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

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.

Phenolic profile of hazelnut (Corylus Avellana L.) leaves cultivars grown in Portugal

“…Antioxidants from plants, namely phenolic compounds [1][2][3], can be used in order to preserve food, for organoleptic and nutritional qualities, and also for medicinal purposes [4,5].…”

Profiling methods for the determination of phenolic compounds in foods and dietary supplements

“…Compromises in extraction and separation will affect both identification and quantification. Tables 1, 2, 3, 4 present 14 profiling methods for phenolic compounds that have been selected from the literature of the last 15 years [18][19][20][21][22][23][24][25][26][27][28][29][30][31]. This is not meant to be a comprehensive list.…”

“…In some cases, the methods were directed at a limited number of food materials, but could be readily modified for application to a greater breadth of materials than originally described [19,20,22,25,27]. In recent years, however, methods have appeared that were designed to cover a wide range of compounds in any type of food material [21,23,24,26,28,29] or as metabolite profiling methods [30,31]. For these methods, liquid chromatography (LC) is the method of choice for separation and diode array detection) and mass spectrometry (MS) detection are the detection methods of choice.…”

“…Other researchers used LC-DAD for characterization of phenolic compounds without hydrolysis [19][20][21]24]. However, positive identification and quantification required the availability of appropriate glycosylated standards or a second chromatogram after hydrolysis of the sample.…”

“…However, positive identification and quantification required the availability of appropriate glycosylated standards or a second chromatogram after hydrolysis of the sample. Sakakibara et al [24] developed an LC-DAD method for the identification of "all" polyphenols (over 100 compounds from 11 phenolic subclasses) in vegetables, fruits, and teas, based on retention times and UV/vis spectra. Quantification was based on acid hydrolysis and external aglycone standards.…”