Microsoft Word - 124-725-4-Layout.doc Evaluation of the Antibacterial Activity of Adansonia digitata L. Seed Oil Obtained from Zaria, Kaduna State, Nigeria on Some Strains of Bacteria P.R.O. Edogbanya, E. Dangana, Y. Apeji All Res. J. Biol., 2015, 6, 37-41 The publication cost of this article might be covered by external sponsors. More info for sponsors at: sponsors@arjournals.com ARTICLE                                                                                                                    Issue 3, Vol 6, 2015, 37-41 Evaluation of the Antibacterial Activity of Adansonia digitata L. Seed Oil Obtained from Zaria, Kaduna State, Nigeria on Some Strains of Bacteria P.R.O. Edogbanya*1, E. Dangana2, Y. Apeji2 1 Department of Biological Sciences, Faculty of Science, Ahmadu Bello University, Zaria, Nigeria. 2 Department of Pharmaceutics, Faculty of Pharmaceutical Science, Ahmadu Bello University, Zaria, Nigeria. *Corresponding Author: +23408138381212, ocholiedogbanya@gmail.com Graphical Abstract Abstract The use of essential oils as antibacterial agents have become popular over the years, this is in a bid to search for alternative ways of dealing with strains of bacteria that have become resistant to conventional antibiotics. This study was carried out to evaluate the antibacterial potentials of Adansonia digitata seed oil obtained from Zaria, Kaduna state, Nigeria, on the clinical isolates of some bacteria (Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli). The oil was extracted from the seeds using the soxhlet extraction method with n-hexane as the solvent. The Well diffusion method was used to test the susceptibility of the strains of bacteria to the oil, using Gentamycin and Streptomycin as standard positive controls. Experiments were carried out in duplicates. Data obtained from the experiment was analysed using one-way analysis of variance (ANOVA) and Duncan Multiple Range Test (DMRT), with P < 0.05 considered significant. The results revealed that A. digitata oil was unable to create any inhibition zones in the bacteria cultures. From this research, it can be concluded that A. digitata oil had no Antibacterial activity. Keywords: Adansonia digitata; Antibacterial; Bacteria; Essential oils; seed 37 All Res. J.Biol, 2015, 6, 37-41     Introduction The World health Organisation has reported that diseases caused by pathogenic bacteria are one of the main cause of morbidity and mortality worldwide1. Drug resistance has become a mitigating factor in the effective treatment of many bacterial diseases, therefore, there is an intense search for alternative methods of treating these diseases2, 3. Many plants are known to contain essential oils (also known as volatile oils) which are aromatic in nature. These oils are by-products of metabolism secreted by special glands and stored up in various parts (such as leaves, flowers, roots, buds, twigs, rhizomes, bark, seeds and fruits etc.), and are aromatic in nature. From time immemorial the antimicrobial properties of essential oils have been known. The ‘first-aid' kit containing myrrh essential oil was used by few Greek soldiers in the battlefield to treat wounds and was introduced by physician Galen4. Many of them have been screened for their potential uses as alternative remedies for the treatment of many infectious diseases5. Adansonia digitata L. – Baobab (commonly known as “Kuka” in northern Nigeria) is a deciduous tree belonging to the Malvaceae family and is indigenous to arid central Africa6, 7. It is a large imposing tree which reaches heights of about 18-25 m and produces a rounded crown showing a stiff branching habit. It has a peculiarly swollen trunk of up to 10 m in diameter, usually tapering or cylindrical and abruptly bottle- shaped; often buttressed. Giant individuals can reach a girth of up to 28 m. It is widely distributed and can be found in most of Sub-Saharan Africa’s semi-arid and sub-humid regions as well as in western Madagascar 8. Different parts of the tree are used as foods and medicines including the back fibres. No part of the tree is a waste9, 10, 11, 12. The seeds have a characteristic bean shape and have been reported to contain essential oil11, 12. This research attempts to evaluate the antibacterial efficacy of the seed oil of Adansonia digitata. Materials And Methods Collection of Plant Material Dried fruits of Adansonia digitata were collected from the Department of Biological Sciences, Ahmadu Bello University, Zaria, Kaduna State, Nigeria, and were verified in the herbarium of the Department, with a voucher number of 2512. The fruits were split open and seeds were mechanically removed, properly washed, dried, pulverized into powder using mortar and pestle, sieved through a pore size of about 1mm, and stored in airtight containers. Extraction of Essential Oils The extraction of essential oil was done using n-hexane in electro-thermal soxhlet extractor (Gallenkamp, England). 