Sensory Nutrition and Bitterness and Astringency of Polyphenols.

Recent studies have demonstrated that the interaction of dietary constituents with taste and olfactory receptors and nociceptors expressed in the oral cavity, nasal cavity and gastrointestinal tract regulate homeostasis through activation of the neuroendocrine system. Polyphenols, of which 8000 have been identified to date, represent the greatest diversity of secondary metabolites in plants, most of which are bitter and some of them astringent. Epidemiological studies have shown that polyphenol intake contributes to maintaining and improving cardiovascular, cognitive and sensory health. However, because polyphenols have very low bioavailability, the mechanisms of their beneficial effects are unknown. In this review, we focused on the taste of polyphenols from the perspective of sensory nutrition, summarized the results of previous studies on their relationship with bioregulation and discussed their future potential.

Procyanidins and sensory nutrition; do procyanidins modulate homeostasis via astringent taste receptors?

Long-term intake of procyanidins has been suggested to reduce the risk of cardiovascular disease, dementia, and sensory function decline associated with aging. However, most of the ingested procyanidins are not absorbed and are excreted in the feces, so the mechanism of their beneficial impact is unknown. Procyanidins are the components of astringency in plant foods and their stimulation appears to be directly transmitted to the central nervous system via sensory nerves. Recent attention has been focused on the taste receptors expressed in the extra-oral gastrointestinal tract may regulate homeostasis via the neuroendocrine system. In this paper, we have reviewed recent findings on the relationship between the astringency of procyanidins and their bioregulatory effects.

Polyphenols in Inner Ear Neurobiology, Health and Disease: From Bench to Clinics.

There is substantial experimental and clinical interest in providing effective ways to both prevent and slow the onset of hearing loss. Auditory hair cells, which occur along the basilar membrane of the cochlea, often lose functionality due to age-related biological alterations, as well as from exposure to high decibel sounds affecting a diminished/damaged auditory sensitivity. Hearing loss is also seen to take place due to neuronal degeneration before or following hair cell destruction/loss. A strategy is necessary to protect hair cells and XIII cranial/auditory nerve cells prior to injury and throughout aging. Within this context, it was proposed that cochlea neural stem cells may be protected from such aging and environmental/noise insults via the ingestion of protective dietary supplements. Of particular importance is that these studies typically display a hormetic-like biphasic dose-response pattern that prevents the occurrence of auditory cell damage induced by various model chemical toxins, such as cisplatin. Likewise, the hormetic dose-response also enhances the occurrence of cochlear neural cell viability, proliferation, and differentiation. These findings are particularly important since they confirmed a strong dose dependency of the significant beneficial effects (which is biphasic), whilst having a low-dose beneficial response, whereas extensive exposures may become ineffective and/or potentially harmful. According to hormesis, phytochemicals including polyphenols exhibit biphasic dose-response effects activating low-dose antioxidant signaling pathways, resulting in the upregulation of vitagenes, a group of genes involved in preserving cellular homeostasis during stressful conditions. Modulation of the vitagene network through polyphenols increases cellular resilience mechanisms, thus impacting neurological disorder pathophysiology. Here, we aimed to explore polyphenols targeting the NF-E2-related factor 2 (Nrf2) pathway to neuroprotective and therapeutic strategies that can potentially reduce oxidative stress and inflammation, thus preventing auditory hair cell and XIII cranial/auditory nerve cell degeneration. Furthermore, we explored techniques to enhance their bioavailability and efficacy.

Exploring Novel Vitamin K Derivatives with Anti-SARS-CoV-2 Activity.

From our compound library of vitamin K derivatives, we found that some compounds exhibited anti-SARS-CoV-2 activity in VeroE6/TMPRSS2 cells. The common structure of these compounds was menaquinone-2 (MK-2) with either the m-methylphenyl or the 1-naphthyl group introduced at the end of the side chain. Therefore, new vitamin K derivatives having more potent anti-SARS-CoV-2 activity were explored by introducing various functional groups at the ω-position of the side chain. MK-2 derivatives with a purine moiety showed the most potent antiviral activity among the derivatives. We also found that their mechanism of action was the inhibition of RNA-dependent RNA polymerase (RdRp) of SARS-CoV-2. The chemical structures of our compounds were completely different from those of nucleic acid derivatives such as remdesivir and molnupiravir, clinically approved RdRp inhibitors for COVID-19 treatment, suggesting that our compounds may be effective against viruses resistant to these nucleic acid derivatives.

