Identification and quantitation of phenolics from green beans by high-performance liquid chromatography

High-performance liquid chromatography with diode-array detection has been used for the separation and quantitation of phenolics from fresh and processed green beans. Whole beans, pods and seeds of green beans were studied separately Chromatographic profiles from pods were more complex than those found in seeds. Flavonol glycosides were confined to quercetin and kaempferol classes and they were typical of external parts of the fruit Flavan-3-ols monomers ((+) catechin and (-) epicatechin) as well as procyanidins structures were identified in pods and seeds. Chromatographic profiles from processed beans revealed a polyphenolic composition similar to those found in pod fresh green beans. The chromatographic method was carefully validated in regard to precision and accuracy. High reproducibility of peak area (RSD < 3%) and calibration slopes (RSD < 4%) was obtained. Recoveries between 94 - 104% revealed good accuracy for the overall method. Application to quantitative determination in a representative number of samples allowed good knowledge of the phenolic composition of green beans (Phaseolus vulgaris v. vulgaris).