http://elynsgroup.com Copyright: © 2017 De Soyza SG, et al. Open Access Research Article Journal of Molecular Nanotechnology and Nanomedicine J Mol Nanot Nanom Page 1 of 6 Antimicrobial Potential in Biogenic Silver Nanoparticles Synthesized from Plectranthus zeylanicus Sudhara G. De Soyza 1 , W.M.D Gaya Bandara Wijayaratne 2 , Mayuri Napagoda 1 * and Sanjeeva Witharana 3 1 Department of Biochemistry, Faculty of Medicine, University of Ruhuna, Galle 80 000, Sri Lanka 2 Department of Microbiology, Faculty of Medicine, University of Ruhuna, Galle 80 000, Sri Lanka 3 Faculty of Engineering, Higher Colleges of Technology, Ras Al Khaimah, United Arab Emirates Abstract Out of all metals, silver has been widely recognized for its antimicrobial activity over centuries of years. In more recent times, silver was found to be even more effective in antimicrobial activity when it was at nanoscale. A novel protocol was developed for green synthesis of silver nanoparticles and their anti-bacterial activity was experimentally validated. This protocol is different from the prior art in a way that the green synthesis from non-polar organic plant extracts is now possible for the first time. The raw material was the dichloromethane extract of Plectranthus zeylanicus, a widely used medicinal plant in Sri Lanka. Scanning electron microscopy (SEM) images of the formulation revealed that the synthesized objects were predominantly of spherical shape and approximately 100 nm in size. Energy dispersive X-ray (EDX) spectrum confirmed the presence of elemental silver in it. The presence of phytochemical classes that could be responsible for the green synthesis of nano silver was detected by standard qualitative phytochemical screening assays. The antibacterial activity of the compound was assessed by the agar well diffusion method against Gram positive and Gram negative bacteria including the methicillin resistant Staphylococcus aureus (MRSA). These new formulations exhibited profound antibacterial activity against all the tested microorganisms in comparison to aqueous silver ion solution and commercial disinfectants that contain silver ions as active ingredients. This is the first time the anti-MRSA potential of silver nanoparticles synthesized via a green route is documented. Present findings point towards the possible application of biogenic silver nanoparticles as an effective antimicrobial agent against nosocomial infections. Keywords: Antimicrobial; Nosocomial; Biogenic; Plectranthus zeylanicus; Green synthesis; Silver nanoparticles Abbreviations DCM: Dichloromethane; EDX: Energy-dispersive X-ray; MIC: Minimum Inhibitory Concentration; MRSA: Methicillin resistant Staphylococcus aureus; SEM: Scanning Electron Microscopy. Introduction The outbreak of new infecting diseases and the evolution of commensal and pathogenic microorganisms to problematic strains due to the acquisition of resistance to currently employed antimicrobial agents have become critical issues especially in the hospital settings. Acquisition of antimicrobial resistance is associated with negative outcomes that include increased mortality and morbidity, increased length of stay in the hospital, and the requirement of more costly alternative antimicrobial therapy and infection control interventions [1]. Thus the development of novel antimicrobial substances with diverse chemical structures and novel mechanisms of actions has been highly emphasized by the scientific community. Metals and metalloids have been widely employed in the field of medicine for thousands of years owing to their antimicrobial properties. For example, the empirical usage of silver, copper and zinc was prevalent until the discovery of antibiotics in the 20 th century. However, due to the consecutive outbreaks of multidrug- resistant pathogens and the scarcity of remedial antimicrobials in the pipeline, a revival of antimicrobial metals is observed in the recent years [2]. Current developments in the field of nanotechnology have led to the enhancement of intrinsic antimicrobial activity of the metals, when they are in the form of nanoparticles. For example Dobrucka et al. [3] witnessed the ZnO nanoparticles inhibit the growth of Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa; Shamaila et al. [4] recorded nano Au activity against E .coli, S. aureus, Bacillus subtilis and Klebsiella pneumonia; Roy et al. [5] observed nano CaO active against P. aeruginosa and Staphylococcus epidermidis; Kasha et al. [6] reported CuO nanoparticles inhibit E. coli, P. aeruginosa, Proteus vulgaris and S. aureus [6], and Zimbone et al. [7] noticed the nano TiO 2 activity on E. coli; to name a few. Nonetheless silver is the more effective antimicrobial agent against bacteria, viruses and other eukaryotic microorganisms than other metals such as copper, titanium, magnesium, zinc or gold [8], and therefore the most widely examined inorganic nanomaterial for an antimicrobial agent [9–14]. Since the conventional chemical and physical methods involved in the synthesis of metal nanoparticles are costly and potentially harmful to the environment, recently, the attention is paid on the green synthesis of metal nanoparticles as an alternative, efficient, inexpensive, and environmentally safe approach. It is well evident that the reductive capacities of the proteins and metabolites present in plants, algae, bacteria, yeast, fungi etc. could significantly contribute to the transformation of inorganic metal ions into metal nanoparticles. Among these organisms, plants seem to be the best candidate and are suitable for rapid, large scale biosynthesis of nanoparticles of high stability. It is speculated that the various plant metabolites, such as terpenoids, polyphenols, sugars, alkaloids, phenolic acids, and proteins, could play an important role in the bioreduction of metal ions, yielding nanoparticles [15]. Sri Lanka is a country blessed with a great wealth of medicinal plants that could harbor diverse chemical components of high pharmacological potential; nevertheless, a large portion of Sri Lankan flora remains phytochemically and pharmacologically unexplored. Thus the present investigation is focused on harnessing the secondary metabolites in a popular medicinal plant in Sri Lanka, Plectranthus zeylanicus, for the biosynthesis of silver nanoparticles and evaluation of possible antimicrobial effects of the prepared silver nanopreparations. In contrast to the prior studies where the aqueous or hydro-alcoholic extracts of plants have been utilized for the green synthesis, the synthetic capacity of the low polar secondary metabolites in lipophilic plant extracts in the generation of biogenic nanoparticle was evaluated in this study. Received Date: April 29, 2017, Accepted Date: June 13, 2017, Published Date: June 20, 2017. *Corresponding author: Mayuri Napagoda, Department of Biochemistry, Faculty of Medicine, University of Ruhuna, Galle 80 000, Sri Lanka, Tel: +94-071- 921-6281; Fax: +94-912-222-314; E-mail: mayurinapagoda@yahoo.com.