Mee-Ra Rhyu

Umami taste characteristics of water extract of Doenjang, a Korean soybean paste: Low-molecular acidic peptides may be a possible clue to the taste

We investigated the taste characteristics of doenjang water extract (DWE) for component compounds that contribute to its taste. A 1% DWE solution elicited the highest umami taste ratings in a taste profile test. A 3% solution of DWE was used as substitute for 9.4% of monosodium glutamate in a taste soup base, and it masked the bitter taste of hydrolysed animal protein when mixed in solution. DWE was fractionated, based on molecular weights, and fraction IV (F-IV; 1000>MW⩾500) had the highest peptide contents and elicited the strongest umami taste. The acidic peptide fraction of F-IV elicited the strongest umami taste. The major bound-type amino acids in DWE, F-IV and the acidic peptide fraction were Glu and Asp. These data show that the umami taste characteristics were a result of the low molecular weight acidic peptides naturally produced during the fermentation of soybeans.

Authentication of Rice Using Near-Infrared Reflectance Spectroscopy

ABSTRACT The authentication of rice (Korean domestic rice vs. foreign rice) has been attempted using near-infrared spectroscopy (NIRS). Two sample sets (n1 = 280 and n2 = 200) were used to obtain calibration equations and the spectral regions used for this study were 500–600 nm, 700–900nm, and 980–2,498 nm. Modified partial least square (MPLS) regression was used to develop the prediction model. The standard error of cross validation (SECV) and the r2 were 0.165 and 0.91 respectively for 1st calibration set and 0.165 and 0.93 for 2nd calibration set respectively. The results of the independent validation (n3 = 80) showed that all of 80 samples were identified correctly. Even though authentication of rice was performed successfully using NIRS, the calibration statistics in this study showed that further effort is needed for implementation of NIRS for authentication of rice for industry purposes.

Artepillin C, a Major Ingredient of Brazilian Propolis, Induces a Pungent Taste by Activating TRPA1 Channels

Brazilian green propolis is a popular health supplement because of its various biological properties. The ethanol extract of Brazilian green propolis (EEBP) is characteristic for its herb-like smell and unique pungent taste. However, the ingredients responsible for its pungency have not yet been identified. This study provides the first evidence that artepillin C is the main pungent ingredient in EEBP and that it potently activates human transient receptor potential ankyrin 1 (TRPA1) channels. EEBP was fractionated using column chromatography with a step gradient elution of an ethanol-water solution, and the fractions having the pungent taste were determined by sensory tests. HPLC analysis revealed that the pungent fraction was composed primarily of artepillin C, a prenylated derivative of cinnamic acid. Artepillin C was also identified as the pungent compound of EEBP by organoleptic examiners. Furthermore, the effects of artepillin C and other cinnamic acids found in EEBP on TRPA1 channels were examined by calcium imaging and plate reader-based assays in human TRPA1-expressing cells to investigate the molecular mechanisms underlying their pungent tastes. Artepillin C and baccharin activated the TRPA1 channel strongly, whereas drupanin caused a slight activation and p-coumaric acid showed no activation. Because the EC50 values of artepillin C, baccharin, and allyl isothiocyanate were 1.8 µM, 15.5 µM, and 6.2 µM, respectively, artepillin C was more potent than the typical TRPA1 agonist allyl isothiocyanate. These findings strongly indicate that artepillin C is the main pungent ingredient in EEBP and stimulates a pungent taste by activating TRPA1 channels.

The TRPA1 agonist, methyl syringate suppresses food intake and gastric emptying.

