Antibacterial Activity and Phytochemical Screening of Some Medicinal Plants of Nepal

Abstract

Eighteen different medicinal plants which were being used to treat the bacterial diseases in Nepal were selected. The medicinal plants were extracted in methanol by soaking method. The Drymaria cordata gave the highest yield (20%) whereas Urtica dioica gave lowest yield (4%). The methanol extract of these plants were evaluated for antibacterial activity against medically important bacteria viz. Bacillus subtilis, Pseudomonas aeruginosa, Salmonella typhi, Proteus vulgaris, Escherichia coli, and Staphylococcus aureus. The in vitro antibacterial activity was performed by agar disc diffusion method. Among 18 medicinal plants tested, in the present study, all plants showed activity against at least two bacteria. Phyllanthus amarus and Rhus javanica inhibited all the tested bacteria. Similarly, Drymaria cordata was effective against 83% of tested bacteria. Nine plants (Bauhinia purpurea, Ageratum conyzoides, Urtica dioica, Lantana camara, Cinnamomum tamala, Melia azedarach, Vitex negundo, Oxalis corniculata, and Zizyphus mauritiana) inhibited the growth of 67% and five plants (Euphorbia hirta, Taraxacum officinale, Achyranthes bidentata, Mimosa pudica, and Cissampelos pareira) were effective against only 50% of screened bacteria and remaining one plant Ficus religiosa inhibited growth of 33% of the screened bacteria. The most susceptible bacteria were Staphylococcus aureus whose growth was inhibited by 17 out of 18 plants screened whereas Escherichia coli were found to be the most resistant bacteria being susceptible to only five plants. The gram-positive bacteria were found to be more susceptible as compared to gram-negative bacteria. Phytochemical screening was also performed on all these plants on aqueous and alcoholic extract by their color reaction with different reagents and chemicals to detect the presence of alkaloids, glycosides, saponins, terpenoids, and tannins. Most of the plants contain these secondary metabolites but on varying concentration. Among the screened plants, 67% of plants contain alkaloids, 78% plants found to contain glycosides, saponins and terpenoids each and 72% plants showed the presence of tannins. The medicinal plants which were used against bacterial disease were found to have antibacterial principles and were found to be rich in different phytochemicals.