Effect of brewing conditions on polyphenols in the dark tea (Camellia sinensis L.) infusions: content, composition and antioxidant activities

Abstract

The study was the first to investigate the content and composition along with the antioxidant activities of polyphenols in the dark tea infusions. The effect of brewing conditions on total polyphenolic contents (TPC) in dark tea infusions was conducted by response surface methodology (RSM), and the composition of polyphenolic compounds was investigated using ultraperformance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOF/MS), and DPPH and ABTS assay were used to evaluate the antioxidant activity of dark tea. Results showed that brewing at water/tea radio 50 : 1 mL/g, temperature 92 °C and time 27 min was the best condition to obtain the highest TPC (3.90 mg/mL). The composition of polyphenolic compounds in the infusions included 11 catechins and derivatives, 19 flavones and flavone glycosides, and 1 phenolic acid, and the concentrations of epigallocatechin gallate (91.32 mg/L) and epicatechin-3-O-gallate (23.10 mg/L) was the highest among the quantitative compounds. Moreover, the dark tea had good scavenging activities on DPPH (IC50 = 9.94 μg/mL) and ABTS (IC50 = 17.26 μg/mL) free radicals.