## 6 Antioxidant and Antimicrobial Properties of _Camelia sinensis_  
_C. sinensis_ leaves contain polyphenols, which have remarkable antioxidant and antimicrobial effects against _Staphylococcus aureus_, _Vibrio cholerae_, _Campylobacter jejuni_, _Staphylococcus epidermidis_, _Vibrio mimicus_, _Listeria monocytogenes_, _Escherichia coli_, _Salmonella typhi_, _P. aeruginosa_, _Helicobacter pylori_, and _Propionibacterium acnes_, amongst others [8; 9; 62; 63; 64; 65; 66; 67; 68; 69; 70]. The antibacterial activity of black tea extract against several pathogenic bacteria, including Gram-positives (_L. monocytogenes and S. aureus_) and Gram-negatives (_V. cholerae and Salmonella enterica serovar_), was investigated by [PERSON], [PERSON], [PERSON], and [PERSON] [67]. [PERSON] et al. [66] conducted a study on green tea leaf extracts to test their antibacterial activity against various bacteria isolated from environmental sources. The chemotherapeutic use of green tea was clearly reflected. All bacterial isolates were identified by Gram staining and biochemical testing. Six different bacteria were identified, including _E. coli_, _Staphylococcus_, _Streptococcus_, _Pseudomonas_, _Bacillus_, and _Proteus species_. The antibacterial activities of extracts were checked by disc diffusion assay. Catechins EGCG, EGC, ECG, EC, and gallocatechin-3-gallate (GCG) were evidenced to play an important role in green tea's inhibition of bacterial growth, involving damage in bacterial cell membranes [71]. The green sorts of tea have shown higher antimicrobial activity than the black ones, due to different phytochemical patterns. Indeed, daily consumption of green tea is able to kill Gram positive _S. aureus_, including many other harmful bacteria. On the other hand, constituents present in tea also possess antimicrobial, anticarcinogenic, and anti-mutagenic properties [67]. The antimicrobial activity of plant extracts also depends on presence of different secondary metabolites, like hydroxyl group on active constituents. These biologically active compounds of plant extracts are considered antimicrobial agents, which are able to inhibit cell wall, protein, and nucleic acid synthesis [71]. EGCG have been reported to have antimicrobial properties [68]. The antimicrobial activity of different tea extracts was evaluated by Spot-On-Lawn and Well Diffusion assays, and the minimum inhibitory concentration (MIC) was determined. These three methods used showed _Brochotthrix thermosphacta_ inhibition, while _Pseudomona putida_ and _E. coli_ inhibition were only detected with MIC assay. Indeed, MIC determination in broth culture appeared to be the most reliable method to determine the effective inhibitory activity of catechin compounds. An acidic polysaccharide from _C. sinensis_ was examined by [PERSON], et al. [72] to characterize its anti-adhesive effects against pathogenic bacteria, most notably _H. pylori, P. acnes,_ and _S. aureus_. This acidic polysaccharide showed marked inhibitory effects against pathogen-mediated hemagglutinin. _C. sinensis_ has been shown to possess antimicrobial properties and to lower the risk of cardiovascular and periodontal diseases [73]. In this study, the antimicrobial effects of brewing green tea were investigated against common oral bacteria, such as _Streptococcus mutans_, _Perplyromonas gingivalis_, and _S. epidermidis_. Gram stain tests revealed that these cultures had a mixture of Gram-positive and Gram-negative bacteria. MIC assay implied a positive correlation between green tea concentration and bacterial growth. _C. sinensis_ crude extracts inhibited in vivo growth of _Candida albicans_, _Candida glabrata_, _Candida tropicalis_, _Candida Krusei_, and _Microsporum persicolor_[74]. [PERSON] et al. [75] demonstrated that _C. sinensis_ has antibacterial and antifungal activities in combination with butylated hydroxyanisole (BHA). Green tea glycolic extract showed only limited activity against _S. mutans_ and no activity against _C. albicans_ and certain _E. coli_ strains.