In Vitro Evaluation of Ethanolic and Aqueous Crude Extracts of Newbouldia laevis Leaves on Bacterial Isolates from Ear Infections

The antibacterial effects of ethanolic and aqueous crude extract of leaves of Newbouldia laevis were evaluated against pathogenic Staphylococcus aureus, Staphylococcus epidermidis, Bacillus spp, Pseudomonas aeruginosa and Escherichia coli isolated from ear infections. A concentration gradient of the ethanolic and aqueous extract (12.5 mg/ml – 100 mg/ml) was prepared and its effectiveness was tested by agar well diffusion method and nutrient broth dilution technique. The organisms tested varied in pattern of susceptibility but were more sensitive at high concentrations. The zone of inhibition of aqueous extract of Newbouldia laevis on test organisms ranged from 4.0 to 15 mm while the ethanolic extracts of Newbouldia laevis on test organisms ranged from 6.5 to 21.00 mm. The comparative susceptibility of test bacteria to Newbouldia and ciprofloxacin showed that there was a significant difference in the antibacterial activity of leaf extract and the antibiotic standard. The MIC values ranged from 12.5 mg/ml to 25 mg/ml. The extract showed a higher antibacterial activity against E. coli, Bacillus spp and S. epidermidis. The result of the study suggests that the leaf extract of N. laevis has the potential and could be used as a source for new broad spectrum antibiotics to treat ear infections caused by test organisms. Introduction Ear infection is one of the most common diseases occurring throughout the world. About 65–330 million people suffer from ear infection worldwide and 60% of them have significant hearing impairment [1]. If left untreated long term consequences of persistent severe ear infection can arise including speech disorder, hearing loss and lower overall quality of life [2, 3]. Many studies have reported high level of resistance pattern to different antibiotics from bacterial isolates from ear infections [4, 5]. Thus due to aforementioned reasons, it is pertinent to look for affordable and convenient alternative medicine with a view to providing better protection and treatment. Newbouldia laevis (P. Beauv) seem is a medicinal plant that belongs to Bignoniaceae family. It is popularly known as the tree of life’ and African Border Tree’. Its local Nigerian names include Aduruku in Hausa, Ogirisi in Igbo, Akoko in Yoruba language, Kontor in TIV, Ikhimi in Bini and Ogiriki (Urhobo). It grows to a height of about 7–8 (up to 15) m, more usually as shrub of 2–3 m, many stemmed forming clumbs of gnarled branches [6, 7]. It is native to tropical Africa and grows on moist and well drained soils; extends from Guinea Savannahs to the dense forest zone. In Nigeria, it has been found useful as a remedy for earache, sore feet, chest pain, epilepsy and children’s convulsion [8]. Anti-bacterial activity of the leaf extract have also been studied and reported [7, 9]. As it has been asserted that Newbouldia laevis have potential activity against bacteria hence this work was undertaken at investigating the antibacterial potential of ethanolic and aqueous extracts of leaf of N. laevis against bacteria isolates from ear infections. International Journal of Pharmacology, Phytochemistry and Ethnomedicine Submitted: 2017-08-16 ISSN: 2297-6922, Vol. 9, pp 18-23 Revised: 2018-01-22 doi:10.18052/www.scipress. com/IJPPE.9. 18 Accepted: 2018-03-26 2018 SciPress Ltd, Switzerland Online: 2018-04-13 SciPress applies the CC-BY 4.0 license to works we publish: https://creativecommons.org/licenses/by/4.0/ Materials and Methods Collection of Plant Materials Fresh leaves of N. laevis were collected in the month of June, 2016 from Calabar Street, Aba, Abia State, Nigeria. The plants were botanically identified in the herbarium section of the Department of Biology/Microbiology, Abia State Polytechnic, Aba. Preparation of the Plant Materials The leaves were washed with distilled water; air dried at room temperature for 2 weeks and finally grounded using a mechanical blender. The powdered sample was kept in an air tight container until required for further experiments. Extraction Procedures The method described by Akerele et al. [10] with slight modification was used for the extraction procedure 250g of the powdered leaf was extracted in 100ml (70%) ethanol and water respectively using maceration method for 48 hours. The crude extract was decanted and filtered using Whatman No. filter paper. The filtrate was concentrated to a semi solid residue using water bath at 75.5c after which the solid residue was stored in an air tight bottle in a refrigerator. Different concentrations of the extracts at 100, 50 and 25 mg/ml were freshly prepared by re-dissolving the dried power in the same solvent which was used for the extraction. Preparation of Antibiotic Dilution The antibiotic ciprofloxacin was reconstituted by dissolving 0.5mg of powder in 100ml of distilled water so as to get a concentration of 30μg/ml. The prepared dilution of the antibiotic was used for subsequent antibacterial test and served as a positive control. Collection of Clinical Specimens Patients attending private and primary health care centers in Aba presenting with ear infections were enrolled for the study. Ethical clearance was gotten from ethics committee of the various health centers and permission sought from management of private hospitals used. Patients consent was first obtained before collection of specimens which were done with assistance of hospital staff. Using a sterile swab stick moistened in normal saline, the inner surfaces of the infected ear were gently swabbed and then the swabs promptly taken to the Microbiology laboratory of Abia State Polytechnic, Aba for further analysis. Isolation and Identification of Bacteria 50 ear swab samples were cultured on MacConkey agar, blood agar and chocolate agar plates and then incubated aerobically at 37c for 24 hours. After incubation for 24 hours, individual well separate colonies were picked and further sub cultured so as to obtain pure colonies. Pure isolates were identified using standard microbiological procedures as described by Cheesbrough [11]. Preparation of Inoculum The standardization of culture was done according to the method of Clinical and Laboratory Standard Institute [12]. 2mm diameter colonies of the 18h culture of an organism were picked with a sterile wire loop and immersed into a sterile bottle containing Mueller Hinton Broth (Hi media) and was incubated for 5h – normal saline was added gradually to it so as to compare the turbidity to that of 0.5 McFarland standard corresponding to approximately 1.0 x 10 cfu/ml. International Journal of Pharmacology, Phytochemistry and Ethnomedicine Vol. 9 19