Antioxidant and alpha amylase inhibitory activity of Nepalese medicinal plants from Gorkha district

The aim of this study is to evaluate the antioxidant activity, α-amylase inhibition activity, estimation of total phenolic and flavonoid content and the toxicity in ten medicinal plants Woodfordia fructicosa, Tectaria coadunate, Prunus cerasoides, Abrus precatorius, Eclipta prostrate, Poranopsis paniculata, Chenopodium album, Oroxylum indicum, Curcuma caesia, and Butea monosperma collected from Gorkha District of Nepal. Methanolic extracts of all the plants showed the presence of different phytoconstituents such as alkaloids, polyphenols, flavonoids, terpenoids, saponins, glycosides, and quinones. The highest radical scavenging was observed in methanol extract of P. cerasoides with IC50 = 7.54±0.223 µg/ml. The potency of the radical scavenging effect of P. cerasoides was about six times greater than standard ascorbic acid (39.85±0.025 µg/ml) taken. P. cerasoides showed high phenol content (805.48±0.024 mg GAE/g extract) whereas total flavonoid content varied from O. indicum (16.96±0.015 mg QE/g extract) to W. fructicosa (722.76±0.108 mg QE/g extract). The methanol extract of E. prostrate was found to be toxic against brine shrimp as shown in the LC50 value of 6.3 µg/ml. T. coadunate and A. precatorius showed effective results with an IC50 value of 80.89 and 70.29 µg/ml respectively in α-amylase inhibition test. This study provides some scientific support for traditional uses of plants for diabetes management and other ailments. Since extracts of W. fructicosa and P. cerasoides are rich sources of bioactive chemical constituents, further in-vitro and in-vivo bioactivity of these extracts need to be studied for their exact mechanism of action. Key words: Antioxidant, 1,1-diphenyl-2-picrylhydrazyl (DPPH), phenolic content, flavonoid content, inhibition.