Indo Global Journal of Pharmaceutical Sciences, 2020; 10(4): 88-95 88 Effect of Selected Plant Extracts on Plaque Associated Bacterial Isolates and LC-MS/MS based Characterization of their Bioactive Compounds Apoorva Udayashankara, Hemavathy E., Tessy Anu Thomas, K. Manjunath * Department of Microbiology and Biotechnology, Bangalore University, Bangalore, India Address for Correspondence: K. Manjunath, ushamanjunath58@rediffmail.com ; apoorvaudayashankar@gmail.com Received: 03.12.2019 Accepted: 01.05.2020 Published: 20.12.2020 Keywords Oral isolates, antibacterial activity, column chromatography, LCMS/MS, Naringin. INTRODUCTION Oral health is the reflection of our total body health. The human microbiome is a very complex yet a stable environment, harboring a diverse range of microorganisms from viruses to protozoan [1]. In spite of the presence of antibacterial agents like lysozyme and lactoperoxidase in our saliva, the oral microorganisms are able to colonize and turn pathogenic under favorable conditions [2]. Dental caries and periodontal infections are the most common dental diseases. Fermentation of the dietary carbohydrates by the oral microorganisms results in acidic end products, which cause the dissolution of the tooth enamel surface, resulting in caries commonly caused by Streptococcus mutans and Lactobacilli sp. It is the plaque that is the primary etiological agent of caries. Plaque is a biofilm formed by the various inter and intra species interactions within the host, which allows the microbes to adhere and colonize on the tooth surface firmly. Most often, this biofilm is harmless, but when bacterial and environmental conditions prevent equilibrium, caries and periodontal disease followed by endodontic infection may occur [3]. Periodontal disease is characterized by the degeneration and inflammation of gums and includes gingivitis and periodontitis. The most common pathogens involved here are Porphyromonas gingivalis, Prevotella INDO GLOBAL JOURNAL OF PHARMACEUTICAL SCIENCES ISSN 2249- 1023 ABSTRACT: Oral health is an integral part of well-being and plants have a huge contribution in the maintenance of oral health and hygiene. We report in this work for the first time, the potent antibacterial activity of methanolic leaf extract of Citrus maxima against the plaque associated bacterial isolates and have identified the bioactive compound responsible for its activity. In this study, four plants Saraca asoca (Sc), Cassia tora (Ct), Ricinus communis (Rc) and Citrus maxima (Cm) claiming their traditional use in maintaining oral hygiene were subjected to Soxhlet extraction using ethyl acetate and methanol solvents. Four bacterial strains namely, Bacillus paramycoides, Pseudomonas aeruginosa, Staphylococcus epidermidis and Enterobacter hormaechei were isolated and identified from the patients with visible plaque. Isolates were tested for their antibiotic sensitivity using Hexa discs and all were found to be sensitive to Gentamicin at 10mcg, showing an average inhibition of 30mm inhibition zone. The antibacterial activity of the plant extracts was screened against the four oral isolates by agar well diffusion method at 100 mg/ml and 25mg/ml concentration where Cm was found to be effective against all the four oral isolates with an average zone of inhibition of 10mm at 25mg/ml concentration. In order to identify the bioactive compound responsible for its activity, Cm leaf extract was subjected to TLC, Column chromatography and the eluted fractions were screened for their antibacterial potential against the isolates at 10mg/ml concentration wherein the second fraction was found to be effective and hence was subjected to LC-MS/MS analysis to identify the bioactive compound. The bioactive compound was identified as Naringin, belonging to the class of flavonoids. © 2020 iGlobal Research and Publishing Foundation. All rights reserved. Cite this article as: Udayashankara, A.; Hemavathy, E.; Thomas, T.A.; Manjunath, K. Effect of selected plant extracts on plaque associated bacterial isolates and LC-MS/MS based characterization of their bioactive compounds. Indo Global J. Pharm. Sci., 2020; 10(4): 88-95. DOI: http://doi.org/10.35652/IGJPS.2020.104012 .