Colorectal tumor risks could be reduced by polyphenol-rich diets that inhibit cell growth. Here, apple polyphenols were studied for effects on the survival of colon adenoma (LT97) and carcinoma-derived (HT29) cell lines. Three apple extracts (AEs) from harvest years 2002-2004 were isolated (AE02, AE03, and AE04) and fermented in vitro with human fecal flora. Extracts and fermentation products were analyzed for polyphenols with HPLC. The cells were treated with AEs (0-850 microg/mL) or fermented AEs (F-AEs, 0-9%), and survival was measured by DNA staining. All AEs contained high amounts of polyphenols (311-534 mg/g) and reduced cell survival (in LT97 > HT29). AE03 was most potent, possibly because it contained more quercetin compounds. Fermentation of AEs resulted in an increase of short chain fatty acids, and polyphenols were degraded. The F-AEs were approximately 3-fold less bioactive than the corresponding AEs, pointing to a loss of chemoprotective properties through fermentation.

Apples represent a major dietary source of antioxidative polyphenols. Their metabolic conversion by the gut microflora might generate products that protect the intestine against oxidative damage. We studied the antioxidant effectiveness of supernatants of fermented apple juice extracts (F-AEs, 6 and 24 h fermentation) and of selected phenolic degradation products, identified by HPLC-DAD-ESI-MS. Cell free antioxidant capacity of unfermented apple juice extracts (AEs) was decreased after fermentation by 30-50%. In the human colon carcinoma cell line Caco-2, F-AEs (containing <0.5% of original AE-phenolics) decreased the reactive oxygen species (ROS) level more efficiently than the F-blank (fermented without AE) but were less effective than the respective AEs. Similarly, antioxidant effectiveness of individual degradation products was lower compared to respective AE constituents. Glutathione level was slightly increased and oxidative DNA damage slightly decreased by fermented AE03, rich in quercetin glycosides. In conclusion, F-AEs/degradation products exhibit antioxidant activity in colon cells but to a lesser extent than the respective unfermented AEs/constituents.

In order to study the influence of sugar moiety, aglycon structure and microflora concentration on the human ileal hydrolysis of phenol glycosides, various quercetin and p-nitrophenol glycosides were incubated under anaerobic conditions (378C for 0, 0. IntroductionThe flavonol quercetin is one of the most prevalent and thoroughly studied dietary flavonoids. It is present in fruits, vegetables and beverages, mostly bound to one or more sugar molecules [1,2], and is regarded to exhibit chemopreventive properties [3][4][5][6]. The predominant type of glycoside varies among the plant species. For instance, onion contains predominantly quercetin glucosides, while in apple mainly galactosides, rhamnosides and arabinosides have been found [7,8]. Concerning the bioavailability of quercetin there is evidence from the literature that the sugar moiety is of importance [1,[9][10][11]. The first step in the metabolic pathway of quercetin is the hydrolysis of the sugar

Health benefits associated with diets rich in anthocyanins are ascribed to multilevel biological activities including antioxidative and anti-inflammatory effects. The present study addresses lipoxygenase inhibition as a mechanism by which anthocyanins may exert health promoting effects. The inhibitory potential of delphinidin (Dp), cyanidin (Cy), peonidin (Pn), and malvidin (Mv) glycosides, i.e., 3-O-glucosides, 3-O-galactosides, and 3-O-arabinosides as well as their aglycons was analyzed by using soybean lipoxygenase-1 and human neutrophil granulocyte 5-lipoxygenase. The determined IC(50) values comprised a wide range, i.e., from the sub-microM level until practically no effect of inhibition (Mv and its glycosides). With IC(50) values of 0.43 and 0.49 microM Dp 3-O-glucoside (Dp3glc) and Dp 3-O-galactoside (Dp3gal) were found to be the most effective soybean lipoxygenase-1 inhibitors; their strong inhibitory potential was also reflected by the IC(50) values determined for these anthocyanins in the 5-lipoxygenase inhibition exhibiting 2.15 and 6.9 microM, respectively. As to the mechanism of inhibition, experiments carried out with lipoxygenase-1 revealed the uncompetitive type. Considering the powerful inhibitory properties of Dp glycosides in relation to their currently known availability in human metabolism, in vivo prevention of inflammatory diseases by these anthocyanins could be envisaged.

In order to study the human intestinal transit and metabolism of D-galacturonic acid and amidated pectin a number of model experiments were carried out. Both substrates were incubated under aerobic conditions at 37 degrees C using saliva (2 min) and simulated gastric juice (4 h). Under anaerobic conditions the substrates were incubated at 37 degrees C using human ileostomy and colostomy fluids, each obtained from three different donors, for 10 and for 24 h, respectively. D-Galacturonic acid, SCFA (acetic acid, propionic acid, and butyric acid), as well as methanol were analyzed photometrically after carbazole reaction, GC-flame ionization detection (GC-FID), and headspace solid-phase microextraction GC/MS (HS-SPME-GC/MS), respectively. D-Galacturonic acid and amidated pectin were found to be stable during incubations with saliva and simulated gastric juice, whereas both substrates underwent degradation in the course of human ileostomy and colostomy fluid incubations. D-Galacturonic acid was practically completely decomposed within 10 h and SCFA, with acetic acid as the major representative, were formed up to 98% of the incubated substrate in colostomy effluent. The amidated pectin was only degraded in part, revealing stable amounts of 22-35% and 3-17% in ileostomy (after 10 h) and colostomy fluid (after 24 h), respectively. SCFA were generated up to 59% of the applied amidated pectin. In parallel, 19-60% and 52-67% of the available methyl ester groups were cleaved in the course of incubations with ileostomy and colostomy fluids, respectively. The results demonstrate for the first time that D-galacturonic acid and amidated pectin are stable in human saliva and simulated gastric juice. The degradation of both compounds during incubation with ileostomy effluent is highlighted, providing evidence for a considerable metabolic potential of the small intestine.