Flavonols, the second most abundant flavonoids in green tea, exist mainly in the form of glycosides. Flavonols are known to have a variety of beneficial health effects; however, limited information is available on their fate in the digestive system. We investigated the digestive stability of flavonol aglycones and glycosides from green tea under simulated digestion and anaerobic human fecal fermentation. Green tea fractions rich in flavonol glycosides and aglycones, termed flavonol-glycoside-rich fraction (FLG) and flavonol-aglycone-rich fraction (FLA) hereafter, were obtained after treatment with cellulase and tannase, respectively. Kaempferol and its glycosides were found to be more stable in simulated gastric and intestinal fluids than the derivatives of quercetin and myricetin. Anaerobic human fecal fermentation with FLG and FLA increased the populations of Lactobacilli spp. and Bifidobacteria spp. and generated various organic acids, such as acetate, butyrate, propionate, and lactate, among which butyrate was produced in the highest amount. Our findings indicate that some stable polyphenols have higher bioaccessibilities in the gastrointestinal tract and that their health-modulating effects result from their interactions with microbes in the gut.
Common
buckwheat sprout (CBS) contains more flavone C-glycosides
(FCGs) and flavonol O-glycosides (FOGs)
than does common buckwheat seed. Both flavonoids in CBS are well known
for providing benefits to human health. However, they are relatively
less bioaccessible and more directly degradable to aglycone during
digestion than are multiglycosylated flavonoids. To overcome such
limitations, the water solubility and digestion stability of FCGs
and FOGs were enhanced by transglycosylation using cyclodextrin glycosyltransferase.
Gastric conditions had little effect on the stability of FCGs and
FOGs and their enzyme-modified compounds. In contrast, under intestinal
conditions, transglycosylated FCGs lost a glucose moiety and reverted
to their parent compounds before transglycosylation. Under colonic
fermentation using human fecal samples, the different profiles and
concentrations of short-chain fatty acids were suggested to be mainly
due to the presence of transglycosylated FCGs and FOGs. These findings
indicate that the process of transglycosylation changes the bioaccessibility
of flavonoids in CBS.
The use of probiotic starters can improve the sensory and health-promoting properties of fermented foods. In this study, we developed an anti-inflammatory probiotic starter, Limosilactobacillus reuteri EFEL6901, for use in kimchi fermentation. The EFEL6901 strain was safe for use in foods and was stable under human gastrointestinal conditions. In in vitro experiments, EFEL6901 cells adhered well to colonic epithelial cells and decreased nitric oxide production in lipopolysaccharide-induced macrophages. In in vivo experiments, oral administration of EFEL6901 to DSS-induced colitis mice models significantly alleviated the observed colitis symptoms, prevented body weight loss, lowered the disease activity index score, and prevented colon length shortening. Analysis of these results indicated that EFEL6901 played a probiotic role by preventing the overproduction of pro-inflammatory cytokines, improving gut barrier function, and up-regulating the concentrations of short-chain fatty acids. In addition, EFEL6901 made a fast growth in a simulated kimchi juice and it synthesized similar amounts of metabolites in nabak-kimchi comparable to a commercial kimchi. This study demonstrates that EFEL6901 can be used as a suitable kimchi starter to promote gut health and product quality.
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