactive compounds
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