A reevaluation of the peroxynitrite scavenging activity of some dietary phenolics

Leaves of Allium cepa and Xylopia aethiopica fruits as potent sources of natural antioxidant for stabilization of viscera FISH oil during accelerated storage

The present study investigated the antioxidant activities of methanolic extracts of two local plants and their capacities to preserve the quality of viscera fish oil during storage. The total phenolic, total flavonoids and tannins contents were analyzed by colorimetry, the preliminary antioxidant tests done and identification of phenolic compounds by HPLC-DAD (Diode Array Detector) and ESI-MS. After these evaluation, the plant extracts were added in viscera fish oil at concentration 200-1000 ppm. The oxidative stability of these fish oil samples was evaluated by measuring their qualities indices during 16 days at 70 °C. Here, oils were collected at the day 0, 4, 8, 12 and 16. The total phenolic, flavonoids and tannins contents in Xylopia aethiopica fruits were 15.62 g Eq acid galic/100g of dry extract, 10.85 mg Eq quercetin/100g of dry extract and 0.79 mg Eq cathechin/100 mg of dry extract. Those of Allium cepa leaves were 6.85 g Eq acid galic/100g of dry extract, 1.50 mg Eq quercetin/100g of dry extract and 0.11 mg Eq cathechin/100 mg of dry extract. All the methanolic extracts exhibited antioxidant activity. The results recorded after FRAP assay revealed the low IC50 (12.87 mg/mL) in Allium cepa extract compared to that of Xylopia aethiopica extract (44.90 mg/mL). These local plants contain many classes of phenolic compounds and they can be used in oil and fat industries as alternative of synthetic antioxidants.

Predicting the effects of in-vitro digestion in the bioactivity and bioaccessibility of antioxidant compounds extracted from chestnut shells by supercritical fluid extraction - A metabolomic approach

Chestnut (Castanea sativa) shells (CS) are an undervalued antioxidant-rich by-product. This study explores the impact of in-vitro digestion on the bioaccessibility, bioactivity, and metabolic profile of CS extract prepared by Supercritical Fluid Extraction, aiming its valorization for nutraceutical applications. The results demonstrated significantly (p < 0.05) lower phenolic concentrations retained after digestion (38.57 µg gallic acid equivalents/mg dry weight (DW)), reaching 30% of bioaccessibility. The CS extract showed antioxidant/antiradical, hypoglycemic, and neuroprotective properties after in-vitro digestion, along with upmodulating effects on antioxidant enzymes activities and protection against lipid peroxidation. The metabolic profile screened by LC-ESI-LTQ-Orbitrap-MS proved the biotransformation of complex phenolic acids, flavonoids, and tannins present in the undigested extract (45.78 µg/mg DW of total phenolic concentration) into hydroxybenzoic, phenylpropanoic, and phenylacetic acids upon digestion (35.54 µg/mg DW). These findings sustain the valorization of CS extract as a promising nutraceutical ingredient, delivering polyphenols with proven bioactivity even after in-vitro digestion.

Simulated Gastrointestinal Digestion of Chestnut (Castanea sativa Mill.) Shell Extract Prepared by Subcritical Water Extraction: Bioaccessibility, Bioactivity, and Intestinal Permeability by In Vitro Assays

Chestnut shells (CSs) are an appealing source of bioactive molecules, and constitute a popular research topic. This study explores the effects of in vitro gastrointestinal digestion and intestinal permeability on the bioaccessibility and bioactivity of polyphenols from CS extract prepared by subcritical water extraction (SWE). The results unveiled higher phenolic concentrations retained after gastric and intestinal digestion. The bioaccessibility and antioxidant/antiradical properties were enhanced in the following order: oral < gastric ≤ intestinal digests, attaining 40% of the maximum bioaccessibility. Ellagic acid was the main polyphenol in the digested and undigested extract, while pyrogallol-protocatechuic acid derivative was only quantified in the digests. The CS extract revealed potential mild hypoglycemic (<25%) and neuroprotective (<75%) properties before and after in vitro digestion, along with upmodulating the antioxidant enzymes' activities and downregulating the lipid peroxidation. The intestinal permeation of ellagic acid achieved 22.89% after 240 min. This study highlighted the efficacy of the CS extract on the delivery of polyphenols, sustaining its promising use as nutraceutical ingredient.