Hormesis defines the limits of lifespan.

This commentary provides a novel synthesis of how biological systems adapt to a broad spectrum of environmental and age-related stresses that are underlying causes of numerous degenerative diseases and debilitating effects of aging. It proposes that the most fundamental, evolutionary-based integrative strategy to sustain and protect health is based on the concept of hormesis. This concept integrates anti-oxidant, anti-inflammatory and cellular repair responses at all levels of biological organization (i.e., cell, organ and organism) within the framework of biphasic dose responses that describe the quantitative limits of biological plasticity in all cells and organisms from bacteria and plants to humans. A major feature of the hormetic concept is that low levels of biological, chemical, physical and psychological stress upregulate adaptive responses that not only precondition, repair and restore normal functions to damaged tissues/organs but modestly overcompensate, reducing ongoing background damage, thereby enhancing health beyond that in control groups, lacking the low level "beneficial" stress. Higher doses of such stress often become counterproductive and eventually harmful. Hormesis is active throughout the life-cycle and can be diminished by aging processes affecting the onset and severity of debilitating conditions/diseases, especially in elderly subjects. The most significant feature of the hormetic dose response is that the limits of biological plasticity for adaptive processes are less than twice that of control group responses, with most, at maximum, being 30-60 % greater than control group values. Yet, these modest increases can make the difference between health or disease and living or dying. The quantitative features of these adaptive hormetic dose responses are also independent of mechanism. These features of the hormetic dose response determine the capacity to which systems can adapt/be protected, the extent to which biological performance (e.g., memory, resistance to injury/disease, wound healing, hair growth or lifespan) can be enhanced/extended and the extent to which synergistic interactions may occur. Hormesis defines the quantitative rules within which adaptive processes operate and is central to evolution and biology and should become transformational for experimental concepts and study design strategies, public health practices and a vast range of therapeutic strategies and interventions.

Cinnamtannin A2, (-)-epicatechin tetramer, attenuates skeletal muscle wasting in disuse atrophy model mice induced by hindlimb suspension.

The impact of repeated administration of cinntamtannin A2 (A2, 25 µg/kg) on skeletal muscle disuse atrophy model mice induced by hindlimb suspension for 14 days was examined. In soleus, weight loss and a reduction in the average myofibre size with shifting to the smaller side of the peak were observed in the suspension-vehicle group, but A2 reduced these changes. Average myofibre size significantly increased in ground-A2 compared to ground-vehicle. A marked increase in the dephosphorylation of forkhead box O (FoxO) 3a by the suspension was reduced by A2. The phosphorylation of protein kinase B (Akt) and eukaryotic translation initiation factor 4E-binding protein (4EBP)-1 were significantly increased by the treatment of A2. In addition, a single dose of A2 increased dramatically in the 24-h excretion of catecholamines in urine. These results suggest that A2 administration results in sympathetic nerve activation and promotes hypertrophy while inhibiting the progress of disuse muscle atrophy.

Activation of transient receptor potential channels is involved in reactive oxygen species (ROS)-dependent regulation of blood flow by (-)-epicatechin tetramer cinnamtannin A2.

Intervention trials confirmed that blood flow-mediated dilatation increases significantly after intake of astringent (-)-epicatechin (EC) oligomers (procyanidins)-rich foods, but the mechanism remains unclear. We have previously found that procyanidins can activate the sympathetic nervous and subsequently increase blood flow. Here, we examined whether procyanidin-derived reactive oxygen species (ROS) activate transient receptor potential (TRP) channels in gastrointestinal sensory nerves and consequently induce sympathoexcitation. We evaluated the redox properties of EC and its tetramer cinntamtannin A2 (A2) at pH 5 or 7, mimicking plant vacuole or oral cavity/small intestine using a luminescent probe. At pH 5, A2 or EC showed O2·- scavenging ability, but they promoted O2·- generation at pH 7. We observed blood flow in rat cremaster arterioles using laser Doppler, a single oral dose of 10 µg/kg A2 markedly increased blood flow, while EC showed little activity. This change with A2 was significantly dampened by co-administration of adrenaline blocker, ROS scavenger N-acetyl-L-cysteine (NAC), TRP vanilloid 1, or ankyrin 1 antagonist. We also performed a docking simulation of EC or A2 with the binding site of a typical ligand for each TRP channel and calculated the respective binding affinities. The binding energies were notably higher for A2 than typical ligands, suggesting that A2 is less likely to bind to these sites. ROS produced at neutral pH following the orally administered A2 to the gastrointestinal tract could activate TRP channels, triggering sympathetic hyperactivation and causing hemodynamic changes.

