3 research outputs found
Different Phenolic Compounds Activate Distinct Human Bitter Taste Receptors
Bitterness is a major sensory attribute of several common
foods
and beverages rich in polyphenol compounds. These compounds are reported
as very important for health as chemopreventive compounds, but they
are also known to taste bitter. In this work, the activation of the
human bitter taste receptors, TAS2Rs, by six polyphenol compounds
was analyzed. The compounds chosen are present in a wide range of
plant-derived foods and beverages, namely, red wine, beer, tea, and
chocolate. Pentagalloylglucose (PGG) is a hydrolyzable tannin, (ā)-epicatechin
is a precursor of condensed tannins, procyanidin dimer B3 and trimer
C2 belong to the condensed tannins, and malvidin-3-glucoside and cyanidin-3-glucoside
are anthocyanins. The results show that the different compounds activate
different combinations of the ā¼25 TAS2Rs. (ā)-Epicatechin
activated three receptors, TAS2R4, TAS2R5, and TAS2R39, whereas only
two receptors, TAS2R5 and TAS2R39, responded to PGG. In contrast,
malvidin-3-glucoside and procyanidin trimer stimulated only one receptor,
TAS2R7 and TAS2R5, respectively. Notably, tannins are the first natural
agonists found for TAS2R5 that display high potency only toward this
receptor. The catechol and/or galloyl groups appear to be important
structural determinants that mediate the interaction of these polyphenolic
compounds with TAS2R5. Overall, the EC<sub>50</sub> values obtained
for the different compounds vary 100-fold, with the lowest values
for PGG and malvidin-3-glucoside compounds, suggesting that they could
be significant polyphenols responsible for the bitterness of fruits,
vegetables, and derived products even if they are present in very
low concentrations
Molecular Interaction Between Salivary Proteins and Food Tannins
Polyphenols interaction with salivary
proteins (SP) has been related with organoleptic features such as
astringency. The aim of this work was to study the interaction between
some human SP and tannins through two spectroscopic techniques, fluorescence
quenching, and saturation transfer difference-nuclear magnetic resonance
(STD-NMR). Generally, the results showed a significant interaction
between SP and both condensed tannins and ellagitannins. Herein, STD-NMR
proved to be a useful tool to map tanninsā epitopes of binding,
while fluorescence quenching allowed one to discriminate binding affinities.
Ellagitannins showed the greatest binding constants values (<i>K</i><sub>SV</sub> from 20.1 to 94.1 mM<sup>ā1</sup>; <i>K</i><sub>A</sub> from 0.7 to 8.3 mM<sup>ā1</sup>) in
comparison with procyanidins (<i>K</i><sub>SV</sub> from
5.4 to 40.0 mM<sup>ā1</sup>; <i>K</i><sub>A</sub> from 1.1 to 2.7 mM<sup>ā1</sup>). In fact, punicalagin was
the tannin that demonstrated the highest affinity for all three SP.
Regarding SP, P-B peptide was the one with higher affinity for ellagitannins.
On the other hand, cystatins showed in general the lower <i>K</i><sub>SV</sub> and <i>K</i><sub>A</sub> values. In the case
of condensed tannins, statherin was the SP with the highest affinity,
contrasting with the other two SP. Altogether, these results are evidence
that the distinct SP present in the oral cavity have different abilities
to interact with food tannins class
New AnthocyanināHuman Salivary Protein Complexes
The
interaction between phenolic compounds and salivary proteins
is considered the basis of the poorly understood phenomenon of astringency.
Furthermore, this interaction is an important factor in relation to
their bioavailability. In this work, interactions between anthocyanin
and human salivary protein fraction were studied by mass spectrometry
(MALDI-TOF-MS and FIA-ESI-MS) and saturation-transfer difference (STD)
NMR spectroscopy. Anthocyanins were able to interact with saliva proteins.
The dissociation constant (<i>K</i><sub>D</sub>) between
malvidin 3-glucoside and salivary proline-rich proteins was 1.92 mM
for the hemiketal form (pH 3.4) and 1.83 mM for the flavylium cation
(pH 1.0). New soluble complexes between these salivary proteins and
malvidin 3-glucoside were identified for the first time