11 research outputs found
Thresholds and IC<sub>50</sub> values of 6-methoxyflavanones for inhibition of hTAS2R39 responses towards 200 ÎĽM ECG and 1.7 mM denatonium benzoate.
<p>n.b., no blocking.</p><p>n.d., not determined.</p
Thresholds and IC<sub>50</sub> values of 6-methoxyflavanones for inhibition of hTAS2R14 responses towards 640 ÎĽM ECG and 70 ÎĽM genistein.
<p>n.b., no blocking.</p><p>n.d., not determined.</p
Chemical structures of hTAS2R39 agonist epicatechin gallate (ECG) (A), investigated flavanones (residues specified in Table 1) (B) and hTAS2R39 agonist denatonium benzoate (C).
<p>The commonly applied ring-nomenclature for flavonoids (A-, B-, and C-ring) is shown in the general structure formula for flavanones.</p
Inhibition of response of 640 μM ECG (---) on hTAS2R14 (induced (•), non-induced (○)) by 4′-fluoro-6-methoxyflavanone (6) after simultaneous addition (n = 2) (A) and stepwise addition (n = 3) (B). Data are presented as mean ±SEM of n separate experiments conducted in duplicate.
<p>Inhibition of response of 640 μM ECG (---) on hTAS2R14 (induced (•), non-induced (○)) by 4′-fluoro-6-methoxyflavanone (6) after simultaneous addition (n = 2) (A) and stepwise addition (n = 3) (B). Data are presented as mean ±SEM of n separate experiments conducted in duplicate.</p
Fluorescent counts of ECG-induced calcium responses in cells expressing hTAS2R39 (induced) and non-expressing hTAS2R39 (non-induced).
<p><b>A</b>: Simultaneous addition of agonist (ECG 200 μM) and antagonist (4′-fluoro-6-methoxyflavanone (<b>6</b>) 16 μM) (□) versus the signal elicited by ECG (antagonist replaced by buffer, final concentration ECG 200 μM) (◊). Non-induced cells: ECG 200 μM and 4′-fluoro-6-methoxyflavanone (<b>6</b>) 16 μM (○) and ECG 200 μM (Δ). <b>B</b>: Stepwise addition of first antagonist (arrow “1<sup>st</sup> addition”), and then agonist (arrow “2<sup>nd</sup> addition”) (1<sup>st</sup> 6-methoxyflavanone (<b>11</b>) 500 μM, 2<sup>nd</sup> ECG 200 μM) (□)) versus agonist (1<sup>st</sup> buffer, 2<sup>nd</sup> ECG 200 μM) (◊). Non-induced cells: 1<sup>st</sup> 6-methoxyflavanone (<b>11</b>) 500 μM, 2<sup>nd</sup> ECG 200 μM (○) versus 1<sup>st</sup> buffer, 2<sup>nd</sup> ECG 200 μM (Δ).</p
Isoproterenol responses upon application with buffer, 4′-fluoro-6-methoxyflavanone (6), 6,3′-dimethoxyflavanone (3), and 6-methoxyflavanone (11).
<p>Data are presented as mean ±SEM of a representative experiment conducted in quadruplicate. n.s., not significant.</p
Dose-response curves for epicatechin gallate (ECG) (•) (n = 2) (A) and denatonium benzoate (•) (n = 2) (B) on hTAS2R39, and their modification by increasing 4′-fluoro-6-methoxyflavanone (6) concentrations (○ 50 μM, Δ 100 μM, □ 200 μM).
<p>Antagonist and agonist were added in the stepwise way. Data are presented as mean ±SEM of n separate experiments conducted in duplicate. Wash-out experiments (n = 2) (C). Cells were stimulated with 200 μM ECG in the absence (open bars) and in the presence (filled bars) of 100 μM 4′-fluoro-6-methoxyflavanone (6), or 500 μM 6,3′-dimethoxyflavanone (3), or 500 μM 6-methoxyflavanone (11), washed with Tyrode's buffer, and again stimulated with 200 μM ECG (hatched bars; control: grey bar). Antagonist and agonist were added in the stepwise way. Data are presented as mean ±SEM of n separate experiments conducted in quadruplicate. Significance of signal reduction is indicated by *** (p≤0.001), ** (p≤0.01), and n.s. (not significant, p>0.05).</p
Bitter Taste Receptor Activation by Flavonoids and Isoflavonoids: Modeled Structural Requirements for Activation of hTAS2R14 and hTAS2R39
Many flavonoids and isoflavonoids
have an undesirable bitter taste,
which hampers their use as food bioactives. The aim of this study
was to investigate the effect of a large set of structurally similar
(iso)Âflavonoids on the activation of bitter receptors hTAS2R14 and
hTAS2R39 and to predict their structural requirements to activate
these receptors. In total, 68 compounds activated hTAS2R14 and 70
compounds activated hTAS2R39, among which 58 ligands were overlapping.
Their activation threshold values varied over a range of 3 log units
between 0.12 and 500 ÎĽM. Ligand-based 2D-fingerprint and 3D-pharmacophore
models were created to detect structure–activity relationships.
The 2D models demonstrated excellent predictive power in identifying
bitter (iso)Âflavonoids and discrimination from inactive ones. The
structural characteristics for an (iso)Âflavonoid to activate hTAS2R14
(or hTAS2R39) were determined by 3D-pharmacophore models to be composed
of two (or three) hydrogen bond donor sites, one hydrogen bond acceptor
site, and two aromatic ring structures, of which one had to be hydrophobic.
The additional hydrogen bond donor feature for hTAS2R39 ligands indicated
the possible presence of another complementary acceptor site in the
binding pocket, compared to hTAS2R14. Hydrophobic interaction of the
aromatic feature with the binding site might be of higher importance
in hTAS2R14 than in hTAS2R39. Together, this might explain why OH-rich
compounds showed different behaviors on the two bitter receptors.
The combination of in vitro data and different in silico methods created
a good insight in activation of hTAS2R14 and hTAS2R39 by (iso)Âflavonoids
and provided a powerful tool in the prediction of their potential
bitterness. By understanding the “bitter motif”, introduction
of bitter taste in functional foods enriched in (iso)Âflavonoid bioactives
might be avoided
EC<sub>50</sub> values of ECG and denatonium benzoate in the presence of various concentrations of 4′-fluoro-6-methoxyflavanone (<b>6</b>) on hTAS2R39.
<p>EC<sub>50</sub> values of ECG and denatonium benzoate in the presence of various concentrations of 4′-fluoro-6-methoxyflavanone (<b>6</b>) on hTAS2R39.</p
Inhibition of response of 1.7(---) on hTAS2R39 (induced (•), non-induced (○)) by 4′-fluoro-6-methoxyflavanone (6) after simultaneous addition (n = 4) (A) and stepwise addition (n = 4) (B).
<p>Data are presented as mean ±SEM of n separate experiments conducted in duplicate.</p