Determination of antioxidant activity, rutin, quercetin, phenolic acids and trace elements in tea infusions: Influence of citric acid addition on extraction of metals

Abstract

Antioxidant activity of tea, content of bioactive compounds (rutin, quercetin, phenolic acids including: gallic, chlorogenic, protocatechuic, p-coumaric, caffeic, ferrulic, syringic and sinapic as well as other selected organic acids) and trace elements (Mn, selected as a metal playing a role in oxidative metabolism; Al; Cd; and Pb – the so-called heavy or noxious metals) were studied as these parameters greatly influence the quality of tea infusions. A number of different samples were tested including white, green, black and lemon-flavored teas, as well as the Red Lapacho tea. Antioxidant activity was measured using DPPH and ABTS tests, and a strong correlation between obtained results was observed. Infusions made from lemon teas packed in bags showed increased levels of rutin, quercetin and phenolic acids. Nevertheless, the positive effect of the increased level of phenolic compounds extracted is also connected with higher level of extracted noxious elements. Citric acid added to tea and herbal Red Lapacho infusions significantly increased Al, Cd, and Pb trace elements concentrations. Nevertheless, the infusions prepared from the lemon tea bags contained even the 10–70-fold higher content of these elements. On the other hand, addition of citric acid to tea infusions increased amount of extracted Mn only in black teas and Red Lapacho.