Factorial design-assisted spectrophotometric methods for the determination of total catechins in green tea extract via reaction with MBTH. Application to commercial tablet

Green tea extract (GTE) is a supplement derived from the green tea plant which aids in weight loss along with other innumerable health. New analytical methods for determining GTE via its catechins using a design-assisted spectrophotometric methodologies are provided. The procedures are based on the formation of orange-colored products that are detectable at 473 or 455 nm, respectively, when catechins react with MBTH in the presence of FeCl 3 (method I) or K 2 S 2 O 8 (method II). Critical parameters were optimized using design of experiments (DOE). The absorbance-concentration plots were rectilinear over the ranges 4.0–20.0 or 4.0–40.0 µg cm −3 with limits of detection 0.393 or 0.493 µg cm −3 for methods I & II, respectively. Our methods were applied to pure catechins in GTE, namely (-)-epicatechin and (-)-epigallocatechin gallate. Moreover, the proposed methods were perfectly applied to the analysis of GTE in a commercial tablet. Good agreement between the collected data and those of the reported approach demonstrating that there were no significant variations. According to International Council for Harmonization (ICH) Guidelines, the procedures were validated. Graphical abstract