Transient receptor potential channel ankryn 1 (TRPA1) expressed in the gastrointestinal tract is associated with gastric motility, gastric emptying, and food intake. In this study, we investigated the effects of methyl syringate, a specific and selective TRPA1 agonist, on food intake, gastric emptying, and gut hormone levels in imprinting control region (ICR) mice. The administration of methyl syringate suppressed cumulative food intake and gastric emptying. In addition, treatment with ruthenium red (RR), a general cation channel blocker, and HC-030031, a selective TRPA1 antagonist, inhibited methyl syringate-induced reduction of food intake and delayed gastric emptying in ICR mice. Methyl syringate also increased plasma peptide YY (PYY) levels, but not glucagon-like peptide-1 (GLP-1) levels. The elevation in PYY was blocked by treatment with RR and HC-030031. The present findings indicate that methyl syringate regulates food intake and gastric emptying through a TRPA1-mediated pathway and, by extension, can contribute to weight suppression.

Radix angelica elicits both nitric oxide-dependent and calcium influx-mediated relaxation in rat aorta.

This study examined the vascular relaxation produced by Radix Angelica (AG; Dong Quai) and its possible mechanisms in isolated rat aortic rings precontracted with norepinephrine. The butanolic fraction (AgBt) of the crude extract of AG causes gradual endothelium-independent relaxation, which was unaffected by five different potassium channel inhibitors. AgBt attenuated the CaCl2-induced vasoconstriction in high-potassium depolarized medium; this required less than one-tenth the concentration needed to elicit vascular relaxation. An aqueous fraction (AgDw) of the crude extract induced transient acute relaxation, which was virtually abolished by endothelial ablation and pretreatment with L-NNA. L-Arginine fully reversed the action of L-NNA. Methylene blue and atropine significantly attenuated the relaxation, but indomethacin did not. Ferulic acid, the main active component in AG, relaxed both endothelium-intact and -denuded rings, while L-NNA, methylene blue, or atropine did not modify the relaxation. Ferulic acid also did not attenuate the CaCl2-induced contraction in high-potassium depolarized medium. In conclusion, Radix Angelica leads to both endothelium-dependent and -independent relaxation of isolated rat aorta. Increased formation of NO might contribute to the endothelium-mediated relaxation, while inhibition of the calcium influx might be an important mechanism in direct smooth muscle relaxation. A substance other than ferulic acid might create these effects.

Nitric oxide-mediated endothelium-dependent relaxation of rat thoracic aorta induced by aqueous extract of red rice fermented with Monascus ruber

Vasodilatory effects of aqueous extract of red rice fermented with Monascus ruber IFO32318 were examined on the isolated rat aorta. The water phase of fermented rice with Monascus (WP/FRM, 0.1-10 mg/ml) caused a transient relaxation of the endothelium-intact rat aorta precontracted with norepinephrine (NE, 300 nM). The WP/FRM-induced relaxation was abolished by removal of endothelium or in the presence of N(G)-nitro-L-arginine (L-NNA, 10 microM), a nitric oxide (NO) synthase inhibitor. Neither atropine, a muscarinic receptor antagonist (10 microM), nor indomethacin, a cyclooxygenase inhibitor (10 microM), altered the WP/FRM-induced endothelium-dependent relaxation. gamma-Aminobutyric acid (GABA), one of the principle components of the extract, did not affect the muscle tension of the aorta with intact endothelium. In addition, WP/FRM increased the production of NO in primary cultured endothelial cells from human umbilical vein. The enhanced production of NO by WP/FRM was diminished by pretreatment with L-NNA (10 microM). In conclusion, WP/FRM induces relaxation of rat aorta by releasing NO from endothelium. There seem to be some unknown factor(s) other than acetylcholine (Ach) and GABA, in the aqueous extract of red rice, which stimulate vascular endothelial cells to produce and/or release NO leading to endothelium-dependent relaxation by WP/FRM.

Umami-bitter interactions: the suppression of bitterness by umami peptides via human bitter taste receptor.