Ferulic acid-loaded nanocapsules: Evaluation of mucosal interaction, safety and antioxidant activity in human mononucleated cells

Ferulic acid (FA) is a phenolic compound that has antioxidant, anti-inflammatory and anticarcinogenic properties besides presenting cytoprotective activity. It has limited oral bioavailability what is a challenge to its therapeutic application. In this way, this investigation aimed to develop FA-loaded nanocapsule suspensions (NC-FA) prepared with ethylcellulose and evaluate their in vitro release profile, mucoadhesion and irritation potential; scavenging capacity, cytotoxicity, cytoprotection and genoprotection against hydrogen peroxide-induced damage in hMNC (human Mononucleated Cells) culture. The nanocapsules presented physicochemical characteristics compatible with colloidal systems (NC-FA: 112 ± 3 nm; NC-B (without FA): 107 ± 3 nm; PdI < 0.2; Span<2.0 and negative zeta potential). In addition, the nanoparticulate system promoted the FA controlled release, increasing the half-life twice through the in vitro dialysis method. NC-FA and NC-B were able to interact with mucin, which is an indicative of mucoadhesive properties and the association of FA with nanocapsules showed decreased irritation by HET-CAM method. Besides, the NC-FA did not present cytotoxicity in hMNC and improved the ATBS radical scavenging capacity. Besides, it prevented, treated and reversed oxidative conditions in a H₂O₂-induced model in hMNC. Thus, this nanocarrier formulation is promising to perform more preclinical investigations focusing on diseases involving oxidative mechanisms.

Syringic acid, a novel thyroid hormone receptor-β agonist, ameliorates propylthiouracil-induced thyroid toxicity in rats

The aim of this study was to evaluate the potential of syringic acid (SA) against propylthiouracil (PTU)-induced hypothyroidism in rats. SA at a prestandardized dose, 50 mg/kg/day, was orally administered to PTU-induced hypothyroid rats for 30 days, and alterations in the levels of serum triiodothyronine (T₃ ), thyroxine (T₄ ), thyrotropin (TSH), alanine transaminase (ALT), and aspartate transaminase (AST); tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6); total cholesterol (CHOL) and triglycerides (TG); hepatic lipid peroxidation (LPO) and antioxidants (superoxide dismutase, catalase, glutathione peroxidase, and glutathione content), as well as histological changes in liver and thyroid were examined. The molecular interactions of the ligand, SA, with thyroid-related protein targets, such as human thyroid hormone receptor β (hTRβ), and thyroid peroxidase (TPO) protein, were studied using molecular docking. Whereas in hypothyroid animals, T₄ , T₃ , and antioxidants were decreased, there was an increase in TSH, TNF-α, IL-6, ALT, AST, and hepatic LPO; administration of SA in PTU-induced animals reversed all these indices to near normal levels. SA also improved the histological features of liver and thyroid gland. Our study clearly demonstrates SA as a novel thyroid agonist for augmenting the thyroid functions in rats. Molecular docking analysis reveals that SA possesses good binding affinity toward both the targets, hTRβ and TPO. Through this approach, for the first time we provide the evidence for SA as a novel thyroid agonist and suggest a receptor-mediated mechanism for its thyroid stimulatory potential.

