Evaluation of in vitro antimicrobial activity of Camellia sinensis leaves collected at different time of harvest

Abstract

The amounts of chemicals in green tea depend on the time of harvest. In Korea, there is a tendency to harvest tea leaves to make green tea from around April 20 to the end of May. Therefore, we investigated the influence of harvest time of Camellia sinensis leaves on antimicrobial activity. The ethyl acetate and water fraction of ethanol extract from C. sinensis leaves collected every two weeks (April 30, May 14 and May 28, 2021) were tested against 4 Gram-positive and 3 Gram-negative bacteria and one yeast. Antimicrobial activity was screened for clear zone and minimal inhibition concentration (MIC) values determined by disc diffusion method. The ethyl acetate fraction was potentially effective against Methillin-resistant Staphylococcus aureus (MRSA), Bacillus cereus, Staphylococcus aureus and Salmonella typhimurium at all the collection dates. The results showed the diameter of clear zone was proportional to the concentration of tested fractions. The antimicrobial activity of tea leaves was different by collection dates, the quantitative difference was not big. The MIC value of ethyl acetate fraction of tea leaves for Bacillus cereus and B. subtilis was 0.5 mg/ml, on the other hand, the MIC value of the water fraction of tea leaves for B. subtilis, MRSA, Pseudomonas fluorescens and Salmonella typhimurium was 30.0 mg/ml, regardless of collection date. The antimicrobial properties of C. sinensis leaves encouraged an innovative potential application in agricultural, pharmaceutical and food fields.