ANALYSIS OF CATECHINS FROM GREEN AND BLACK TEA IN HUMANS - A SPECIFICAND SENSITIVE COLORIMETRIC ASSAY OF TOTAL CATECHINS IN BIOLOGICAL-FLUIDS

Catechins are a group of flavonoids widely occurring in fruits, wine a nd tea, which are strong antioxidants with demonstrated anticarcinogen ic effects in animal models. There is currently little knowledge on th e bioavailability of catechins due to a lack of suitable analytical me thods. Therefore a simple colorimetric assay was developed for the det ermination of the concentration of catechins in plasma. Following prec ipitation of proteins with methanol, tea flavonoids were accumulated b y solid phase adsorption to alumina. Reactions of adsorbed catechins w ith 4-dimethyl amino cinnamaldehyde under strong acidic conditions res ults in desorption and development of a highly selective coloured comp lex (lambda = 637 nm). The method is highly specific for catechins wit h equimolar responses for catechin, epicatechin, epigallocatechin, epi catechin gallate and epigallocatechin gallate. The detection limit in plasma is 0.05 mu mol/L and the within and between day variation was 1 .1% and 2.6%, respectively. Following consumption of a single dose of green tea, equivalent to six cups of tea, plasma levels of total catec hins of 2.36 +/- 0.55 mu mol/L (n = 5) were reached after 60 min. This novel method is a rapid and sensitive way to gain more insight in the bioavailability of catechins from tea, wine and foods.