Pharmacological Potential and Chemical Characterization of Bridelia ferruginea Benth.-A Native Tropical African Medicinal Plant

To avail the possible pharmacological actions of Brideliaferruginea Benth., the present investigation was designed to quantitatively analyze the total flavonoid and phenolic contents and assess the various antioxidant and enzyme inhibition properties of leaf and stem bark extracts (ethyl acetate, water and methanolic) of B. ferruginea. Anti-proliferative effect was also investigated against human colon cancer cells (HCT116) as well as the antimicrobial potential against multiple bacterial and fungal (yeasts and dermatophytes) strains. The methanolic and water extracts of the stem bark demonstrated the highest phenolic content (193.58 ± 0.98 and 187.84 ± 1.88 mg/g, respectively), while the leaf extracts showed comparatively higher flavonoid contents (24.37-42.31 mg/g). Overall, the methanolic extracts were found to possess the most significant antioxidant potency. Compared to the other extracts, methanolic extracts of the B. ferruginea were revealed to be most potent inhibitors of acetyl- and butyryl-cholinesterases, tyrosinase α-amylase, except α-glucosidase. Only the ethyl acetate extracts were found to inhibit glucosidase. Additionally, the stem bark methanolic extract also showed potent inhibitory activity against E. coli and gram-positive bacteria (MIC (minimum inhibitory concentration): 2.48-62.99 µg/mL), as well as all the tested fungi (MIC: 4.96-62.99 µg/mL). In conclusion, B. ferruginea can be regarded as a promising source of bioactive compounds displaying multifunctional pharmacological activities and thus is a potential candidate for further investigations in the endeavor to develop botanical formulations for pharmaceutical and cosmeceutical industries.

Targeting RNS/caveolin-1/MMP signaling cascades to protect against cerebral ischemia-reperfusion injuries: potential application for drug discovery

Reactive nitrogen species (RNS) play important roles in mediating cerebral ischemia-reperfusion injury. RNS activate multiple signaling pathways and participate in different cellular events in cerebral ischemia-reperfusion injury. Recent studies have indicated that caveolin-1 and matrix metalloproteinase (MMP) are important signaling molecules in the pathological process of ischemic brain injury. During cerebral ischemia-reperfusion, the production of nitric oxide (NO) and peroxynitrite (ONOO⁻), two representative RNS, down-regulates the expression of caveolin-1 (Cav-1) and, in turn, further activates nitric oxide synthase (NOS) to promote RNS generation. The increased RNS further induce MMP activation and mediate disruption of the blood-brain barrier (BBB), aggravating the brain damage in cerebral ischemia-reperfusion injury. Therefore, the feedback interaction among RNS/Cav-1/MMPs provides an amplified mechanism for aggravating ischemic brain damage during cerebral ischemia-reperfusion injury. Targeting the RNS/Cav-1/MMP pathway could be a promising therapeutic strategy for protecting against cerebral ischemia-reperfusion injury. In this mini-review article, we highlight the important role of the RNS/Cav-1/MMP signaling cascades in ischemic stroke injury and review the current progress of studies seeking therapeutic compounds targeting the RNS/Cav-1/MMP signaling cascades to attenuate cerebral ischemia-reperfusion injury. Several representative natural compounds, including calycosin-7-O-β-D-glucoside, baicalin, Momordica charantia polysaccharide (MCP), chlorogenic acid, lutein and lycopene, have shown potential for targeting the RNS/Cav-1/MMP signaling pathway to protect the brain in ischemic stroke. Therefore, the RNS/Cav-1/MMP pathway is an important therapeutic target in ischemic stroke treatment.

Protective effects of scutellarin on type II diabetes mellitus-induced testicular damages related to reactive oxygen species/Bcl-2/Bax and reactive oxygen species/microcirculation/staving pathway in diabetic rat

The goal of our study is to evaluate the effect of Scutellarin on type II diabetes-induced testicular disorder and show the mechanism of Scutellarin's action. We used streptozotocin and high-fat diet to establish type II diabetic rat model. TUNEL and haematoxylin and eosin staining were used to evaluate the testicular apoptotic cells and morphologic changes. Immunohistochemical staining was used to measure the expression level of vascular endothelial growth factor and blood vessel density in testes. Oxidative stress in testes and epididymis was tested by fluorescence spectrophotometer and ELISA. The expression of Bcl-2/Bax and blood flow rate in testicular vessels were measured by western blot and Doppler. Our results for the first time showed that hyperglycemia induced apoptotic cells and morphologic impairments in testes of rats, while administration of Scutellarin can significantly inhibit these damages. This effect of Scutellarin is controlled by two apoptotic triggers: ROS/Bcl-2/Bax and ROS/microcirculation/starving pathway.