Taste-taste interactions often showed in human psychophysical studies. Considering that each tastant in foodstuffs individually stimulates its responsible gustatory systems to elicit relevant taste modalities, taste-taste interaction should be performed in taste receptor cell-based assay. While umami substances have been proposed to suppress the bitterness of various chemicals in human sensory evaluation, the bitter-umami interaction has not been explored in bitter taste receptors, TAS2Rs. We investigated umami-bitter taste interactions by presenting umami peptides with bitter substance (salicin) on Ca(2+)-flux signaling assay using hTAS2R16-expressing cells. Five representative umami peptides (Glu-Asp, Glu-Glu, Glu-Ser, Asp-Glu-Ser, and Glu-Gly-Ser) derived from soybean markedly attenuated the salicin-induced intracellular calcium influx in a time-dependent manner, respectively, while Gly-Gly, a tasteless peptide did not. The efficacies of Glu-Glu suppressing salicin-induced activation of hTAS2R16 were higher than that of probenecid, a specific antagonist of hTAS2R16. According to Ca(2+)-flux signaling assay using the mixtures of salicin and umami peptides, all five umami peptides suppressed salicin-induced intracellular calcium influx in a noncompetitive manner. These results may provide evidence that umami peptides suppress bitter taste via bitter taste receptor(s). This is the first report which defines the interaction between bitter and umami taste in taste receptor level.

Hypoxia-inducible factor 1α activates and is inhibited by unoccupied estrogen receptor β

Previously, we showed that hypoxia induces ligand‐independent estrogen receptor (ER)α activation. In this study, we found that hypoxia activated the ERβ‐mediated transcriptional response in HEK293 cells in the absence of estrogen. ERβ transactivation was induced by the expression of the hypoxia‐inducible factor 1α (HIF‐1α) under normoxia. ERβ interacted with HIF‐1α, and SRC1 and CBP potentiated the effect of HIF‐1α on ERβ‐mediated transcription. We then examined the effect of ERβ on HIF1‐α transactivation. Surprisingly, ERβ attenuated the transcriptional activity of HIF‐1α, as measured by HRE‐driven reporter gene expression and hypoxic induction of VEGF mRNA in HEK293 cells. Taken together, these data show that HIF‐1α activates ERβ‐mediated transcription in the absence of a ligand, and ERβ inhibits HIF‐1α‐mediated transcription.

Estrogen activities and the cellular effects of natural progesterone from wild yam extract in mcf-7 human breast cancer cells.

We studied the estrogenic activity and cellular effect of wild yam extract in MCF-7 human breast cancer cells. The extract increased the activity of the progesterone receptor and pS2 genes at the mRNA levels in human breast cancer MCF-7 cells, although the effects were not as prominent as those of 17beta-estradiol (E(2)). Western blot analysis showed that the level of estrogen receptor alpha protein was down-regulated after treatment with E(2) or wild yam extract. Wild yam extract also inhibited proliferation of MCF-7 cells. These data indicate that wild yam extract acts as a weak phytoestrogen and protects against proliferation in human breast carcinoma MCF-7 cells.

Methyl syringate, a low-molecular-weight phenolic ester, as an activator of the chemosensory ion channel TRPA1.

Transient receptor potential channel ankryn 1 (TRPA1) and transient receptor potential channel vanilloid 1 (TRPV1) are members of the TRP superfamily of structurally related, nonselective cation channels and are often coexpressed in sensory neurons. Extracts of the first leaves of Kalopanax pictus Nakai (Araliaceae) have been shown to activate hTRPA1 and hTRPV1. Therefore, the effects of six commercially available chemicals (methyl syringate, coniferyl alcohol, protocatechuic acid, hederacoside C, α-hederin, and eleutheroside B) found in K. pictus were investigated on cultured cells expressing hTRPA1 and hTRPV1. Of the six compounds, methyl syringate selectively activated hTRPA1 (EC50 = 507.4 μM), but not hTRPV1. Although methyl syringate had a higher EC50 compared with allyl isothiocyanate (EC50 = 7.4 μM) and cinnamaldehyde (EC50 = 22.2 μM), the present study provides evidence that methyl syringate from K. pictus is a specific and selective activator of hTRPA1.