Quantification of uronic acids in tea polysaccharide conjugates and their antioxidant properties.

A technique of high-performance liquid chromatography (HPLC) was described for the measurement of total uronic acids in tea polysaccharide conjugates. This method was applied to polysaccharide conjugate extracts obtained from green tea after most of the components that produce interference were removed. The preliminary extraction process was according to the procedure of isolation of polysaccharide conjugates. The uronic acid content of different polysaccharide conjugate fractions was quantified by HPLC on a Sugar-Pak I column with a 1.0 x 10(-)(4) mol x L(-)(1) calcium disodium ethylenediaminetetraacetic acid solution as the mobile phase and refractive index detection. The validation study showed high recoveries (>97.0%) and low coefficients of variance (<3.0%). The minimum detectable limit concentration of uronic acid was 10 microg x mL(-)(1). The analysis of a standard range of galacturonic acid concentrations (100-4000 microg x mL(-)(1)) yielded linear results. The use of the method on different polysaccharide conjugate fraction samples confirmed its effectiveness. With the high content of uronic acids in polysaccharide conjugates, the stronger reactive oxygen species scavenging activities were found.