Comparative effect of Citrus sinensis and carbimazole on serum T4, T3 and TSH levels

BACKGROUND

There are previous independent reports on the anti-thyroid property of Citrus sinensis. This isoflavones and phenolic acid-rich natural agent is widely consumed as dietary supplement, thus the need to investigate its comparative effect with a standard anti-thyroid drug on T4, T3 and thyroid stimulating hormone (TSH) levels.

OBJECTIVE

To compare the effect of Citrus sinensis and carbimazole (CARB) on blood levels of thyroid hormones (T4 and T3) and TSH.

MATERIALS AND METHODS

Male wistar albino rats weighing 100-150 g were employed in this research. The rats were randomly assigned to four groups of seven rats per group. Group I served as control and were administered distilled water while groups II-IV were administered with 1500 mg/kg of Citrus sinensis (fresh orange juice; FOJ), 0.1 μg/g of levothyroxine (LVT) and 0.01 mg/g of CARB, respectively, per oral once daily for 28 days. The animals were sacrificed under chloroform anaesthesia and blood sample collected by cardiac puncture and processed by standard method to obtain serum. TSH, T4 and T3 were assayed with the serum using ARIA II automated radioimmunoassay instrument.

RESULTS

The results showed that TSH level was significantly (P < 0.05) decreased in LVT treated group compared with the FOJ group. T4 was significantly (P < 0.05) decreased in the FOJ and CARB groups compared with the control and LVT groups. LVT significantly increased T4 when compared with FOJ group. T3 was significantly (P < 0.05) decreased in the CARB group compared with the control.

CONCLUSION

These findings suggest that FOJ alters thyroid hormones metabolism to reduce their serum levels with a compensatory elevations of TSH level in a direction similar to CARB.

Trans-ferulic acid-based solid lipid nanoparticles and their antioxidant effect in rat brain microsomes

In this study, stearic acid- and stearyl ferulate-based solid lipid nanoparticles containing trans-ferulic acid (SLN-FA and SLN-SF-FA, respectively), were prepared and characterized for loading efficiency, size and shape. In addition, by using rat brain microsomes, we evaluated in vitro the antioxidant activity of these formulations against three well known initiators of lipid peroxidation, such as AAPH, NADPH/ADP-Fe(3+) and SIN-1 which in turn generate the peroxyl and perferryl radicals as well as peroxynitrite, respectively. Commercially available FA and its ethyl ester (FAEE) were used as comparators. Both SLN-FA and SLN-SF-FA dose-dependently reduced lipid peroxidation induced by the three oxidants. Interestingly, SLN-SF-FA displayed greater efficacy (EC50) and potency (maximal activity) against AAPH- and NADPH/ADP-Fe(3+)-induced lipid peroxidation. Our results support the idea that this new formulations could facilitate the uptake of FA by the cells because of their lipophilic structure, thus increasing FA bioavailability. Furthermore, stearyl ferulate-based nanoparticles could prevent the degradation of FA entrapped on their structure, making FA almost entirely available to explicate its antioxidant power once released.

Protein tyrosine nitration and thiol oxidation by peroxynitrite-strategies to prevent these oxidative modifications

