Antibacterial Activity And Phytochemical Screening Of Crude Ethanolic Extract Of Leaves Of Ocimum Gratissimum L On Listeria Monocytogenes.
T Mbata, A Saikia
T Mbata, A Saikia. Antibacterial Activity And Phytochemical Screening Of Crude Ethanolic Extract Of Leaves Of Ocimum Gratissimum L On Listeria Monocytogenes.. The Internet Journal of Microbiology. 2007 Volume 4 Number 2.
Ethanolic extract of the leaves of
Medicinal plants have contributed immensely to health care in Nigeria. This is due in part to the recognition of the value of traditional medical systems, particularly in Asian origin, and the identification of medicinal plant from indigenous pharmacopoeias, which have significant healing power.
Among all families of the plant kingdom, members of the Lamiaceae have been used for centuries in folk medicine.
Recent studies on
It is said to have numerous properties, such as the tannins and sweet smelling volatile oil known to have antibacterial agent (Elujoba, 2000). The volatile oil also stops spasm, the hyperactivity of the gastrointestinal tract, by combining with the antibacterial activity and thus lowers the amount of times the muscle of the stomach and gastrointestinal tracts contracts stopping the diarrhoea (Elujoba, 2000) that are usually adverse for most other pathogenic bacteria. It can be isolated from soil, silage and other environmental sources (Patrick
The onset of Listeriosis is usually preceded by influenza-like symptoms (Martin and Fisher, 2000). The onset time to serious forms of Listeriosisis is known but may range from a few days to 3 weeks. The manifestation of Listeriosis is septicemia, meningitis (or meningoencephalitis), encephalitis, and intrauterine or cervical infections in pregnant women, which may result in spontaneous abortion or stillbirth. At present the infective dose of
Over the past few years there have been published many studies that associate the consumption of foods contaminated by
This study was designed to evaluate the antibacterial efficacy of
Materials And Methods
Collections and Identification
Fresh leaves of
Processing of Plant Samples
The fresh leaves were harvested and properly washed in trap water and then rinsed in sterile distilled water. The leaves were blended fresh using electric blender. The soluble ingredients were then extracted by solubilization using ethanol as solvent.
Extraction of Plant Material
The ethanol extract of the active ingredient of the leaves were carried out using the method as described by (Harbone 1994). 25g of the grinded fresh leaves were soxhlet extracted using 250 ml of 95% ethanol. The extraction lasted for 6 hours. The volatile oil obtained was concentrated by evaporation using water bath at 100oC for 1 hour.
Preparation of Crude Extract
The method of Akujobi
The strain used in this work was
The antibacterial tests of the plant extracts were tested on the test isolate using the agar-gel diffusion inhibition test. In the agar-gel diffusion inhibition test as described by Opara and Anasa (1993), 0.2 ml of a 24 hours broth culture containing 1 X 106 cells/ml of organism was asceptically introduced and evenly spread using bent sterile glass rod on the surface of gelled sterile Mueller-Hinton agar plates. Three wells of about 6.0 mm diameter were asceptically punched on each agar plate using a sterile cork borer, allowing at least 30 mm between adjacent wells and between peripheral wells and the edge of the petri dish. Fixed volumes (0.1 ml) of the extract were then introduced into the wells in the plates. A control well was in the center with 0.01 ml of the extracting solvent. The plates were allowed on the bench for 40 minutes for pre-diffusion of the extract to occur (Esimone
Maximum Inhibitory Concentration (MIC)
The MIC of the potent extracts were determined according to the macro broth dilution technique (Tilton and Howard, 1987; Baron and Finegold, 1990). Standardized suspensions of the test organism was inoculated into a series of sterile tubes of nutrient broth containing two-fold dilutions of leaf extracts and incubated at 37oC for 24 hours. The MICs were read as the least concentration that inhibited the growth of the test organisms.
Minimum Bactericidal Concentration (MBC)
The MBCs were determined by first selecting tubes that showed no growth during MIC determination; a loopful from each tube was subcultured onto extract free agar plates, incubated for further 24 hours at 37oC. The least concentration, at which no growth was observed, was noted as the MBC.
This was carried out according to the methods described by Trease and Evans (1989).
The data obtained were statistically analyzed using Analysis of Variance (ANOVA), as described by Snedecor and Cochran (1967).
Table 1 shows the results of the antibacterial effect of the extracts on the test isolate. In general the zone of inhibition decreased with decrease in concentration of the extract. The highest zone of growth inhibition occur with a zone diameter of 25mm at a concentration of 250mg/ml, while the lowest zone of growth inhibition occur with a zone diameter of 6.2mm at a concentration of 50mg/ml.
Table 2 shows the MIC and MBC of the extract on the test isolate. The MIC results indicated that ethanolic extract of the fresh leaf on test organism had MIC of 9.25mg/ml, while MBC had 2.15mg/ml.
Table 3 shows the phytochemical profile of the plant extract. The phytochemical screening showed that the leaf extract of
Discussion And Conclusion
Several species and varieties of plants of the genus Ocimum have been reported to yield oil of diverse nature, commonly known as basilic oils. Craveiro
In the present study, the antibacterial profile and phytochemical screening fresh leaf of
The low minimum inhibitory concentrations observed for ethanolic extracts of the fresh leaf on
Preliminary phytochemical screening revealed the presence of alkaloids, tannins, glycoside, saponin, resins, cardiac glycoside, steroidal terpens and flavonoids. These are believed to be responsible for the observed antibacterial effects. Some workers have also attributed to their observed antimicrobial effect of plant extracts to the presence of these secondary plant metabolites (Nweze
The study has showed that the observed antibacterial effect of
The authors are grateful to Staff of IITA, Ibadan, Nigeria for their technical assistance.