Proanthocyanidin content in foods is largely underestimated in the literature data: An approach to quantification of the missing proanthocyanidins

Abstract

a b s t r a c tThe content of proanthocyanidins (PA) in foods is usually determined by HPLC analysis of aqueousorganic extracts. However, the appreciable amounts of PA that remain in the residues of extraction usually are not considered for analysis. Attempts to determine these non-extractable proanthocyanidins (NEPA) by enzymatic-chemical methods have obtained partial results. The general aim of this work was the estimation of the total content of PA, including both extractable PA (EPA) and NEPA in some foods included in the USDA database. A specific procedure based on depolymerization by HCl/BuOH treatment was used to quantify NEPA. The content of NEPA in analyzed samples ranged from 11 mg/100 g for pear to 6.7 g/100 g dry weight for red grape pomace. The results showed that literature data underestimate the actual content of PA in foods. NEPA may have a significant contribution to the healthy effects associated to PA-rich foods and diets.

Nonextractable polyphenols, usually ignored, are the major part of dietary polyphenols: A study on the Spanish diet

“…In the case of nonextractable PA, acid-catalyzed depolymerization in the presence of suitable nucleophilic reagents, such as benzylmercaptan, toluene-a-thiol (thiolysis) and phloroglucinol, or pectinolytic and cellulolytic enzymes to release PP from the food matrix, has been used as a preliminary step to HPLC analysis [21][22][23][24][25][26][27]. However, the PA contents reported in these studies were very low compared with the values reported after butanol/HCl/Fe extractions [28].…”

Non-extractable polyphenols, a major dietary antioxidant: occurrence, metabolic fate and health effects

“…Nevertheless, the results constitute evidence of an appreciable presence of NEPP in plant foods and of their contribution to total polyphenol intake. (31) Quince 48 (32) Banana 980 (SD 45)* (27) Apple pomace 18 -23 (33) Cranberry pomace 1685 (34) Cocoa powder 602 (SD 13) (35) Carob pod 180 (36) Hydrolysable phenolics Onion 410 (SD 20)* (37) Black olive 14 -40 (38) Apple 78 (SD 6) (29) Medlar 0·5 -1·0 (39) Mandarin 39 -107 (40) Acerola 390 (SD 10)* (41) Cashew apple 1210 (SD 70)* † (41) Black currant pomace…”

Extraction of cocoa proanthocyanidins and their fractionation by sequential centrifugal partition chromatography and gel permeation chromatography

“…The method by Porter, Hrstich, and Chan [16] and a modified one by Pérez-Jiménez, Arranz, and Saura-Calixto [17] were used during this study. For liquid cocoa extract suspected of having high reactivity, the following dilutions were made: 1:5, 1:10.…”