30 g of powdered seeds was weighed and put into the thimbles of the soxhlet extractor, the apparatus was mounted and allowed to run for 1 hour, after which the mixture of essential oil and n-hexane was collected in a beaker and evaporated over a hot water bath to collect the oil as residue. Bacterial Strains Clinical isolates of Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli were obtained from the Department of Pharmaceutics and pharmaceutical Microbiology, Faculty of Pharmaceutical Sciences, Ahmadu Bello University, Zaria. Overnight cultures obtained using 10 ml nutrient agar were used for the study. Well Diffusion Assays Mueller Hinton's agar was prepared according to manufacturer's instructions, poured into Petri dishes, and allowed to set. The surface of the agar was flooded with 2 ml of isolate and the excess was drained into a disinfectant container. A cork borer was flamed and used to bore three wells in each agar. 100 µml each of undiluted Adansonia digitata oil, 1 mg/ml of Gentamycin and 0.1 mg/ml of Streptomycin (which served as standard positive controls), were put separately in the three wells and allowed to stand for 1 h to diffuse properly. The plates were incubated for 24 h at 37°C and inhibition zones were measured13. The experiments were done in duplicates. Statistical Analysis One way Analysis of Variance (ANOVA) was used to compare the mean inhibition zones of the different treatment groups and Duncan Multiple Range Test (DMRT) was used to separate means where significant. P < 0.05 was considered significant. Results At the end of the experiment, it was observed that A. digitata oil had no inhibitory effect on all the bacteria isolates, this was confirmed by its failure to cause any inhibition zone around the wells containing the oil, 38 All Res. J.Biol, 2015, 6, 37-41     unlike the standard antibiotics used (Table 1 and Figure 1 – 4). Table 1: Mean Inhibition zones of the different treatments on bacterial isolates Mean ± S.E.M; n = 2; means in the same row with different superscripts are significantly different ( P < 0.05). Figure 1: Inhibitory effect of A. digitata oil (A), Gentamycin (G) and Streptomycin (S) on B. subtilis. Figure 2: Inhibitory effect of A. digitata oil (A), Gentamycin (G) and Streptomycin (S) on S. aureus Figure 3: Inhibitory effect of A. digitata oil (A), Gentamycin (G) and Streptomycin (S) on P. aeruginosa Mean Inhibition Zones (mm) Bacteria Gentamycin (1 mg/ml) Streptomycin (0.1 mg/ml) A.digitata oil B. subtilis 37.00 ± 1.00a 39.00 ± 1.00a 0.00 ± 0.00b S. aureus 36.00 ± 0.05b 37.00 ± 0.05a 0.00 ± 0.00c P. aeruginosa 34.50 ± 2.50a 33.50 ± 1.50a 0.00 ± 0.00b E. coli 34.50 ± 0.50a 29.50 ± 0.50b 0.00 ± 0.00c 39 All Res. J.Biol, 2015, 6, 37-41     Figure 4: Inhibitory effect of A. digitata oil (A), Gentamycin (G) and Streptomycin (S) on E. coli Discussion The findings of this research were not in agreement with a similar work of Samie et al. (2012)14 which reported that A. digitata oil was able to weakly inhibit the growth of a number of bacterial organisms, of which P. aeruginosa and S. aureus were amongst them. Although Samie et al. (2012) 14 also acknowledged that even though the oil showed inhibitory effect, it, however, had little bactericidal activity. The failure of A. digitata oil to cause an inhibitory effect on the bacterial organisms used in this study may be due to the fact that it is a weak antibacterial agent, and the strains of bacteria were resistant to it. Djouahri et al. (2013) 15 reported that methods used in the extraction of essential oils causes variation in their chemical composition of the active compounds, and this may also be responsible for the discrepancy in results. Samie et al. (2012)14 used the hydrodistillation method while the soxhlet extraction method was used in this research. Ozcan and Chalchat (2005) 16 reported that location causes a variation in the chemical composition of essential oils and this may be another possible factor that affected the results. Samie et al. (2010) 14 used baobab seeds obtained from the South African region, while the seeds used for this research were obtained from the Central African region (Zaria, Kaduna state, Nigeria). It has also been reported that the hydrocarbon monoterpenes compounds found in essential oils show low antibacterial activity while oxygenated compounds possess high potential, especially phenol type compounds as thymol and carvacrol. Oxygenated monoterpenes, exhibit strong antimicrobial activity, especially pronounced on whole cells, while hydrocarbon derivatives possess lower antimicrobial properties, as their low water solubility limits their diffusion through the medium 17, 18. The limitation of A. digitata oil’s antibacterial activity may be due to the fact that it contains more hydrocarbon monoterpenes than it does oxygenated compounds, although this has not been verified. However other parts of A. digitata have been reported to possess high antibacterial activity such as the root and stem barks 19, fruit pulp 20, and leaves 21. Conclusion From this research, it can be concluded that A. digitata oil had no antibacterial activity against Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. Further research could be done using pure strains of these bacteria and a different method of extraction of oil. References   1. World health Organization (WHO) (1998). The world health Report. Life in the 21st Century: A vision for all 2. Measuring health. (World Health Organization, Geneva, Switzerland), pp. 39-60. 2. Reynolds, J.E.F. (1998). Martindale: The Extra Pharmacopeia (31st Ed.). 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