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Chemical profile, antioxidant and antimicrobial potential of green tea

The increase in the consumer’s concern about food safety and the use of synthetic additives in food processing has been a challenge for food producers. To replace synthetic chemicals without the loss of food safety, natural compounds rich in bioactive phytochemicals have been intensively investigated. The aim of this study was to determine the phenolic profile, antioxidant and antimicrobial properties of green tea extracts (prepared using ultrasound bath ; 2 h, 60 °C, plant material:water = 15:100). The total phenolic content (TPC) and antioxidant activity (ferric reducing/antioxidant power  FRAP ; 2, 2- diphenyl-1-picrylhydrazyl radical scavenging ability  DPPH) were determined, and antimicrobial activity against common food-borne pathogens, three Gram- positive (Staphylococcus aureus, Enterococcus feacalis, Listeria monocytogenes) and two Gram- negative bacterial strains (Salmonella enterica, Escherichia coli). The phenolic profile, analyzed by HPLC, showed gallic acid, rutin, and epicatechin as the most abundant compounds in green tea extract. The total phenolic content was determined by the Folin– Ciocalteu method, and antibacterial activity using the minimum inhibitory concentration (MIC) method and the well diffusion method. The results indicate a rich content of total phenols 8919, 44 ± 26, 79 mg gallic acid equivalent (GAE)/L and high antioxidant activity of 100-fold diluted extracts (FRAP: 88.15 ± 4.54 mM Trolox equivalent ; DPPH: 67.29 %). Besides, the extracts showed good antimicrobial activity against all tested bacteria. The lowest MIC values (892 mg GAE/L) were observed against S. enterica, E. coli and E. faecalis, while the largest inhibition zone (>20 mm) was observed against S. aureus and L. monocytogenes.

green tea ; UAE ; phenolic profile ; antioxidant capacity ; antimicrobial activity

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