Antimicrobial Activities and Phytochemical Screening of Some Invasive Alien Species of Nepal

Abstract

In the present study, the antimicrobial activities and phytochemical screening of three Invasive Alien Species were studied. The crude extracts of the alien species (Ageratina adenophora, Ipomoea carnea ssp. fistulosa and Xanthium strumarium) were prepared by using distilled water and methanol as solvents. The antimicrobial activity against six pathogenic bacteria, three gram negative: Klebsiella pneumoniae (ATCC 15380), Proteus mirabilis (ATCC 49132), Escherichia coli (ATCC 25922) and three gram positive: Bacillus subtilis (ATCC 6633), Enterococcus faecalis (ATCC 29212), Staphylococcus aureus (ATCC 25932) and five phytopathogenic fungi: Alternaria brassicae, Botrytis cinerea, Fusarium oxysporum, Phytophthora capsici and Sclerotium rolfsii of different concentrations (50 mg/ml, 100 mg/ml, 150 mg/ml, 200 mg/ml, 250 mg/ml) of selected plant extracts was studied. The highest (16.48%) crude extract was obtained in A. adenophora in distilled water and the lowest (6.2%) in methanolic extract of X. strumarium. The phytochemical screening depicted the presence of terpenoids, saponins, cardiac glycosides, flavonoids, reducing compounds, tannins, phlabotannins and alkaloids. Seven replicates were used for each tested microbes.

The antibacterial activity of extracts was determined by disc diffusion method and zone of inhibition (ZOI) was measured. Gram negative bacteria was found more resistant than gram positive bacteria. The most susceptible bacteria was S. aureus while the most resistant bacteria was E. coli. Methanolic extract was found more effective than distilled water.

The antifungal activity of extracts was determined by poisoned food technique and linear mycelium growth reduction (LMGR) percentage was calculated. The distilled water extracts inhibited the growth of fungal mycelium while methanolic extracts completely inhibited (100%) the growth of some selected fungi at higher concentrations. Fusarium oxysporum was the most susceptible fungus while A. brassicae and B. cinerea were the most resistant fungi. Between bacteria and fungi, bacteria was found more susceptible than fungi against both distilled water and methanol extracts of selected IAS. Key words: IAS, Antimicrobial property, ZOI, LMGR, Phytochemical Screening.