Evaluation of Antibacterial Activity of some Medicinal plants Frequently used in Respiratory and Gastrointestinal Diseases in Nepal

Abstract

In this study, antibacterial activity of 16 different medicinal plants were tested against 14bacteria. Both, zone of inhibition (ZOI), and minimum bactericidal concentration (MBC)values were determined. Medicinal plants were selected on the basis of their common use among the differentethnic groups for common disorder. The selected plants wereAchyranthes bidentata,Acorus calamus, Azadirachta indica, Cumminum cyminum, Glycyrrhiza glabra,Jasminum humile, Justicia adhatoda, Juniper indica, Mentha piperita, Myrica esculenta,Ocimum sanctum, Piper nigrum, Spilanthes calava, Syzygium aromaticum,Trachysperum ammiandZanthoxylum armatum. For the chemical extraction plants weresubjected to soxhlet extraction with ethanol whileJ. indicaandM.piperita to steamdistillation. After removing the solvent under reduced pressure residues were suspendedseparately in water, DMSO, ethanol and methanol.Myrica esculentagave the highestyield of 46.64%, yield obtained with essential oil was lowest. The bacteria selected for the inhibition test wereBacillus subtilis, Staphylococcus aureus,Streptococcus pneumoniae, Streptococcus pyogens, E.coli, Enterobacter aerogenesKlebsiella pneumoniae. Proteus mirabilis, Proteus vulgaris, Pseudomonas aeruginosa,Salmonella paratyphi, Salmonella typhi, Salmonella typhimurium and Shigelladysentriae. Among 16 tested plants, 12 plants(75%) showed activity against at least six or moretest bacteria and 4 plants(25%) were active against 3 or less than 3 bacteria .Syzygiumaromaticum was the most active plant as it was effective for all the test bacteria.Acorus calamuswas the least effective against the test organisms. Gram positive organisms were more sensitive to medicinal plants extracts than Gramnegative bacteria. Staphylococcus aureus was most susceptible among the 14 testbacteria. It was inhibited by 13 out of 16 medicinal plants extracts tested.Salmonellatyphimuriumwas found to be the most resistant species, being susceptible to only 5 plantextracts. The largest zone of inhibition (30mm) was observed withM. piperita(essentialoil) against B.subtilis while lowest minimum bactericidal concentration (0.097mg/ml)was given by DMSO suspension ofSyzygium aromaticumagainstK. pneumoniae. Antibiotic sensitivity test showed that Ps. aeruginosa was resistant to Amikacin,Cortimoxazole, Ciprofloxacin, Tetracycline and Gentamicin, but inhibited by 10 plantextracts. Glycyrrhiza glabra(Jethi madhu) was subjected to solvent extraction using solvent ofincreasing polarity into 4 fractions viz., hexane, chloroform, n-butanol and D/W.Among these n-butanol fraction was active against seven test bacteria that showedenhanced spectrum activity againstE.coli, however, ethanolic extract didnot showedzone of inhibition. The result obtained in this study reveal the confirmation of theantibacterial potential of theplants investigated, and their usefulness in treatment ofrespiratory and gastrointestinaldisease.