Quantification of catechin and epicatechin in foods by enzymatic‑spectrophotometric method with tyrosinase

Abstract

Catechin and epicatechin are important phenolic compounds found mainly in tea leaves, cocoa beans, and in the peels and seeds of fruits. The reliable detection of these compounds by spectrophotometry is limited by the interference with substances that absorb light at similar wavelengths; thus, an effective alternative is to detect the oxidation products of these compounds at more specific wavelengths. This study aimed to develop an analytical method to quantify total catechin and epicatechin in some food samples (cocoa beans, guarana powder, apples, and tea leaves) by enzymatic oxidation with tyrosinase. The samples were extracted in an ultrasonic bath and the purified extracts were oxidized with tyrosinase solution. The quinones formed in the reaction were detected by spectrophotometry. The method was selective and presented linearity between 1.21 and 7.26 mg g−1, limit of detection of 0.48 mg g−1, and limit of quantification of 1.61 mg g−1. The accuracy of the proposed method was reasonable, with recoveries between 84.3 and 90.7% in the fortified matrices. High precision was observed, with low coefficients of variation for repeatability (3.17 to 3.68%) and intermediate precision (3.27%). In cocoa beans, the total catechin and epicatechin level was 1.65 mg g−1 (3.58 mg g−1). The successful application of the method was also demonstrated in guarana powder. Therefore, the method can be applicable for spectrophotometric analysis of catechin and epicatechin in samples containing above 1.61 mg g−1 of these compounds.