13 research outputs found
Transport of the Glucosamine-Derived Browning Product Fructosazine (Polyhydroxyalkylpyrazine) Across the Human Intestinal Caco‑2 Cell Monolayer: Role of the Hexose Transporters
The
transport mechanism of fructosazine, a glucosamine self-condensation
product, was investigated using a Caco-2 cell model. Fructosazine
transport was assessed by measuring the bidirectional permeability
coefficient across Caco-2 cells. The mechanism of transport was evaluated
using phlorizin, an inhibitor of sodium-dependent glucose cotransporters
(SGLT) 1 and 2, phloretin and quercetin, inhibitors of glucose transporters
(GLUT) 1 and 2, transcytosis inhibitor wortmannin, and gap junction
disruptor cytochalasin D. The role of hexose transporters was further
studied using downregulated or overexpressed cell lines. The apparent
permeability (<i>P</i><sub>a,b</sub>) of fructosazine was
1.30 ± 0.02 × 10<sup>–6</sup> cm/s. No significant
(<i>p</i> > 0.05) effect was observed in fructosazine
transport
by adding wortmannin and cytochalasin D. The presence of phlorizin,
phloretin, and quercetin decreased fructosazine transport. The downregulated
GLUT cells line was unable to transport fructosazine. In human intestinal
epithelial Caco-2 cells, GLUT1 or GLUT2 and SGLT are mainly responsible
for fructosazine transport
Retention time, MS and MS/MS data of the α-dicarbonyl compounds detected Mb-GlcN conjugates.
<p>Retention time, MS and MS/MS data of the α-dicarbonyl compounds detected Mb-GlcN conjugates.</p
Studies on the Formation of Maillard and Caramelization Products from Glucosamine Incubated at 37 °C
This experiment compared the in vitro
degradation of glucosamine
(GlcN), <i>N</i>-acetylglucosamine, and glucose in the presence
of NH<sub>3</sub> incubated at 37 °C in phosphate buffer from
0.5 to 12 days. The reactions were monitored with UV–vis absorption
and fluorescence emission spectroscopies, and the main products of
degradation, quinoxaline derivatives of α-dicarbonyl compounds
and condensation products, were determined using UHPLC-UV and Orbitrap
mass spectrometry. GlcN produced two major dicarbonyl compounds, glucosone
and 3-deoxyglucosone, ranging from 709 to 3245 mg/kg GlcN and from
272 to 4535 mg/kg GlcN, respectively. 3,4-Dideoxyglucosone-3-ene,
glyoxal, hydroxypyruvaldehyde, methylglyoxal, and diacetyl were also
detected in lower amounts compared to glucosone and 3-deoxyglucosone.
Several pyrazine condensation products resulting from the reaction
between dicarbonyls and GlcN were also identified. This study determined
that GlcN is a significantly unstable molecule producing a high level
of degradation products at 37 °C
Protein oxidation (carbonyl content) in Mb and Mb conjugated with GlcNAc, Glc and GlcN from 0 to 12 days.
<p>The results are mean ± standard deviation of three independent experiments. Data were fitted (except Mb-GlcN) with the non-linear fitting by GraphPad Prism software using following exponential equation: <i>y</i> = A(1-e<i><sup>-kt</sup></i>), where <i>y</i> is the product concentration, A is the initial value at <i>t</i><sub>0</sub>, <i>k</i> is the reaction rate, and <i>t</i> is time.</p
A deconvoluted ESI-MS spectra of Mb incubated at 37°C for various times in the presence of GlcNAc, Glc and GlcN.
<p>The experimental conditions were the same as those used to obtain the spectra in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0139022#pone.0139022.g001" target="_blank">Fig 1</a>. Inset spectrum (A) shows the spectrum of GlcN incubated for 12 days in the region of 7000–18000 Da.</p
UHPLC analyses of quinoxaline derivatives of α-dicarbonyl compounds produced from Mb-GlcN conjugates over time.
<p>(A) Chromatograms of (I) a reference quinoxaline mixture of glucosone (G), 3-deoxyglucosone (3-DG), glyoxal (GO), methylglyoxal (MGO) and diacetyl (DA). (II) Representative chromatogram of Mb-GlcN conjugate incubated for 1 d, derivatized with <i>o</i>-OPD and acquired by UHPLC with UV detection at 314 nm. Numbers indicate the peaks of the quinoxalines of (1) G, (2) unidentified, (3) 3-DG, (4) GO, (5) HPA, (6) 3,4- DGE, (7) MGO, (8) DA and a, b, c peaks corresponding to non-OPD derived GlcN condensation products.</p
Concentration of the major α-dicarbonyl compound produced during incubation of Mb in the presence of GlcN from 0 to 12 days.
<p>The values are represented as mean ± standard deviation (calculated from three independent trials). G, glucosone; 3-DG, 3-deoxyglucosone; GO, glyoxal; MGO, methylglyoxal; DA, diacetyl. Different letters within each α-dicarbonyl compound indicate statistical significant difference (<i>p</i> < 0.05).</p
Fructosazine, a Polyhydroxyalkylpyrazine with Antimicrobial Activity: Mechanism of Inhibition against Extremely Heat Resistant <i>Escherichia coli</i>
Fructosazine
is a polyhydroxyalkylpyrazine recently reported to
have antimicrobial activity against heat-resistant <i>Escherichia
coli</i> AW 1.7. This study investigated fructosazine’s
antimicrobial mechanism of action and compared it to that of riboflavin.
Fructosazine–acetic acid was effective in permeabilizing the
outer membrane based on an evaluation of bacterial membrane integrity
using 1-<i>N-</i>phenyl-1-naphthylamine and propidium iodide.
The uptake of fructosazine by <i>E. coli</i> was pH-dependent
with a greater uptake at pH 5 compared to pH 7 for all times throughout
16 h, except 2, 3, and 10 h. Fructosazine generates <sup>1</sup>O<sub>2</sub>, which is partially why it damages <i>E. coli</i>. DNA fragmentation was confirmed by fluorescence microscopy, and
the fructosazine–acetic acid was the second most intense treatment
after riboflavin–acetic acid. Electron microscopy revealed
membrane structural damage by fructosazine at pH 5 and 7. This study
provides evidence that fructosazine exerts antimicrobial action by
permeabilizing the cell membrane, damaging membrane integrity, and
fragmenting DNA
(A) Fluorescence emission spectra; (B) far-UV spectra analyses; (C) secondary structure composition; (D) maximum fluorescence intensity of Thioflavin T (λ = 482 nm).
<p>The data points all have SD bars, but some are illegible and lie within the symbols; (E) transmission electron micrographs of native Mb and Mb incubated in the presence of GlcN at specific time points.</p
MALDI-TOF/TOF mass spectra of Mb incubated at 37°C for various times in the presence of GlcNAc, Glc and GlcN.
<p>Glycation adducts are marked with a star, with the number of stars corresponding to the number of adducts. Inset spectrum (A) shows the spectrum of GlcN incubated for 12 days in the region of m/z 6000–18000.</p