Short communication Green tea extract: Possible mechanism and antibacterial activity on skin pathogens Anjali Sharma 1,2 , Sonal Gupta 2 , Indira P. Sarethy, Shweta Dang, Reema Gabrani ⇑ Department of Biotechnology, Jaypee Institute of Information Technology, A-10, Sector 62, Noida, 201307 UP, India article info Article history: Received 2 September 2011 Received in revised form 13 April 2012 Accepted 30 April 2012 Available online 11 May 2012 Keywords: Adhesion Anti-microbial Aqueous extract Camellia sinensis Cytotoxicity Green tea Vero cell line abstract Camellia sinensis (tea) is known for its therapeutic properties (anti-inflammatory, anti-microbial, anti- tumour, anti-oxidative and anti-ageing). Although, anti-microbial properties of green tea have been stud- ied, its role against bacterial strains related to skin infections and mechanism of action is not well under- stood. We focussed on exploring anti-microbial activity and the basic mechanism of aqueous green tea leaf extract on selected bacterial strains. Staphylococcus epidermidis, Micrococcus luteus, Brevibacterium lin- ens, Pseudomonas fluorescens and Bacillus subtilis were found to be sensitive to green tea extract via disc diffusion assay (zone of inhibition P7 mm). Minimal inhibitory concentration (MIC) was determined via nitro blue tetrazolium (NBT) assay (0.156–0.313 mg/ml). Moreover, the aqueous extract was found to be not toxic to the Vero cell-line up to a concentration of 500 lg/ml. The effect of aqueous extract on adhe- sion of different bacteria to Vero cells indicated that it inhibits the adhesion at its MIC value. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Many ancient medical systems, e.g. Ayurveda, homeopathy and naturopathy, rely on herbal remedies to treat various skin infections caused by bacterial strains (Farnsworth, Akerele, Bingel, Soejarto, & Guo, 1985). Although, plants synthesise over 100,000 small mole- cules (Dixon, 2001), many of which have antimicrobial activity, very little is known about their mechanisms of action. Plant-derived anti-microbial agents may have only weak action compared to com- mon antibiotics. However, drug resistance, unavoidable side effects and limited specificity restrict the effectiveness of antibiotics. More- over, certain plant-derived drugs can exhibit inhibitory effects, even at a very low dose, especially against Gram-positive bacteria (Gib- bons, 2004) and, therefore, are less likely to be toxic to animal cells. The leaves of Camellia sinensis, a shrub, are consumed as a bev- erage all over the world and have been associated with various medicinal properties. Green tea catechins (GTCs) are polyphenolic compounds present in the unfermented dried leaves of the plant, C. sinensis. Biological and pharmacological activity of green tea leaf extract (anti-inflammatory, anti-microbial, anti-tumour, anti-oxi- dative and anti-ageing) have been attributed to GTCs. GTCs are of four types: epicatechin, epicatechin gallate, epigallocatechin and epigallocatechin gallate. All these GTCs act synergistically; there- fore, the crude green tea leaf extract exhibits higher antimicrobial activity than do isolated GTCs (Hare, 2001, chap. 5). Epigallocate- chin gallate (EGCG) is the most effective and also accounts for about 60–70% of total GTCs. There are various hypotheses which try to explain the mecha- nism of action of C. sinensis. One of these hypotheses is that C. sin- ensis irreversibly damages the bacterial cytoplasmic membrane, which can alter the adhesion of bacteria to the cells (Lee, Shim, Chung, Lim, & Kim, 2009). Hence, it is possible that treatment with C. sinensis leaf extract inhibits the adhesion of bacteria on cell membranes and acts as a potential anti-adhesive agent. However, it has been reported that Gram-negative bacteria are less suscepti- ble to catechins as lipopolysaccharides act as barrier. Other possi- ble mechanisms of C. sinensis include affecting the activity of dihydrofolate reductase (DHFR), an enzyme required by pathogens for the synthesis of purines and pyrimidines and also increasing the epidermal thickness (Chung et al., 2003). The aim of this study was to investigate the effect of an aqueous extract of green tea leaves on bacterial strains known to cause skin infections in humans. One of the possible mechanisms of green tea, to inhibit the growth of bacteria, is to prevent the adhesion of bac- teria to mammalian cells. This hypothesis was ascertained by adhesion assay of green tea extract at its MIC value on Vero cell- line in the presence of the tested bacteria. 2. Materials and methods 2.1. Procurement and maintenance of bacterial strains Bacterial strains, Bacillus subtilis (MTCC1427), Micrococcus luteus (MTCC106), Pseudomonas fluorescens (MTCC2421), Staphylococcus 0308-8146/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.foodchem.2012.04.143 ⇑ Corresponding author. Tel.: +91 120 2594210; fax: +91 120 2400986. E-mail addresses: anjalish1988@gmail.com (A. Sharma), sonal85gupta@gmail.- com (S. Gupta), indirap.sarethy@jiit.ac.in (I.P. Sarethy), shweta.dang@jiit.ac.in (S. Dang), reema.gabrani@jiit.ac.in (R. Gabrani). 1 Present address: B-35, Shekhar Apartments, Mayur Vihar, Delhi 110091, India. 2 These two authors contributed equally to this work. Food Chemistry 135 (2012) 672–675 Contents lists available at SciVerse ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem