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Antibacterial Activity in the Leaves of Seven Bitter Medicinal Plants of Bangladesh

M T H Molla
Department of Applied Chemistry and Chemical Engineering, University of Rajshahi, Bangladesh.

M S Ahsan
Department of Applied Chemistry and Chemical Engineering, University of Rajshahi, Bangladesh.

M T Alam
Department of Applied Chemistry and Chemical Engineering, University of Rajshahi, Bangladesh.

M E Haque
Department of Applied Chemistry and Chemical Engineering, University of Rajshahi, Bangladesh.

Abstract/ Executive Summary:

Context: Development of resistance in human pathogens against conventional antibiotic necessitates searching indigenous medicinal plants having antibacterial property. Seven medicinal plants used actively in folklore, ayurvedic and traditional system of medicine were selected for the evaluation of their antimicrobial activity for this study. Objectives: Evaluation of the effectiveness of some medicinal plant extracts against four Gram-positive and five Gram-negative bacteria. Materials and Methods: The antibacterial activity of the crude ethanolic extracts obtained from the leaves of seven medicinal plants; viz., Andrographis paniculata, Catharanthus roseus, Adhatoda vasica, Vitex vegundo, Aloe vera, Flacortia ramontchi and Nyctanthes arbortristis were tested against nine bacteria at concentrations of 300-, 400- and 500 μg/ml. Standard antibiotic disc kanamycin (30μg/ml) was used for comparison. The minimum inhibitory concentration (MIC) of ethanolic extracts of the leaves of these medicinal plants were determined by testing the extracts on four Gram-positive and five Gram-negative bacteria by serial tube dilution method. Results: All the extracts have notable antimicrobial activities against the test organisms. The ethanolic extracts of the leaves showed the highest antimicrobial activities against Bacillus megaterium and Shigella dysenteriae for An. paniculata, Ad. vasica and Al. vera; Bacillus subtilis and Salmonella typhi for C. roseus and N. arbortristis; Staphylociccus aureus and Salmonella typhi for V. vegundo; and Bacillus subtilis and Shigella sonnei for F. ramontchi respectively. The extract of the plants had MIC values ranging from 32 to 128 mg/ml. All plant extracts showed no MIC against Shigella shiga and against Sarcina lutea only C. roseus showed MIC 128 mg/ml. Conclusion: The results revealed that the ethanolic extracts of the plants under present investigation have notable antimicrobial activities.

Keywords: Medicinal plants, Antimicrobial screening, MIC, Bacteria.

Location: Department of Applied Chemistry and Chemical Engineering, University of Rajshahi, Bangladesh.

Start Date:

End Date:

Program Area: Resource Development and Management

Commodity: Medicinal Plants

Objectives:

Evaluation of the effectiveness of some medicinal plant extracts against four Gram-positive and five Gram-negative bacteria.

Methodology:

Plant samples and extraction: Leaves of seven medicinal plants viz, An. paniculata, C. roseus, Ad. vasica, V. vegundo, Al. vera, F. ramontchi and N. arbortristis under present investigation were collected dried and separately grinded with a grinding machine to get powered materials. The powdered leaves were separately extracted with ethanol and the extracts were concentrated under reduced pressure. Source of test microorganisms: Four Gram-positive bacteria (Bacillus megaterium, Staphylococcus aureus, Bacillus subtilis, Sarcina lutea) and five Gram-negative bacteria (Shigella shiga, Salmonila typhi-A, Escherichia coli, Shigella sonnei, Shigella dysenteiae) were collected from the Department of Pharmacy and the Department of Biochemistry and Molecular Biology, University of Rajshahi for determination of antimicrobial activity. Preparation of fresh culture, standard discs and test samples: Slants were prepared by dispersing about 5 ml of nutrient agar media in each test tube. The test tubes were sterilized in an autoclave at 121^oC under a pressure of 15 lb/sq. inch for 15 min. The sterilized test tubes were held in inclined position for solidification. The test tubes were then incubated at 37.5°C. The test organisms were transferred from the culture medium to the slants. These were then incubated at 37.5°C for 24 h. These fresh cultures were used within 2-3 days. Antibacterial activity: Antibacterial activity of the ethanolic extracts were evaluated by the disc diffusion method (Bauer et. al. 1966). The extracts were compared using kanamycin (30 μg/disc) as standard disc. Filter paper along with residual solvent was used as negative control. Crude ethanolic extracts of the leaves of above medicinal plants were dissolved separately in methanol to produce solutions having concentrations of 300-, 400- and 500 μg/μl. Fresh culture of the test organisms in the slants were transferred into the plates of different pretridishes. Sample discs and standard disc were placed on the solidified agar plates. These were kept at 4°C in a refrigerator for 24 h in order to diffuse the extracts and antibiotics in the culture medium. The plates were incubated at 37.5°C for 24 h. The antimicrobial activities of the crude ethanolic extracts were estimated by measuring the diameter (mm) of the zone of inhibition of the organism. In each case, this was compared to that of standard sample. Determination of minimum inhibitory concentrations (MIC): The above mentioned bacteria were utilized for determining the MIC of the ethanolic extracts. Nutrient broth medium and culture media were prepared following the standard methods (Reiner 1982). Kanamycin (30 μg/disc) was used as standards disc. Crude ethanolic extracts of the leaves of the above medicinal plants were transferred in separate vials containing 2% DMSO solution (2 ml). This was mixed well to achieve sample solutions having concentration 1024 μg/ml. Nine sterilized test tubes containing 1-, 2-, 4-, 8-, 16-, 32-, 64-, 128- and 256 μg/ml sample solutions were prepared by serial dilution. Three test tubes containing media (CM), media plus sample (CMS) and media plus inoculums (CMI) were also maintained. Diluted inoculums (10 μl) was added to each of the nine test tubes and mixed well. One ml of the sample was added to CMS and mixed well. 10 μl of inoculums was added to CMI to observe the growth of the organisms in the media. CM containing media was used the check the sterility of the solution. The test tubes were incubated at 37.5°C for 24 h. The lowest concentration of the extracts which inhibited microbial growth was recorded as the MIC.

Source of Information: J. bio-sci. 18: 128-133, 2010 ISSN 1023-8654

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

From the foregoing evidences, it can conclude that the ethanolic extracts of the plants under present investigation possess appreciable antibacterial activities. The MIC values of the extracts have remarkable significance about the therapeutic effects of the active principles associated with the leaves of the plants.

Knowledge Management: Journal