Difference in endocrine and behavior between short-term single- and paired-housing mice in metabolic cage.

Metabolic cage housing which is exposed to a number of environmental stressors is often used in pharmacokinetic studies. In this study, we compared the difference in stress response between single- and paired-housing in metabolic cages by evaluating the alteration of urinary stress hormones and behavior. Mice were randomly divided into single- or paired-housing groups and placed in a metabolic cage with wire mesh. Their urine was collected every 24 h for consecutive 4 days to determine excreted catecholamine and corticosterone. The change in body weight was significantly decreased at 3 and 4 days in the single-housing group compared with that before the experiment, but not paired-housing group. The level of urinary catecholamines, such as noradrenaline, adrenaline, and their metabolite vanillylmandelic acid, was significantly increased in the single-housing compared with paired housing group and urinary corticosterone increased as well. Next, for the two similarly housed groups, we observed spontaneous behavior on the fourth day and conducted an elevated plus-maze test on the fifth day. Spontaneous behavior was not different between experimental groups. In the elevated plus-maze test, the proportion of time spent in the open arms was significantly prolonged in the paired-housing group compared to that of the single-housing group. Short-term social isolation stress loading in metabolic cages was suggested to exhibit endocrinological and behavioral changes in mice. To reduce such interference due to stress exposure, it was suggested to keep two mice in a metabolic cage.

Impact of cyanidin 3-O-glucoside on rat micro-and systemic circulation, possibly thorough angiogenesis.

Cyanidin 3-O-glucoside (C3G), an antioxidant, is one of the most abundant anthocyanin in plant foods. Intervention trials and subsequent meta-analyses have suggested that anthocyanins could reduce the risks of cardiovascular diseases. This study investigated hemodynamic alterations following a single intragastric dose of C3G by measuring blood flow in rat cremaster muscle arteriole for 60 min. Next, in excised aortas, we performed western blotting to measure the phosphorylation of Akt and endothelial nitric oxide synthase (eNOS). A single oral dose of C3G significantly increased blood flow soon after ingestion, and it was maintained throughout the experimental period. In addition, aortic Akt phosphorylation increased. Then, we examined the impact of repeated oral administrations of C3G for 14 days. The mean blood pressure was significantly reduced at 7 and 14 days after treatment, with a slight increase in aortic eNOS expression. Immunohistochemical analyses of the soleus showed that the level of CD31, an angiogenesis-marker protein, was significantly increased with C3G. These results suggested that an oral dose of C3G increased blood flow, which promoted angiogenesis within skeletal muscle, and consequently, blood pressure was reduced.

Hormetic response to B-type procyanidin ingestion involves stress-related neuromodulation via the gut-brain axis: Preclinical and clinical observations.

B-type procyanidins, a series of catechin oligomers, are among the most ingested polyphenols in the human diet. Results of meta-analyses have suggested that intake of B-type procyanidins reduces cardiovascular disease risk. Another recent focus has been on the effects of B-type procyanidins on central nervous system (CNS) function. Although long-term B-type procyanidin ingestion is linked to health benefits, a single oral intake has been reported to cause physiological alterations in circulation, metabolism, and the CNS. Comprehensive analyses of previous reports indicate an optimal mid-range dose for the hemodynamic effects of B-type procyanidins, with null responses at lower or higher doses, suggesting hormesis. Indeed, polyphenols, including B-type procyanidins, elicit hormetic responses in vitro, but animal and clinical studies are limited. Hormesis of hemodynamic and metabolic responses to B-type procyanidins was recently confirmed in animal studies, however, and our work has linked these effects to the CNS. Here, we evaluate the hormetic response elicited by B-type procyanidins, recontextualizing the results of intervention trials. In addition, we discuss the possibility that this hormetic response to B-type procyanidins arises via CNS neurotransmitter receptors. We have verified the direction of future research for B-type procyanidins in this review.

Can a Short-term Daily Oral Administration of Propolis Improve Muscle Fatigue and Recovery?