The reaction product of nitric oxide and superoxide, peroxynitrite, is a potent biological oxidant. The most important oxidative protein modifications described for peroxynitrite are cysteine-thiol oxidation and tyrosine nitration. We have previously demonstrated that intrinsic heme-thiolate (P450)-dependent enzymatic catalysis increases the nitration of tyrosine 430 in prostacyclin synthase and results in loss of activity which contributes to endothelial dysfunction. We here report the sensitive peroxynitrite-dependent nitration of an over-expressed and partially purified human prostacyclin synthase (3.3 μM) with an EC₅₀ value of 5 μM. Microsomal thiols in these preparations effectively compete for peroxynitrite and block the nitration of other proteins up to 50 μM peroxynitrite. Purified, recombinant PGIS showed a half-maximal nitration by 10 μM 3-morpholino sydnonimine (Sin-1) which increased in the presence of bicarbonate, and was only marginally induced by freely diffusing NO₂-radicals generated by a peroxidase/nitrite/hydrogen peroxide system. Based on these observations, we would like to emphasize that prostacyclin synthase is among the most efficiently and sensitively nitrated proteins investigated by us so far. In the second part of the study, we identified two classes of peroxynitrite scavengers, blocking either peroxynitrite anion-mediated thiol oxidations or phenol/tyrosine nitrations by free radical mechanisms. Dithiopurines and dithiopyrimidines were highly effective in inhibiting both reaction types which could make this class of compounds interesting therapeutic tools. In the present work, we highlighted the impact of experimental conditions on the outcome of peroxynitrite-mediated nitrations. The limitations identified in this work need to be considered in the assessment of experimental data involving peroxynitrite.

Comparison on phenolic compounds and antioxidant properties of cabernet sauvignon and merlot wines from four wine grape-growing regions in China

The antioxidant activities in the Cabernet Sauvignon and Merlot wines from four wine grape-growing regions in China were measured by different analytical assays: 2,2-diphenyl-1-picrylhydrazyl (DPPH·), cupric reducing antioxidant capacity (CUPRAC), superoxide radical-scavenging activity (SRSA) and the contents of total phenols, total flavonoids, total flavanols and total anthocyanins were determined. The results showed that the contents of phenolic compounds and the levels of antioxidant activity in the wine samples greatly varied with cultivar and environmental factors of vine growth. The contents of phenolic compounds and antioxidant activities in Cabernet Sauvignon and Merlot wines from the Yuquanying region of Ningxia were significantly higher than other three regions, followed by the wines from Shacheng region of Hebei, and these parameters were the lowest in Cabernet Sauvignon and Merlot wines from the Changli regions of Hebei and Xiangning region of Shanxi. Taken together, a close relationship between phenolic subclasses and antioxidant activity was observed for the wine samples. Moreover, there were significant discrepancies in the individual phenolic composition and content of four regional Cabernet Sauvignon and Merlot wines, among which the individual phenolic compounds (catechin, epicatechin, cinnamic acid, quercetin-3-O-glucuronide, quercetin-3-O-glucoside, laricitrin-3-O-glucoside and isorhamnetin-3-O-glucoside) revealed a significant correlation (p < 0.05) with the antioxidant capacity in present study, especially for catechin and epicatechin.

Evaluation of antioxidant and free radical scavenging capacities of polyphenolics from pods of Caesalpinia pulcherrima

Thirteen polyphenolics were isolated from fresh pods of Caesalpinia pulcherrima using various methods of column chromatography. The structures of these polyphenolics were elucidated as gallic acid (1), methyl gallate (2), 6-O-galloyl-d-glucoside (3), methyl 6-O-galloyl-β-d-glucoside (4), methyl 3,6-di-O-galloyl-α-d-glucopyranoside (5), gentisic acid 5-O-α-d-(6'-O-galloyl)glucopyranoside (6), guaiacylglycerol 4-O-β-d-(6'-O-galloyl)glucopyranoside (7), 3-methoxy-4-hydroxyphenol 1-O-β-d-(6'-O-galloyl) glucopyranoside (8), (+)-gallocatechin (9), (+)-catechin (10), (+)-gallocatechin 3-O-gallate (11), myricetin 3-rhamnoside (12), and ampelopsin (13). All isolated compounds were tested for their antioxidant activities in the 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl, and peroxynitrite radicals scavenging assays. Among those compounds, 11, 12, and 2 exhibited the best DPPH-, hydroxyl-, and peroxynitrite radical-scavenging activities, respectively. Compound 7 is a new compound, and possesses better scavenging activities towards DPPH but has equivalent hydroxyl radical scavenging activity when compared to BHT. The paper is the first report on free radical scavenging properties of components of the fresh pods of Caesalpinia pulcherrima. The results obtained from the current study indicate that the free radical scavenging property of fresh pods of Caesalpinia pulcherrima may be one of the mechanisms by which this herbal medicine is effective in several free radical mediated diseases.

