Submit Manuscript | http://medcraveonline.com Introduction Plants and plant derived metabolites are believed as rich sources of antimicrobial agents. A wide range of plants and their parts are used for their medicinal properties by local communities and folklore healers. Plants possess varieties of secondary metabolites with antimicrobial properties. The studies on plant derived polyphenolic compounds confrmed the antimicrobial, antioxidant, anticancer and apoptosis inducing properties of the plants and supplemented effective usage of medicinal herbs against microorganisms. 1,2 With the impact and less side effects, the herbal medicine is practiced as complementary and alternative medicine day by day in developing countries. 3,4 Plants and plant derived products are the cheapest, easily avialable and safer alternative sources of antimicrobials. 5-7 The phytochemical and pharmacological studies on the roots of P. zeylanica confrmed antiplasmodial, 8 antimicrobial, 9 antifungal, 10 anti infammatory and anticancer, 11 antihyperglycemic, 12 hypolipidaemic and anti atherosclerotic, 13 properties of the plant. The ethnobotanical knowledge and biological studies on the aerial parts or roots of P. auriculata suggested that root and aerial parts of P. auriculata are employed to control black water fever, 7 plant are used as anti feedant 14 and antifungal agents to control spore germination of Macrophomina phaseolina. 15 The ethanolic leaf extract of P. rosea is active against herpus simplex virus type I. The root of P. rosea was used to treat digestive problems, dyspepsia, colic cough and bronchitis. 16 Ibrahim et al., 17 studied the antibacterial potentials of P. indica. Devi et al., 18 screened the antibacterial effcacies of P. zeylanica leaf extracts. Vishnukanta & Rana 19 studied the anti convulasant activity Plumbago zeylanica, Jeyachandran et al., 20 evaluated the antibacterial activity of plumbagin and root extracts of Plumbago zeylanica, Rahman & Anwar 21 screened the antimicrobial activity of Plumbago zeylanica root crude extract. Parekh & Chanda 22 studied the antibacterial potentials of P. zeylanica. Tharmaraj & Antonysamy 23 screened the antibacterial effcacy of P. rosea from Chankanachari, Kerala. Most of the studies were focused on the antimicrobial potentials of P. zeylanica roots only; very few reports are available on aerial parts of the selected Plumbago species of Tamil Nadu. There is no report on the antimicrobial actvities of Plumbago auriculata. There is no report on the antimicrobial actvities of Plumbago auriculata. To supplement the previous observations, an attempt has been made to reveal the bactericidal activity of three selected Plumbago species viz., Plumbago zeylanica Linn., Plumbago auriculata Lam. and Plumbago rosea Linn. aerial parts. Materials and methods Preparation of extracts For bioeffcacy studies, the aerial parts of Plumbago zeylanica Linn., Plumbago auriculata Lam. and Plumbago rosea Linn. were collected from Papanasam (Tamil Nadu), Tenkasi (Tamil Nadu) and Dana (Tamil Nadu) respectively. The collected Plumbago species were washed thoroughly with tap water followed by distilled water. The washed Plumbago species were blotted on the blotting paper and spread out at room temperature in shade to remove the excess water contents. The shade dried plant samples were ground to fne powder using mechanical grinder. The powdered samples were stored at 4°C for further use. The dried and powdered aerial parts of Plumbago species were extracted successively with 30g of plant powder and 180ml of petroleum ether, chloroform, acetone, ethyl acetate, ethanol and J Microbiol Exp. 2015;2(6):194‒200. 194 ©2015 Tharmaraj et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and build upon your work non-commercially. Screening of bactericidal activity of selected Plumbago species against bacterial pathogens Volume 2 Issue 6 - 2015 Renisheya Joy Jeba Malar Tharmaraj, Johnson Marimuthu Antonysamy Department of Botany, Centre for Plant Biotechnology, India Correspondence: Johnson Marimuthu Antonysamy, Centre for Plant Biotechnology, Department of Botany, St. Xavier’s College (Autonomous), Palayamkottai, Tamil Nadu, India, Tel +979786924334, Fax +914622561765, Email Received: July 28, 2015 | Published: December 03, 2015 Abstract The present study was undertaken to determine the antibacterial potential of Plumbago species viz., Plumbago zeylanica Linn., Plumbago auriculata Lam. and Plumbago rosea Linn. collected from various localities of South India. For the bio-effcacy studies six different extracts of Plumbago species with various concentrations viz., 20, 40, 60, 80 and 100µg/ml against gram positive and gram negative bacterial pathogens viz., Staphylococcus aureus (MTCC 737), Streptococcus pyogenes (MTCC 1928), Bacillus subtilis (MTCC 441), Klebsiella pneumoniae (MTCC 109), Morganella morganii (MTCC 662) and Pseudomonas aeruginosa (MTCC 1688) using well diffusion method. Among the eighteen different extracts of three different Plumbago species, highest frequency of antibacterial activity (54%) was recorded in P. rosea. The antibacterial activity of various extracts in different concentration of the selected Plumbago species are as follows: P. rosea (54%) > P. zeylanica (49%) > P. auriculata (40%). The ethanolic extract of all the Plumbago species revealed superior bactericidal activity compared to other tested extracts. The ethanolic extracts of P. zeylanica, P. auriculata and P. rosea showed 91%, 50% and 99% of activity against Gram positive pathogens and 66%, 26% and 89% of activity against Gram negative pathogens. The bioactive compound plumbagin and extract of aerial parts of Plumbago species show a wide spectrum of antibacterial activity. The compound shows promise as a new drug for various bacterial infectious diseases. Hence, this study offers a base of using Plumbago species as herbal alternative for the synthesis of antimicrobial agents. Keywords: bactericidal, Plumbago species, antibacterial, extracts Journal of Microbiology & Experimentation Research Article Open Access