Phytochemical analysis, biological activities, and GC profiling of extracts of some medicinal plant growing in Nepal

Abstract

The present study was aimed to determine the antioxidant, α amylase inhibition, and antibacterial activities on ten traditionally used medicinal plant extracts, namely Cyperus rotundus, Citrus medica, Gaultheria fragrantissima, Jasminum humile, Osyris wightiana, Buddleja asiatica, Berberis aristata, Robus ellipticus, Schima wallichii, and Smilax ovalifolia growing in Nepal. The bioactive fraction of J. humile was subjected for GC analysis. The free radical scavenging properties of plant extracts were assessed using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and antibacterial activity was performed by the well diffusion method. The antidiabetic activity was assessed α amylase inhibition assay. The chemical compounds were isolated from the active plant fraction by silica column chromatography, and the collected fractions were analyzed by GC and FTIR. The phytochemical analysis showed that plant extracts were rich sources of secondary metabolites. The in vitro antioxidant activity showed IC₅₀ ranging from 30.57±0.02 to 155.65±0.10 µg/mL. The promising antioxidant activity was demonstrated by S. wallichii of IC₅₀ 30.57±0.02 µg/mL and J. humile 35.28±0.54 µg/mL, respectively whereas, the S. ovalifolia, exhibited the moderate antioxidant activity of IC₅₀ 155.65±0.10 µg/mL. The J. humile showed significant antidiabetic activity of IC₅₀ 59.4±23.47 µg/mL. The antidiabetic activities exhibited ranged from IC₅₀ of 77.29±2.05 (S. wallichii to 608.28±71.50 µg/mL (C. rotundus). The R. ellipticus showed maximum ZOI (22 mm) against the Staphylococcus aureus (ATCC 25923), whereas J. humile (20 mm), O. wightiana (18 mm), and G. fragrantissima (16 mm) showed moderate antibacterial activity against the S. aureus. The C. rotundus, J. humile, S. ovalifolia, O. wightiana, and B. asiatica showed promising antibacterial activity against E. coli (ATCC 25922) with ZOI 15, 17, 14, 17, and 18 mm respectively. These findings provide partial scientific support for traditional uses of these medicinal plants against diabetes and infectious diseases. Therefore, the J. humile could be a promising source of natural antidiabetic and antioxidant compounds that may be drug candidates for future drug development. To the best of our knowledge, this work is the first attempt to perform all these biological activities and phytochemical analyses growing in the particular region of Nepal.