Conteúdo de miricetina, quercetina e kaempferol em chás comercializados no Brasil

Abstract

The myricetin, quercetin and kaempferol contents of a brand of "ban-chá", two brands of green tea and four brands of black tea were determined. Three lots of each brand were analysed in duplicate by high performance liquid chromatography. Quercetin (2.5-3.4 mg/g of dry leaf) predominated in all samples, followed by kaempferol (1.0-2.0 mg/g of dry leaf), with the exception of one sample, in which kaempferol and myricetin had the same levels. There was variation between different types of tea and even between brands of the same type of tea. Myricetin (trace-1.9 mg/g of dry leaf) was the flavonol, that varied the most and was present at lower levels in black tea. Other teas widely consumed in Brazil were also investigated. Myricetin was not found in teas of fruits (apple and strawberry) and herbs (anise, camomile, lemon grass, peppermint, boldo, maté, green maté), but quercetin was found in four teas (camomile, boldo, strawberry, green maté) and kaempferol, in two teas (boldo, green maté) at concentrations of 0.4 to 2.5 mg/g and 0.4 to 2.6 mg/g of dry leaf, respectively. It is concluded that these teas are sources of flavonols in the Brazilian diet, although at levels lower than those of green and black tea.