The Influence of Galactooligosaccharide Addition to a Plant Sterol-Enriched Beverage upon Plant Sterol Colonic Metabolization: A Clinical Trial

The consumption of milk-based fruit beverages enriched with plant sterols (PSs) has previously showed a cholesterol-lowering effect in postmenopausal women [1]. The addition of galactooligosaccharides (GOSs) to these kinds of beverages could enhance their functionalities; however, their effect on the colonic metabolism of PSs is yet unknown. To shed light on this, a randomized, double blind, crossover study with postmenopausal women (n = 42, 58 ± 4 years) was carried out with the aim of evaluating GOS effects on PS colonic metabolism. Volunteers consumed 250 mL of a PS-enriched beverage (1%, w/v) daily with or without GOSs (1.8%, w/v) for 6 weeks, and feces samples were collected before and at the end of each intervention period. The contents of PS (sitosterol, sitostanol, campesterol, campestanol and stigmasterol) and its metabolites (ethylcoprostanol from sitosterol, methylcoprostanone from campesterol and ethylcoprostenol from stigmasterol) were measured by CG-MS [2]. Statistically significant increments (p < 0.05) in sterol concentrations (mg/g freeze-dry feces) were observed after the consumption of any of the beverages (with vs. without GOS addition) expressed as median (percentile 25; 75%): 8.29 (1.49; 17.27) vs. 10.79 (2.14; 19.30) for sitosterol, 12.95 (2.65; 20.66) vs. 14.47 (4.91; 21.56) for ethylcoprostanol, 2.84 (1.34; 4.91) vs. 3.16 (1.27; 4.80) for sitostanol, 1.09 (0.34; 2.03) vs. 1.41 (0.47; 2.11) for campesterol, 0.15 (0.03; 0.40) vs. 0.18 (0.03; 0.45) for methylcoprostanone, 0.46 (0.20; 0.80) vs. 0.44 (0.23; 0.82) for campestanol and 0.07 (0.00; 0.19) vs. 0.09 (0.02; 0.23) for stigmasterol. No significant changes were observed in ethylcoprostenol contents after the consumption of the beverage with or without GOSs (0.01 (−0.01; 0.02) vs. 0.002 (−0.02; 0.02)). No significant differences in net increments were observed between beverages. These results indicate that the presence of GOSs in PS-enriched beverages does not modify the colonic biotransformation of PSs.

The Effect of Formulation of Curcuminoids on Their Metabolism by Human Colonic Microbiota

Turmeric (Curcuma longa L.) is the only edible plant recognized as a dietary source of curcuminoids, among which curcumin, demethoxycurcumin (DMC) and bis-demethoxycurcumin (Bis-DMC) are the most representative ones. Curcumin shows a very low systemic bioavailability and for this reason, several technologies have been adopted to improve it. These technologies generally improve curcuminoid absorption in the small intestine, however, no data are available about the effect of curcuminoid formulation on colonic biotransformation. The present study aims at investigating the human colonic metabolism of curcuminoids, prepared with two different technologies, using an in vitro model. Unformulated curcuminoid and lecithin-curcuminoid botanical extracts were fermented using an in vitro fecal model and colonic catabolites were identified and quantified by uHPLC-MSn. Native compounds, mainly curcumin, DMC and bis-DMC, were metabolized by colonic microbiota within the 24-h incubation. The degradation of curcuminoids led to the formation of specific curcuminoid metabolites, among which higher concentrations of bis(demethyl)-tetrahydrocurcumin and bis(demethyl)-hexahydrocurcumin were found after lecithin-extract fermentation compared to the concentration detected after unformulated extract. In conclusion, both curcumin-based botanical extracts can be considered important sources of curcuminoids, although the lecithin-formulated extract led to a higher production of curcuminoid catabolites. Moreover, a new curcuminoid catabolite, namely bis(demethyl)-hexahydrocurcumin, has been putatively identified, opening new perspectives in the investigation of curcuminoid bioavailability and their potential metabolite bioactivity.

Dietary fibre, functions by modulating the entero-hepatic circulation

Dietary Fibre (DF) is not an essential component of the diet but a modulator of the absorption and colonic metabolism of nutrients and xenobiotics along the small and large intestine. In the colon DF stimulates the bacterial flora, bacterial mass and metabolism, thereby influencing the entero-hepatic circulation (EHC) and faecal output. This modulation is dependent upon the amount and physical state of DF intake.