Spectrophotometric studies of the reaction of quercetin with peroxynitrite at different pH

Peroxynitrite (ONOOH/ONOO-) which is formed in vivo under oxidative stress is a strong oxidizing and nitrating agent. It has been reported that several flavonoids, including quercetin, inhibit the peroxynitrite-induced oxidation and/or nitration of several molecules tested; however, the mechanism of their protective action against peroxynitrite is not univocally resolved. The kinetics of the reaction of quercetin with peroxynitrite was studied by stopped-flow as well as by conventional spectrophotometry under acidic, neutral and alkaline pH. The obtained results show that the protective mechanism of quercetin against peroxynitrite toxicity cannot be explained by direct scavenging of peroxynitrite. We propose that quercetin acts via scavenging intermediate radical products of peroxynitrite decomposition (it is an excellent scavenger of ·NO2) and/or via reduction of target radicals formed in the reaction with peroxynitrite.

UVA-induced melanogenesis and modulation of glutathione redox system in different melanoma cell lines: the protective effect of gallic acid

Oxidative stress has been suggested to play a role in ultraviolet A (UVA)-mediated melanogenesis. Glutathione (GSH) and GSH-related enzymes including γ-glutamate cysteine ligase (γ-GCL) and glutathione S-transferase (GST) are important antioxidant defenses responsible for maintaining cellular redox balance. Hence, improving GSH redox system to cope with oxidative insults may be essential for attenuation of abnormal melanin production. Gallic acid (GA), a dietary phenolic, has been shown to provide beneficial effects against hyperpigmentation possibly through its antioxidant properties. This study thus aimed to assess the antimelanogenic action of GA with regard to modulation of GSH-GCL system and GST in two melanoma cell lines, lightly pigmented G361 human melanoma and more pigmented B16F10 mouse melanoma cells, irradiated with UVA. G361 cells were shown to have lower basal GSH content and GST activity than B16F10 cells. Moreover, GA provided antimelanogenic effects in correlation with promotion of GSH levels, GST activity as well as γ-GCL and GST mRNA in both G361 and B16F10 cells at 2-h post-irradiation. In summary, GA exhibits protective effects on UVA-mediated melanogenesis possibly through improvement of GSH-related antioxidant defenses. Furthermore, different redox state in G361 and B16F10 cells may affect the responses of melanoma cells to GA.

Inhibitory Effects of Conjugated Epicatechin Metabolites on Peroxynitrite-mediated Nitrotyrosine Formation

Previously, we identified four metabolites of (−)-epicatechin in blood and urine: (−)-epicatechin-3'-O-glucuronide (E3'G), 4'-O-methyl-(−)-epicatechin-3'-O-glucuronide (4'ME3'G), (−)-epicatechin-7-O-glucuronide (E7G), and 3'-O-methyl-(−)-epicatechin-7-O-glucuronide (3'ME7G) (Natsume et al. Free Radical Biol. Med. 34, 840-849, 2003). The aim of the current study was to compare the antioxidative activities of these metabolites with that of their parent compound. After oral administration of (−)-epicatechin, E3'G and 4'ME3'G were isolated from human urine, and E7G and 3'ME7G isolated from rat urine. We found that these compounds inhibited peroxynitrite-mediated tyrosine nitration, in the following order of potency: E3'G > (−)-epicatechin > E7G = 3'ME7G. = 4'ME3'G. These results demonstrate that the metabolites of (−)-epicatechin retain antioxidative activity on peroxynitrite-induced oxidative damages to some extent.

