Simultaneous Determination of All Polyphenols in Vegetables, Fruits, and Teas

TLDR

Polyphenols, which have beneficial effects on health and occur ubiquitously in plant foods, are extremely diverse. The study developed a method to simultaneously determine all polyphenols in foodstuffs using HPLC and a photodiode array, building a library of retention times, spectra, and calibration curves for 100 standards. The method involved homogenizing food in liquid nitrogen, lyophilizing, extracting with 90 % methanol, and analyzing by HPLC without hydrolysis, then profiling polyphenols in 63 vegetables, fruits, and teas. The method achieved 68–92 % recovery, 1–9 % reproducibility, resolved polyphenols within 95 min, and allowed accurate, simultaneous determination of aglycons and glycosides without hydrolysis.

Abstract

Polyphenols, which have beneficial effects on health and occur ubiquitously in plant foods, are extremely diverse. We developed a method for simultaneously determining all the polyphenols in foodstuffs, using HPLC and a photodiode array to construct a library comprising retention times, spectra of aglycons, and respective calibration curves for 100 standard chemicals. The food was homogenized in liquid nitrogen, lyophilized, extracted with 90% methanol, and subjected to HPLC without hydrolysis. The recovery was 68-92%, and the variation in reproducibility ranged between 1 and 9%. The HPLC eluted polyphenols with good resolution within 95 min in the following order: simple polyphenols, catechins, anthocyanins, glycosides of flavones, flavonols, isoflavones and flavanones, their aglycons, anthraquinones, chalcones, and theaflavins. All the polyphenols in 63 vegetables, fruits, and teas were then examined in terms of content and class. The present method offers accuracy by avoiding the decomposition of polyphenols during hydrolysis, the ability to determine aglycons separately from glycosides, and information on simple polyphenol levels simultaneously.