Optimization of a Quantitative Method for the Determination of Catechins in Fruits and Legumes

Abstract

Catechins are found in many foods of plant origin. In vivo and in vitro studies have shown their potential health effects. The quantification of catechins has been optimized in three model foods: apples, black grapes, and canned kidney beans. Catechins [(+)-catechin, (−)-epicatechin, (−)-epigallocatechin, (−)-epicatechin gallate, and (−)-epigallocatechin gallate] were separated with gradient reversed phase HPLC and quantified by UV (270 nm) or fluorescence (280/310 nm excitation/emission) detection in series. Type (ethanol, methanol, or acetone) and concentration (40−100% in water) of extraction solvent influenced catechin yield, whereas extraction time (10−60 min) did not. Adequate extraction was attained with 60−100% methanol for apples and grapes and with 40−80% methanol for beans. Recovery (>94%), within-run repeatability (1−5%), between-run reproducibility (3−9%), and detection limits (0.1−3.9 mg/kg of fresh apple or 0.01−0.29 μg/mL extract) were satisfactory. With this method 40 solid food samples a day can be analyzed, without the need for sample cleanup. Keywords: Catechins; fruits; legumes; extraction; analytical techniques; fluorescence