LC-DAD-ESI-MS/MS characterization of phenolic constituents in Turkish black tea: Effect of infusion time and temperature.

The influence of different infusion times and temperatures on phenolic, antioxidant, and color properties of black teas (Camellia sinensis L.) was investigated in the present study. The teas were prepared using infusion times of 3, 6, and 10min at 80 and 100°C. Liquid chromatography coupled to diode array detection and electrospray ionization tandem mass spectrometry (LC-DAD-ESI-MS/MS), whereby the two purine alkaloids were detected using positive ESI, and the other 33 phenolic compounds were detected using negative ESI. A total of 35 phenolic compounds were identified and quantified in the tea infusions, with the most abundant being gallic acid, (-)-epicatechin-gallate, 4-p-coumaroylquinic acid, quercetin-3-O-galactosyl-rhamnosyl-glucoside, kaempferol-3-O-glucosyl-rhamnosyl-glucoside, theaflavin, and theobromine. The antioxidant capacity of the tea infusions was determined using two different methods: DPPH (2,2-diphenyl-1-picryl hydrazyl) and ABTS (2,2'-azino-bis-3-ethyl-benzothiazoline-6-sulfonic acid) assays. DPPH and the ABTS values varied largely among the tea preparations. The increment in infusion times and temperature led to increase in the tea's antioxidant capacities.