This study investigated the effect of 1-week oral administration of propolis on muscle fatigue and recovery after performing a fatigue task (total 100 maximal voluntary concentric knee extension repetitions). In this placebo-controlled, double-blind study, 18 young men consumed a formulation with high Brazilian green propolis dose (H-BGP), a formulation with low Brazilian green propolis dose, or a placebo, for 1 week before performing the fatigue task (an interval between each intervention: 1-2 weeks). Maximal voluntary contraction torque, central fatigue (voluntary activation and root mean square values of the surface electromyography amplitude), and peripheral fatigue (potentiated triplet torque) were assessed before, immediately after, and 2 minutes after the fatigue task. Maximal voluntary contraction torque decreased immediately after the fatigue task in all conditions (P<0.001); however, it recovered from immediately after to 2 minutes after the fatigue task only in the H-BGP condition (P<0.001). Furthermore, there was a significant decrease in voluntary activation (P<0.001) and root mean square values of the surface electromyography amplitude (P≤0.035) only in the placebo condition. No significant difference was observed in the time-course change in potentiated triplet torque between the conditions. These results suggest that oral administration of propolis promotes muscle fatigue recovery by reducing central fatigue.

Repeated Oral Administration of Flavan-3-ols Induces Browning in Mice Adipose Tissues through Sympathetic Nerve Activation.

We previously found increases in uncoupling protein (Ucp)-1 transcription in brown adipose tissue (BAT) of mice following a single oral dose of flavan 3-ol (FL)s, a fraction of catechins and procyanidins. It was confirmed that these changes were totally reduced by co-treatment of adrenaline blockers. According to these previous results, FLs possibly activate sympathetic nervous system (SNS). In this study, we confirmed the marked increase in urinary catecholamine (CA) s projecting SNS activity following a single dose of 50 mg/kg FLs. In addition, we examined the impact of the repeated administration of 50 mg/kg FLs for 14 days on adipose tissues in mice. In BAT, FLs tended to increase the level of Ucp-1 along with significant increase of thermogenic transcriptome factors expressions, such as peroxisome proliferator-activated receptor γ coactivator (PGC)-1α and PR domain-containing (PRDM)1. Expression of browning markers, CD137 and transmembrane protein (TMEM) 26, in addition to PGC-1α were increased in epididymal adipose (eWAT) by FLs. A multilocular morphology with cell size reduction was shown in the inguinal adipose (iWAT), together with increasing the level of Ucp-1 by FLs. These results exert that FLs induce browning in adipose, and this change is possibly produced by the activation of the SNS.

Impact of short-term oral dose of cinnamtannin A2, an (-)-epicatechin tetramer, on spatial memory and adult hippocampal neurogenesis in mouse.

Recent epidemiological and intervention studies have suggested that polyphenol-rich plant food consumption reduced the risk of cognitive decline. However, the findings were tentative and by no means definitive. In the present study, we examined the impact of short-term oral administration of cinnamtannin A2 (A2), an (-)-epicatechin tetramer, on adult hippocampal neurogenesis and cognitive function in mice. Mice received supplementation with vehicle (20% glycerol) or 100 µg/kg A2 for 10 days. Then, we conducted the open field test, the object location test, and the novel object test. In the open field test, the A2-treated group tended to spend more time in the center of the arena, compared to the vehicle-treated group. The A2-treated group spent significantly more time exploring objects placed in different locations, compared to the vehicle-treated group. There were no significant differences between groups in the object preference index or in the novel object test. In addition, A2 administration significantly increased the number of hippocampal bromodeoxyuridine-labeled cells in the dentate gyrus, but not in the CA1 or CA3 regions. These results suggested that short-term administration of A2 may impact spatial memory by enhancing neurogenesis in the dentate gyrus of adult mice.

Theaflavins decrease skeletal muscle wasting in disuse atrophy induced by hindlimb suspension in mice.

We previously found that a single dose of theaflavins induced skeletal muscle metabolic changes. In this study, we examined the effect of theaflavins on disuse muscle atrophy model mice by hindlimb suspension. Mice were assigned to 4 groups; ground-vehicle, ground-theaflavins, suspension-vehicle, and suspension-theaflavins, dosed with theaflavins (250 mg/kg/day) for 2 weeks. The peak of myotube size of cross sectional area was significantly moved to the smaller side in the suspension-vehicle group compared with the ground-vehicle group, and these shifts were significantly reduced by the treatment with theaflavins in both soleus and extensor digitorum longus. The level of phosphorylated eukaryotic translation initiation factor 4E-binding protein (4EBP)-1, located downstream of the Akt/mTOR pathway, was significantly different between suspension-vehicle and suspension-theaflavins in soleus. The ratio of forkhead box O (FoxO) 3a to phosphorylated FoxO3a significantly increased in soleus or tended to rise in extensor digitorum longus of suspension-vehicle group compared with ground-vehicle. In contrast, these changes were not observed in suspension-theaflavins group. These results suggested that theaflavins inhibited the progress of disuse muscle atrophy through modulation of protein metabolism.

