Vol 11, Issue 12, 2018 Online - 2455-3891 Print - 0974-2441 ANTIMICROBIAL ACTIVITY OF AQUEOUS AND ETHANOLIC LEAF EXTRACTS OF ANACARDIUM OCCIDENTALE SHOBHA KL 1 , AMITA SHOBHA RAO 1 *, PAI KSR 2 , SUJATHA BHAT 1 1 Department of Microbiology, Melaka Manipal Medical College (Manipal Campus), Manipal Academy of Higher Education, Manipal, Karnataka, India. 2 Department of Pharmacology, Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India. *Email: amitarao@rediffmail.com Received: 13 August 2018, Revised and Accepted: 17 September 2018 ABSTRACT Objective: The objective of this study was to evaluate the antimicrobial activity of leaves of Anacardium occidentale (A. occidentale) against microorganisms including multidrug-resistant (MDR) bacteria. Methods: Agar well diffusion method was employed to demonstrate the antimicrobial activity of leaves A. occidentale. Ethanol and aqueous extracts of the leaves were used against microorganisms, which included American type culture collection strains of Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Enterococcus faecalis, and Pseudomonas aeruginosa and the clinical isolates of Streptococcus pneumoniae, Candida albicans, MDR Escherichia coli, and MDR Klebsiella pneumoniae. Results: The ethanolic extract of leaves of A. occidentale showed significant antimicrobial activity. Aqueous extract had mild antifungal activity. Conclusion: Ethanolic extract of leaves of A. occidentale could be a good source for the antibacterials to combat MDR bacterial infections. Further studies are necessary for these potent plant extracts to evaluate the in vivo efficacy and toxicity. Keywords: Leaves of Anacardium occidentale, Antimicrobial susceptibility testing, Multidrug-resistant bacteria. INTRODUCTION Multidrug resistance (MDR) is increasing both in community and health-care associated bacterial infections worldwide. This has impaired the current antimicrobial therapy, thereby creating a demand for other alternatives. There is a demand for medicinal plants in health-care system and the use of these has been associated with fewer side effects [1]. Nowadays, bacteria such as Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), Klebsiella pneumoniae (K. pneumoniae), and Enterobacter species have acquired resistance to the commonly used antibiotics [2-5]. The treatment options for these microorganisms are less and treating physicians are compelled to use expensive drugs like colistin that is associated with significant side effect to the patient’s health [6]. Therefore, there is a need for the development of alternate drugs to prevent the infections caused by these organisms. Medicinal plants are rich sources of antimicrobial agents. Herbal plants have attained a significant role as therapeutic agents [7]. Anacardium occidentale (A. occidentale) a native of Brazil, a tropical evergreen tree, almost all the plant parts, namely bark, leaves, fruit, flower, and nut oil, have been reported to be useful to cure many diseases such as venereal diseases, diarrhea, skin diseases, stomatitis, bronchitis, psoriasis, toothaches, and gum problems [8-10]. Leaves of which contain pharmacologically rich components such as alkaloids, essential oils, tannins, saponins, and cardenolides [11, 12] and are known to have cosmetic [13], antimicrobial [14], and antioxidant [15] properties. In this study, antimicrobial activity against selected bacterial and fungal strains was performed using ethanol and aqueous extract of A. occidentale leaves. MATERIALS AND METHODS Plant collection The fresh leaves of A. occidentale were collected from the plantation area of Udupi, Karnataka, India. Its botanical identity was authenticated by a botanist. Aqueous and ethanol extraction Leaves of A. occidentale were washed with distilled water and air dried at room temperature for 10 days. Fine powder was made by pulverizing with clean mortar and pestle, then stored in a sterilized glass container at room temperature (25–30°C). By Soxhlation method, the ethanol extract of leaves was prepared [16]. The aqueous extract of the leaves was prepared by crushing the leaves in mortar and pestle using sterile distilled water in the ratio of 1:1. Antimicrobial activity Agar well diffusion method was employed to study the antibacterial and antifungal susceptibility [17] Antimicrobial susceptibility was determined using American type culture collection (ATCC) strains, MDR strains, and fungus. The ATCC strains were S. aureus ATCC 25923, Enterococcus faecalis ATCC 29212, K. pneumoniae ATCC 700603, E. coli ATCC 25922, and Pseudomonas aeruginosa ATCC 27853 and clinical strains of Streptococcus pneumoniae (S. pneumoniae), MDR E. coli, MDR K. pneumoniae, and Candida albicans (C. albicans). Ampicillin disc (10 µg), oxacillin disc (1µg), gentamicin disc (10 µg), and ketoconazole disc (10 µg), obtained from Hi-Media, Mumbai, were used as controls. Culture media used were Sabouraud’s dextrose agar (SDA), Muller- Hinton agar (MHA), and blood agar (for S. pneumoniae) which were procured from Hi-Media, Mumbai. The above-mentioned bacterial and fungal strains were identified by standard procedure. Isolated bacterial colonies were transferred to sterile Mueller-Hinton broth, and C. albicans was inoculated to Sabouraud’s dextrose broth and incubated at 37°C overnight. The concentration of growth of microorganisms to 10 5 CFU/ml was adjusted using 0.5 McFarland’s turbidity standard. © 2018 The Authors. Published by Innovare Academic Sciences Pvt Ltd. This is an open access article under the CC BY license (http://creativecommons. org/licenses/by/4. 0/) DOI: http://dx.doi.org/10.22159/ajpcr.2018.v11i12.29073 Research Article