Polysaccharides
from functional foods have been proved to have
diverse bioactivities, but little is known about what exactly happens
to these polysaccharides after oral administration and even less about
the underlying mechanism of action. Taking the marker polysaccharide
(DOP) of Dendrobium officinale as an example, this
study aims to demonstrate the dynamic distribution and degradation
of orally dosed DOP in mice and in vitro using near-infrared fluorescence
imaging and a kind of chromatographic analysis. The results indicate
that (1) neither DOP nor fluorescence-labeled DOP (FDOP) was absorbed,
(2) both DOP and FDOP were undigested and were quickly degraded to
short-chain fatty acids in the large intestine, (3) DOP modulated
gut microbiota, which could be associated with DOP’s suppression
of 4T1 tumor growth in mice. All of these findings suggest that some
(maybe not all) bioactive polysaccharides share a common destiny:
indigestible and nonabsorbing, ends in modulating bioactivities-associated
gut microbiota.
Herein we describe a UPLC-FLD-based method for the quantification of the sialic acid content of red meat, using a synthetic neuraminic acid derivative as an internal standard. X-Gal-α-2,6-N-propionylneuraminic acid was synthesized via a chemoenzymatic pathway and its hydrolytic stability was characterized. Known quantities of this compound were incubated with samples of red meat under sialic acid-releasing conditions. The released sialic acids were derivatized, analyzed by UPLC-FLD, and the Neu5Ac/Neu5Gc content of the meat sample was determined by comparison with the internal standard. A number of red meats were analyzed by this method with the following results (Neu5Ac μg/g tissue, Neu5Gc μg/g tissue ± s.d.): pork (68 ± 3, 15.2 ± 0.7), beef (69 ± 8, 36 ± 5), lamb (46 ± 2, 33 ± 1), rabbit (59 ± 2, 0.4 ± 0.4), and hare (50 ± 4, 1 ± 1). We envisage that this methodology will find application in investigating the health effects of dietary Neu5Gc. Graphical abstract ᅟ.
A large portion of Maillard reaction products (MRPs) cannot be absorbed in the upper gut and therefore may be further decomposed and utilized by colonic microbiota (CM). This work reported the stability of UV-absorbent MRPs, fluorescent MRPs and peptide-bound N(ε)-(carboxymethyl)-lysine (CML) in high molecular weight (HMW, >10 kDa), medium molecular weight (MMW, 1−10 kDa), and low molecular weight (LMW, <1 kDa) gastrointestinal digests of glyoxalglycated casein in the presence of CM. Fluorescent MRPs showed high stability, whereas UV-absorbent MRPs may be partially decomposed. A higher depletion rate of CML was found in the LMW fraction (38.7%) than in the MMW (21.7%) and HMW (9.6%) fractions. The 16S rRNA sequencing results revealed both beneficial and detrimental changes in CM composition induced by the glycated fractions. Generation of short-chain and branched-chain fatty acids in fermentation solutions with glycated fractions was significantly suppressed compared with that in fermentation solution with unglycated digests. This work revealed the possible interplay between peptide-bound MRPs and CM.
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