Focusing on 17 constituents, the polyphenol profiles of juices freshly made from various dessert (n = 4) and cider apple cultivars (n = 7) as well as commercially available apple juices (n = 24) were investigated using high-performance liquid chromatography-photodiode array detection (HPLC-DAD) and (HPLC)-electrospray ionization-tandem mass spectrometry (ESI(neg)-MS/MS) analyses. Significant differences in the total polyphenol content as well as the profiles of the apple cultivars under study were observed. For dessert apples the total polyphenol content ranged from 154 to 178 mg/L, whereas for 'old' German cider apple cultivars 261-970 mg/L were determined. Boskoop showed the highest (970 mg/L) and Granny Smith the lowest (154 mg/L) polyphenol content of the freshly prepared samples under study. Hydroxycinnamic acids, with chlorogenic acid as dominating constituent, ranged from 57 to 68 mg/L as well as from 134-593 mg/L in juices made from dessert apples and that from cider apples, respectively. Dessert apple juices showed lower contents of dihydrochalcones (10-35 mg/L) and flavan-3-ols (50-95 mg/L) compared to that of cider apples (34-171 mg/L and 70-393 mg/L, respectively). Quercetin and its derivatives were found from 0.4-4 mg/L and 0.4-27 mg/L in juices made from dessert apples and that of cider apples, respectively. Compared with freshly made juices, lower contents of polyphenols were determined in the commercial samples under study. Amounts ranging from 110-459 mg/L, dominated by chlorogenic acid with concentrations from 53-217 mg/L, were determined. Information about cultivar-typical apple polyphenol content and profile is important for bioactivity studies and, consequently, essential for the development of consumer-relevant products with particular nutritional functionalities.

Polyphenols are secondary plant compounds showing anticarcinogenic effects both in vitro and in animal experiments and may thus reduce the risk of colorectal cancer in man. The identification of polyphenol metabolites formed via their passage through the small intestine of healthy ileostomy subjects after apple juice consumption is presented. Identification and quantification of polyphenols and their metabolites were performed using HPLC-DAD as well as HPLC-ESI-MS/MS. Total procyanidin content (TPA) was measured, and additionally the mean degree of polymerization (DPm) of the procyanidins was determined in the apple juice and ileostomy effluents. As products of polyphenol metabolism, D-(-)-quinic acid and methyl esters of caffeic acid and p-coumaric acid are liberated from the corresponding hydroxycinnamic acid esters. 1-Caffeoylquinic acid and 3-caffeoylquinic acid were determined as products of isomerization. Phloretin 2'-O-glucoside (phloridzin) and phloretin 2'-O-xyloglucoside were metabolized into the corresponding aglycons phloretin and phloretin 2'-O-glucuronide and all were found in the ileostomy effluent. Ninety percent of the consumed procyanidins were recovered in the ileostomy effluent and therefore would reach the colon under physiologic circumstances. The DP m was reduced (DP m of apple juice=5.7) and varied depending on the time point of excretion. The gastrointestinal passage seems to play an important role in the colonic availability of apple polyphenols.

The aim of our studies was to determine the amount of polyphenols reaching the colon after oral intake of apple juice and blueberries. After a polyphenol-free diet healthy ileostomy volunteers consumed a polyphenol-rich cloudy apple juice while others consumed anthocyanin-rich blueberries. Ileostomy effluent was collected and polyphenols were identified using HPLC-DAD as well as HPLC-ESI-MS/MS; quantification was performed with HPLC-DAD. Most of the orally administered apple polyphenols were absorbed from or metabolized in the small intestine. Between 0 and 33% of the oral dose was recovered in the ileostomy bags with a maximum of excretion after 2 h. A higher amount of the blueberry anthocyanins under study (up to 85%, depending on the sugar moiety) were determined in the ileostomy bags and therefore would reach the colon under physiological circumstances. Such structure-related availability has to be considered when polyphenols are used in model systems to study potential preventive effects in colorectal diseases.

The findings relating to the absorption, metabolism, and systemic availability of polyphenols in vivo should contribute to our understanding of their biological effects, and the characterization of newly formed metabolites should facilitate further studies.