Abstract

Recently, attention has focused on phytochemicals as new sources of natural antioxidants.Therefore, the methanolic crude extracts of 24 commonly used medicinal plants fromJhapa and Illam District, Nepal, were screened for total phenols, flavonoids, and free radical scavenging activity. Free radical scavenging activity was evaluated using 1,1-diphenyl-2-picryl-hydrazyl (DPPH). Significant differences in DPPH scavenging activity were found between the species investigated, ranging from 14.67 ± 1.00% to 92.33 ± 1.53%. The highest radical scavenging activity was observed in Artemisia vulgaris (92.33 ± 1.53% inhibition), followed by Ficus lacor (92.00 ± 1.73%) and Mallotus philippensis (91.33 ± 1.53%). The total phenol content of the investigated species ranged from 28.87 ± 2.36 to 321.23 ± 1.06 mg GAE/g extract, while flavonoid content ranged from 13.53 ± 0.85 to 100.33 ± 1.53 mg QE/g extract. A weak linear correlation between total phenolic or flavonoid content and antioxidant activity was found (correlation coefficient, R² = 0.3004, R² = 0.4294, respectively), indicating that the major antioxidant components might not be phenolics. In particular, A. vulgaris, F. lacor, M. philippensis, Trachyspermum ammi, and Amomum subulatum showed strong activity against DPPH, and thus could be used as natural antioxidants in the food and/or pharmaceutical industry.

Key words: Phenolic content, flavonoids, medicinal plants, antioxidant activity, methanolic extraction.