Peroxynitrite and nitrosoperoxycarbonate, a tightly connected oxidizing-nitrating couple in the reactive nitrogen-oxygen species family: new perspectives for protection from radical-promoted injury by flavonoids

Peroxynitrite is the product of the reaction of nitric oxide with superoxide radical and is implicated in the pathogenesis of a wide variety of human diseases, being responsible for in-vivo oxidation/nitration events. Nitrosoperoxycarbonate anion, formed by the interaction of peroxynitrite with CO2/bicarbonate at physiological concentrations, provides a new interpretation of oxidative/nitrative processes formerly attributed to peroxynitrite. The aim of this review is to summarize the chemistry and biology of peroxynitrite and radical species related to nitrosoperoxycarbonate anion, as well as the information available regarding the molecular mechanisms that determine and regulate radical-promoted injury by the two tightly connected species at physiological concentrations. Interception of carbonate and nitro radicals produced by interaction of peroxynitrite with CO2/bicarbonate, as in-vivo prevention of pathological events, creates new perspectives for the evaluation of safe scavengers of oxidative/nitrative stress at the physiological level. In this respect, natural products such as flavonoids hold a preeminent position among the vast array of compounds endowed with such properties.

In vitro effects of peroxynitrite treatment on fish liver catalase activity

The effect of peroxynitrite (PN), a highly toxic agent, on catalase (CAT) activity in fish liver microsomal homogenates was determined. PN was synthesized by mixing acidic hydrogen peroxide solution with sodium nitrite solution and then adding sodium hydroxide solution into the mixture in order to stabilize the highly labile compound peroxynitrous acid (ONOOH) in peroxynitrite anion form (ONOO(- )). The effect of PN and decomposed peroxynitrite (DPN), prepared by preincubation with HCl, was monitored by using a constant amount of homogenate containing the CAT enzyme. Significant losses were observed in the CAT activity of fish liver enzyme after treatment with PN and also with DPN products, the inhibitory effect of PN being slightly more pronounced than that of DPN. IC(50) values were 5.5 and 8.5 microM for PN and DPN, respectively. The PN inhibition of CAT activity is due to both the effects of the secondary and decomposition products of PN and its nitration and oxidation effects on the amino acid residues of the enzyme.

Evaluation of the accuracy of antioxidant competition assays: incorrect assumptions with major impact

The activity of antioxidants is frequently determined in competition assays. In these assays an antioxidant (A) and a detector molecule (D) compete for the reactive species (R). The competitive inhibitory effect of A on the reaction of D with R is a measure of the antioxidant activity of A. In determining the activity of A, it is in general incorrectly assumed that the concentrations of A and D remain equal to the initial concentration. However, the principle of the assay is that some A and D is consumed and consequently the concentrations of A and D will decrease during a competition assay, resulting in a deviation in the observed antioxidant activity. Computer modeling was used to obtain a graphical tool to estimate the extent of the deviation caused by the incorrect assumption that the concentrations of A and D do not decrease. Several competition assays were evaluated using this graphical tool, demonstrating that frequently inaccurate antioxidant activities have been reported. In general, differences between antioxidants are underestimated and the activity of all antioxidants shifts toward the antioxidant activity of D. A strategy is provided to improve the accuracy of a competition assay. To obtain accurate results in a competition assay, the reaction rate constant of the detector molecule with the reactive species should be comparable to that of the antioxidant. In addition, the concentration of the reactive species should be as low as possible.

Nitrite-glucose-glucose oxidase system directly induces rat heart homogenate oxidation and tyrosine nitration: effects of some flavonoids

Protein tyrosine nitration is a common post-translational modification occurring under conditions of nitrative/oxidative stress in a number of diseases. It has been found that in the presence of nitrite and hydrogen peroxide, hemoprotein catalyzes protein tyrosine nitration. In this paper, it was found that in heart homogenate, protein nitration and oxidation could be induced by a nitrite-glucose-glucose oxidase system without addition of exogenous heme or hemoprotein. Several structural diversity flavonoids (quercetin, rutin, baicalein, baicalin, apigenin, puerarin, and (+)-catechin) could, more or less, protect rat heart homogenate from oxidative and nitrative injury induced by nitrite-glucose-glucose oxidase in vitro. The inhibitory effects of flavonoids on protein nitration and lipid peroxidation were consistent with their antioxidant activities, whereas the inhibitory effects on protein oxidation were almost contrary to their antioxidant activities. These results mean that nitrite-glucose-glucose oxidase system can cause heart homogenate protein nitration and protein oxidation in different pathways, and those flavonoids with strong antioxidant activities may contribute their protective effect partly through inhibiting protein nitration.

