Synergistic, antagonistic and additive interactions of green tea polyphenols

Abstract

Green tea is a natural source of polyphenols where their catechins and flavonols are the major components. Their antioxidant activities are the most important biological effect and often the object of study. DPPH (2,2-diphenyl-1-picryl-hydrazyl) radical assay has been carried out to measure the individual scavenging activities expressed as percentage of DPPH inhibition for each tea polyphenol, and (−)-gallocatechin gallate (GCG) (74.04 ± 0.38 %) and (−)-epigallocatechin gallate (EGCG) (69.51 ± 0.27 %) were the most active compounds. Synergistic, antagonistic and additive interactions among catechin derivatives as well as combined with green tea extract have been analyzed, where GCG and EGCG provided most of the synergistic effects. Flavonols such as quercetin (54.61 ± 0.21 %) and kaempferol (24.06 ± 0.02 %) also showed free radicals’ scavenging activity. Interactions between flavonols and individual catechins as well as their mixtures in the tea extract have been investigated. The results suggested that the presence of tea flavonols in tea extract provided additive interactions and the tea catechins were responsible for synergism in green tea. This work can be the starting point of the research about supplemented green tea from its own catechins to increase the total antioxidant capacity of the green tea.