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Indian Journal of Pharmacology, Vol. 38, No. 2, March-April, 2006, pp. 142-144 Research Letter Activity of some medicinal plants against certain pathogenic bacterial strains Nair R, Chanda S Phytochemical, Pharmacological and Microbiological Laboratory, Department of Biosciences, Saurashtra University, Rajkot-360005, Gujarat Code Number: ph06037 Medicinal plants are an important therapeutic aid for various ailments. Scientific experiments on the antimicrobial properties of plant components were first documented in the late 19th century.[1] In India, from ancient times, different parts of medicinal plants have been used to cure specific ailments. Today, there is widespread interest in drugs derived from plants. This interest primarily stems from the belief that green medicine is safe and dependable, compared with costly synthetic drugs that have adverse effects. Natural antimicrobials can be derived from plants, animal tissues, or microorganisms.[2] The shortcomings of the drugs available today, propel the discovery of new pharmacotherapeutic agents in medicinal plants.[3] To determine the potential and promote the use of herbal medicine, it is essential to intensify the study of medicinal plants that find place in folklore.[4],[5] In this study, some selected plants of Saurashtra region, India, were screened for potential antibacterial activity. A total of 20 plants were screened. [Table - 1] Different parts of the plants were collected, air dried, and powdered in a homogeniser, and 10 g of each plant was used for aqueous and ethanol extraction. The aqueous extraction was done in distilled water for 6 hours at slow heat. The extract was concentrated to 1/5th of the original volume for antimicrobial assay. For ethanol extraction, the sample was extracted in ethanol kept on a rotary shaker overnight. The filtrate was collected and centrifuged at 5000 rpm. The extract was concentrated to 1/5th of the original volume and used for antimicrobial assay. Seven Gram negative strains, Pseudomonas aeruginosa ATCC27853, Pseudomonas testosteroni NCIM5098, Proteus mirabilis NCIM2241, Proteus vulgaris NCTC8313, Enterobacter aerogenes ATCC10240, Escherichia coli ATCC25922, and Citrobacter freundii ATCC10787 and five Gram positive strains Staphylococcus epidermidis ATCC12228, Bacillus cereus ATCC11778, Streptococcus fecalis ATCC29212, Streptococcus cremoris NCIM2179, and Streptococcus agalactiae NCIM2401 were used in the investigation of antibacterial activity. All the bacterial strains were obtained from the National Chemical Laboratory (NCL), Pune, Maharashtra, India. The media employed were Mueller Hinton Agar No.2 (Himedia, India), Nutrient Broth (Himedia, India), MRS media (Himedia, India), and MRS broth (Himedia, India). Agar ditch diffusion method[6] and disc diffusion method[7] were used for the antibacterial assay. The test bacterial strains were maintained on agar slants at 4o C. The bacterial strains were recovered for testing by inoculating into nutrient broth (Himedia) as well as MRS broth (Himedia) on rotary shaker. For antibacterial evaluation, 100 µl of the inoculum size (1 X 10 8sub cells/ml) was taken. The plates were incubated at 37°C for 24 h. The results were obtained by measuring the zone diameter. Maximum antibacterial activity was shown by the aqueous extracts of P. hysterophorus . None of the plant extracts could inhibit S. agalactiae, E. coli, C. freundii, and P. vulgaris. The aqueous extract of P. hysterophorus inhibited the growth of seven strains among the 12 bacterial strains studied. It showed maximum activity against P. aerugionsa. The aqueous extracts of F. benghalensis and A. graveolens could not inhibit any of the bacterial strains, while the aqueous extracts B. diffusa, A. racemosus, F. religiosa, C. benghalensis , O. sanctum and Z. nummularia showed minimum antibacterial activity. H. sabdariffa showed maximum activity against S. fecalis. The antibacterial activity of ethanol extracts of various plants screened are shown in [Table - 2]. The ethanol extracts of B. diffusa, A. squamosa, H. sabdariffa , and A. racemosus showed the least antibacterial activity, while E. officinalis, C. wightii, F. religiosa, P. hysterophorus, F. benghalensis, F. tesila, F. racemosa, D. indica, C. papaya, O. sanctum, A. graveolens, P. granatum, and Z. nummularia showed maximum antibacterial activity. The ethanol extracts of P. hysterophorus, F. tesila, D. indica, and Z. nummularia inhibited the growth of 9 strains. P. hysterophorus showed maximum activity against B. cereus . F. tesila was highly active against S. agalactiae , while D. indica and Z. nummularia were highly active against S. agalactiae and E. aereogenes, respectively. These plant extracts were also compared with standard antibiotics, piperacillin and gentamicin. Aqueous extracts showed less activity than ethanol extracts possibly because i) the same active substances were present in water extracts, but in low concentrations ii) active substances were soluble in organic solvents and, therefore, not present in water extracts as also suggested by de Boer et al [8].The antibacterial action of the extracts is more pronounced on Gram positive than on Gram negative bacteria, and these findings correlate to the observations of previous screenings[5],[9] of medicinal plants for antibacterial activity. From the above results, it can be concluded that the plant B. diffusa did not exhibit any antibacterial property and P. vulgaris, E. aerogenes, and E. coli were the most resistant bacterial strains investigated. Plant extracts have great potential as antimicrobial compounds, especially in the treatment of infectious diseases caused by resistant microorganisms. References
Copyright 2006 - Indian Journal of Pharmacology The following images related to this document are available:Photo images[ph06037t2.jpg] [ph06037t1.jpg] |
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