*Corresponding Author Address: Dr. Anthony A. Adegoke Department of Microbiology, University of Uyo, P.M.B. 1017 Uyo, Akwa Ibom State, Nigeria; aayodegoke@gmail.com; anthonyadegoke@yahoo.co.uk World Journal of Pharmaceutical Sciences ISSN (Print): 2321-3310; ISSN (Online): 2321-3086 Published by Atom and Cell Publishers © All Rights Reserved Available online at: http://www.wjpsonline.org/ Original Article Antifungal activity and Nystatin Interaction with crude aqueous and Methanolic extracts of Azadirachta indica (Neem) on some fungal isolates A.A. Adegoke and N.U. Asamudo Department of Microbiology, University of Uyo, P.M.B. 1017 Uyo, Akwa Ibom State, Nigeria. Received: 14-03-2017 / Revised: 23-04-2017 / Accepted: 26-04-2017 / Published: 26-04-2017 ABSTRACT Antifungal activities of crude aqueous and methanolic extracts of Azadirachta indica on some fungal isolates were determined. Standard microbiological methods and methods in phamacognosy were used to determine phytochemistry, for antibiotic susceptibility testing (AST), and antibiotic-extract interaction. The results obtained from this research showed higher quantity of saponins in methanolic extracts while terpenes were more in aqueous extracts. The antifungal effect showed by the extracts increased with increasing concentrations (12.5 mg/mL, 25.0 mg/mL, 50 mg/mL, 100 mg/mL, 200 mg/mL) on Aspergillus niger (inhibition zone range: 10.2 ± 0.2 mm-19.5 ± 0.1 mm) Penicillium sp. (inhibition zone range: 6.0 ± 0.2 mm-16.3 ± 0.5 mm) and Candida albicans (inhibition zone range: 8.3 ±2.0 mm- 18.0 ± 1.2 mm) for both methanolic and aqueous extracts. Aqueous extracts showed higher potency than methanolic extracts (p < 0.01). Activity index as high as 1.8 was observed. MIC as low as 125 μg/mL and 250 μg/mL were also observed. Combined extract and nystatin at MIC and ½ MIC showed synergy against Aspergillus niger and Candida albicans, but showed indeterminate effect on Penicillium sp. The traditional use of Neem plant for treating diverse infectious diseases is hereby justified, while its combination with synthetic antifungal drugs when necessary would be effective. Keywords: methanolic extracts, aqueous extracts, synergy, antagonistic, infectious disease INTRODUCTION There is an increasing demand for medicinal plants and plants products as alternative to orthodox medicines especially in developing countries [1-3]. Reports of proximate analysis show that plants like neem consists of essential molecules, including ascorbic acid (n-hexacosanol) and amino acid (7- desacetyl-7-benzoylazadiradione, 7-desacetyl-7- benzoylgedunin, 17-hydroxyazadiradione) [4]. This justifies the use of such medicinal plants by traditional healers with positive therapeutic results [5]. Different parts used in folklore medicine include: root, stem flower, fruit, twigs, exudates and modified plant organs. Some of these raw drugs of medicinal plants are collected in smaller quantities by the local communities and folk healers for local uses. Many other raw drugs are collected in larger quantities and traded in the market for many herbal industries [6], supporting the need to study the potentials as antimicrobial agent. Azadirachta indica (neem) is an evergreen tree that has been used as a traditional medicine for centuries in the Indian culture and many tropical countries [5]. It is a fast growing tree that can reach a height of 15-20 meters (49-66ft) [7]. Neem plants‘parts have been used locally to boost immune system, treat malaria, wounds and swellings; and has been rationalized by some formal reports [8, 9]. Meanwhile, the need for potent antifungal drugs continues as ever [10]. Fungal infections are estimated to occur in over a billion people each year and recent evidence suggested the rate is increasing. [11, 12]. Fungi can infect any part of the body including skin, nails, respiratory tract, or can be systemic [10]. If fungal infections enter systemic circulation, consequences can be deadly [13]. There are limited therapeutic options for invasive fungal infections [10]. Three classes of antifungal molecules are currently used in clinical practice and in the last three decades, only one new class of antifungal drugs have been developed [10]. It is therefore worthwhile to further study neem’s antifungal activity and the effects of its combined administration with an existing antifungal drugs, while also considering its phytochemistry, for which the study aimed.