Method for detecting hemodynamic alterations following a single gavage in rats.

It is known that administering a gavage to rodents evokes a cardiac reflex, due to gastrointestinal stimulation. Consequently, it is difficult to evaluate changes in hemodynamics after a single oral dose of a pungent or astringent, which alters the circulation by increasing sympathetic activity. In the present study, we developed a method for administering a gavage without significantly affecting hemodynamics measurements. We marked a gastric tube at 10 cm from the tip, to mark the distance from the oral cavity to the stomach body of Wistar male rats. Rats were intubated under urethane anesthesia.After 10-15 min of stabilization, we measured the mean blood pressure (MBP), heart rate (HR), and blood flow (BF) in the cremaster arteriole under two different conditions; condition 1: a pointed gastric tube, room temperature distilled water, and injected at normal speed (approximately 3 ml/min); condition 2: a rounded gastric tube, 37°C distilled water, and injection at 1.0 ml/min. Under condition 1, we observed striking hemodynamic alterations, due to the somatic afferent reflex. In contrast, under condition 2, these hemodynamic changes were nearly eliminated. In addition, we could clearly detect hemodynamic changes in rats after a single gavage treatment of pungent (capsaicin) or astringent (cinnamtannin A2). We observed transient increases in the HR and MBP soon after treatment with capsaicin. Moreover, cremasteric BF was elevated with cinnamtannin A2. These results confirmed the utility of the gavage method developed in this study.

Electrochemical Analysis of Coffee Extractions at Different Roasting Levels Using a Carbon Nanotube Electrode.

This study reports on the electrochemical analysis of coffee extractions at different roasting levels by using a carbon nanotube (CNT) electrode. The roasting levels, ranging from 1 (low) to 6 (high), were determined according to the roasting time after fixing the roasting temperature. Level 1 roasting resulted in light roasted beans and level 6 in dark roasted ones. Based on the roasting level, the concentration of chlorogenic acids, including 3-caffeoylquinic (3CQ), 4-caffeoylquinic (4CQ), and 5-caffeoylquinic (5CQ) acid, can be determined. Cyclic voltammetry (CV) experiments revealed that the reduction current at +0.27 V was proportional to the concentration of chlorogenic acids. High-performance liquid chromatography (HPLC) revealed an inverse correlation between the roasting level and chlorogenic acid amount. The total amounts of chlorogenic acids in coffee extractions determined by HPLC were in agreement with those obtained by CV using the CNT electrode at roasting levels 1 - 5. At level 6, the amount of chlorogenic acids determined by the current peak was larger than that detected by HPLC. As a result, the chlorogenic acid amount was overestimated in the CV experiment at +0.27 V, indicating that electrochemically active materials were generated at level 6. The CV profile showed that the reduction peak at +0.10 V increased with an increase in roasting level. Thus, the peak intensity at +0.10 V can be used to evaluate the roasting level even if the concentration or dilution conditions are provided.

Relationship between hemodynamic alteration and sympathetic nerve activation following a single oral dose of cinnamtannin A2.

We previously found that a single dose of B-type procyanidin mixture increase in skeletal muscle blood flow (BF). We compared BF changes following administration of (-)-epicatechin (EC, monomer) and the B-type procyanidins procyanidin B2 (B2, dimer), procyanidin C1 (C1, trimer), and cinnamtannin A2 (A2, tetramer). Each chemical was administered orally to rats, followed by BF measurement in cremaster arteriole for 60 min. About 10 and 100 µg/kg of B2 and C1 elicited BF increase, the effect was potent at 100 µg/kg. BF also increased significantly after administration of 10 µg/kg A2, but not with the administration at 100 µg/kg. EC yielded no BF changes. Co-treatment with the nonselective adrenaline blocker carvedilol attenuated the BF increase seen with 10 µg/kg A2 treatment. This outcome suggested the involvement of sympathetic nerve activation in the BF increase by this dose of A2. Co-treatment of 100 µg/kg A2 with the α2 blocker yohimbine exhibited an increase of BF significantly. The α2 adrenaline receptor in the vasomotor centre is an inhibitory receptor and it regulates hemodynamics. This result suggested that high doses of A2 did not alter BF because of activating the α2 adrenergic receptor. Phosphorylation of aortic endothelial nitric oxide synthase (eNOS) increased with 10 µg/kg A2 alone or co-treatment with 100 µg/kg A2 and yohimbine, but not with co-treatment of 10 µg/kg A2 and carvedilol or 100 µg/kg A2 alone. These results imply that A2 does not directly activate eNOS, but that shear stress from the increased BF might be associated with eNOS phosphorylation.

