Human intestinal hydrolysis of phenol glycosides -: a study with quercetin and p-nitrophenol glycosides using ileostomy fluid

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 (37 degrees C for 0, 0.5, 1, 2, 4, 6, 8, 10 and 24 h) with ileostomy fluids from three different donors. The glycosides, i.e. beta-D-glucopyranosides, beta-D-galactopyrano sides, alpha-L-arabinofuranosides, beta-D-xylopyranosides and alpha-L-rhamnopyranosides as well as the liberated aglycones were identified by HPLC-DAD and HPLC-ESI-MS/MS. Among the quercetin glycosides under study, the 3-O-beta-D-glucopyranoside showed with 0.22 mu mol/h the highest hydrolysis rate, followed by the 3-O-beta-D-galactopyranoside, the 3-O-beta-D-xylopyranoside and the 3-O-alpha-L-arabinofuranoside (0.04 and each 0.03 mu mol/h, respectively). Quercetin 3-O-alpha-L-rhamnopyranoside was found to be stable for the entire incubation period. Using quercetin 3-O-beta-D-glueopyrano side as a representative example, linear hydrolysis rate was observed from 75 to 2500 mu L ileostomy fluid corresponding to its microflora content (log 0.68 up to 21.9 colony forming units). Studies performed in the presence of antibiotics did not reveal any hydrolysis. The p-nitrophenol glycosides were hydrolyzed faster than the corresponding quercetin glycosides. The hydrolysis rate decreased from the beta-D-glucopyranoside (0.41 mu mol/h), to the beta-D-galactopyranoside (0.21 mu mol/h), the beta-D-xylopyrano side (0.12 mu mol/h), the alpha-L-arabinofuranoside (0.09 mu mol/h) to the alpha-L-rhamnopyranoside (0.06 mu mol/h). These results demonstrate that the human ileal hydrolysis of phenol glycosides depends on the sugar and the aglycon structure as well as the microflora.