Polyphenolic profiles, antioxidant capacity, and antibacterial activity of green tea, matcha tea, black tea, and yerba mate extracts
Kadrin Meremäe, Piret Raudsepp, Linda Rusalepp, Tiina Laun, Mati Roasto
Abstract
ABSTRACT Tea is widely consumed for its beneficial bioactive compounds with potential health benefits. This study investigated the polyphenolic profiles, total antioxidant capacity (TAC), and antibacterial activity of aqueous and 30% ethanolic extracts prepared from commercially available green tea, matcha tea, black tea, and yerba mate. The polyphenolic profiles were analyzed using HPLC-DAD-MS, with 28 compounds identified and semi-quantified based on extracted ion chromatogram areas. Total polyphenol content (TPC) was quantified as gallic acid equivalent using external calibration and UV chromatogram area at 280 nm. TAC was measured by the DPPH and Folin-Ciocalteu methods. Minimum inhibitory concentrations (MICs) against Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, and Campylobacter jejuni were determined using the broth microdilution method. Mate ethanolic extracts had the highest TPC (5.16 ± 0.02 mg GAE/mL), followed by green (4.68 ± 0.08 mg GAE/mL), black (4.26 ± 0.08 mg GAE/mL), and matcha tea extracts (3.55 ± 0.01 mg GAE/mL). The hierarchical dendrogram showed that mate extracts differed significantly ( p < 0.001) from the others, containing mainly chlorogenic acids and giving similar TAC, and MIC results for both aqueous and ethanolic extracts. Tea extracts exhibited the highest proportions of flavanols, mainly epigallocatechin, epicatechin gallate, and epigallocatechin gallate, which showed strong negative correlations ( r S = − 0.7 to − 0.8) with MICs against E. coli and strong positive correlations ( r S = 0.7 to 0.9) with TAC. S. aureus was the most susceptible to the studied plant extracts demonstrating the lowest MIC values ranging from 0.06 to 0.27 mg GAE/mL. Green tea extracts showed the strongest TAC and antibacterial activity. These findings highlight the potential of tea and mate extracts as natural antibacterial and antioxidant agents for food applications.