Effects of Cocoa Polyphenols and Dark Chocolate on Obese Adults: A Scoping Review.

Obesity remains a major public health problem due to its increasing prevalence. Natural products have become common as adjunct therapeutic agents for treating obesity and preventing metabolic diseases. Cocoa and its products are commonly consumed worldwide. Dark chocolate, a rich source of polyphenols, has received attention lately for its beneficial role in the management of obesity; however, conflicting results are still being reported. This scoping review aims to provide a comprehensive understanding of the existing literature on the relationship and effects of cocoa and dark chocolate intake among obese adults. We searched multiple databases for research investigating the consumption of cocoa and/or dark chocolate in managing obesity among adults. This review includes epidemiological and human studies that were published in English over the last 10 years. Our review of the current literature indicates that epidemiological and human trials with obese adults have shown inconsistent results, which may be due to the different populations of subjects, and different types of cocoa products and doses used for intervention. Studies among obese adults are mainly focusing on obese individuals with comorbidities, as such more studies are needed to elucidate the role of cocoa polyphenols in weight control and preventing the risk of chronic diseases among obese individuals without comorbidities as well as healthy individuals. Careful adjustment of confounding factors would be required. The effects of cocoa and dark chocolate intake on obese adults were discussed, and further research is warranted to identify the gaps.

Visualization of mechanical stress-mediated Ca2+ signaling in the gut using intravital imaging.

Mechanosensory systems have been implicated in the maintenance of gut homeostasis, but details on the related mechanisms are scarce. Recently, we generated a conditional Ca2+ biosensor yellow cameleon 3.60 (YC3.60)-expressing transgenic mouse model and established a five-dimensional (5D; x, y, z, time, and Ca2+) intravital imaging system for investigating lymphoid tissues and enteric epithelial cell responses. To validate this gut-sensing system, we visualized responses of enteric nervous system (ENS) cells in Nestin-Cre/YC3.60flox mice with specific YC3.60 expression. The ENS, including the myenteric (Auerbach's) and submucous (Meissner's) plexuses, could be visualized without staining in this mouse line, indicating that the probe produced sufficient fluorescent intensity. Furthermore, the myenteric plexus exhibited Ca2+ signaling during peristalsis without stimulation. Nerve endings on the surface of enteric epithelia also exhibited Ca2+ signaling without stimulation. Mechanical stress induced transient salient Ca2+ flux in the myenteric plexus and in enteric epithelial cells in the Nestin-Cre/YC3.60 and the CAG-Cre/YC3.60 lines, respectively. Furthermore, the potential TRPM7 inhibitors were shown to attenuate mechanical stress-mediated Ca2+ signaling. These data indicate that the present intravital imaging system can be used to visualize mechanosensory Ca2+ signaling in ENS cells and enteric epithelial cells.

Electrochemical Detection of Curcumin in Food with a Carbon Nanotube-Carboxymethylcellulose Electrode.

Herein, an electrochemical method is presented for the detection of curcumin in food using a carbon nanotube (CNT)-carboxymethylcellulose (CMC) electrode. The CNT-CMC electrode exhibited ideal characteristics for curcumin detection, namely, a high response current and adequate peak separation toward curcumin oxidation. Cyclic voltammetry revealed two oxidation peaks. In the first scan, only the irreversible peak (Peak I) was observed at a higher potential. In the second scan, the reversible redox peak pairs (Peaks II and II') appeared at lower potentials, and the potential of Peak I was decreased. Peak I corresponded to oxidation of the hydroxyl groups of the benzene ring to the catechol group via a phenoxy radical, while Peaks II and II' indicated the redox loop system of the generated catechol group. The current at Peak II was used to quantify the concentration of curcumin in the linear range of 1 - 48 µM and detection limit of 0.084 µM. The concentrations of curcumin determined by the CNT-CMC electrode in real food samples were consistent with those determined by high-performance liquid chromatography.