Scutellaria baicalensis enhances the anti-diabetic activity of metformin in streptozotocin-induced diabetic Wistar rats

Oxidative stress is the root cause of diabetic macro- and microvascular complications. Biochemical and epidemiological studies indicate that current treatments for diabetes do not reduce risks of developing complications, suggesting their inability to alleviate the levels of oxidative stress. This study in streptozotocin (STZ)-induced diabetic rats was carried out to investigate the effect of combining the antidiabetic drug, metformin, with an ethanolic extract of Scutellaria baicalensis, a plant whose root is known for its radical scavenging activity. Three groups of STZ-induced diabetic rats were given the following treatments for 30 days: (1) metformin 500 mg/kg, (2) S. baicalensis 400 mg/kg, (3) metformin 500 mg/kg + S. baicalensis extract 400 mg/kg. In addition, vehicle-treated diabetic and nondiabetic controls were used in the experiment. The rats treated with S. baicalensis and metformin + S. baicalensis had elevated hepatic activities of the antioxidant enzymes--superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) compared to the vehicle- and metformin-treated diabetic groups (p < 0.05). Plasma and hepatic lipid peroxide concentrations in the herb-treated and herb + metformin-treated groups were also significantly reduced (p < 0.05). In addition, the combined treatment caused significant elevations of plasma and pancreatic insulin levels and reductions of plasma and hepatic triglycerides (TG) and cholesterol levels. The study thus showed that S. baicalensis enhanced the antidiabetic effect of metformin in STZ-induced diabetic rats by improving the antioxidant status. It also increased pancreatic insulin content as well as improved the lipid profile in these rats.

Optimization of solid-liquid extraction of resveratrol and other phenolic compounds from milled grape canes (Vitis vinifera)

Optimization of the solid-liquid extraction conditions for trans-resveratrol, trans--viniferin, ferulic acid, and total phenolics from milled grape canes has been investigated. The temperature and ethanol concentration were found to be major process variables for all responses, whereas the solvent to solid ratio was found not to be significant for any of the responses studied. The yields of trans-resveratrol, trans--viniferin, and total phenolics increased with increasing temperature. Maximum yields of trans-resveratrol (4.25 mg/g dw), trans--viniferin (2.03 mg/g), and total phenolics (9.28 mg/g dw) were predicted from the combination of a moderate ethanol concentration (50-70%) and the highest temperature (83.6 degrees C), whereas an ethanol concentration of 35% at the lowest temperature studied (16.4 degrees C) was optimal for the extraction of ferulic acid (1.05 mg/g dw). Effective diffusivity values of resveratrol in the solid phase, D eff for different extraction conditions, were calculated by fitting the experimental results to a model derived from the Fick's second law. Effective diffusivity of resveratrol in the solid phase varied from 3.1 x 10 (-13) to 26.6 x 10 (-13) m (2) s (-1) with changing extraction conditions. The increase in effective diffusivity of resveratrol was observed with increasing temperature, and the highest predicted level was obtained when using 54% ethanol/water mixture at 83.6 degrees C. The increase in ethanol concentration exhibited the favorable effect up to 50-55%, thereafter effective diffusivity decreased with a further increase in concentration.

A Multipumping Flow System for In Vitro Screening of Peroxynitrite Scavengers

Peroxynitrite anion is a reactive nitrogen species formed in vivo by the rapid, controlled diffusion reaction between nitric oxide and superoxide radicals. By reacting with several biological molecules, peroxynitrite may cause important cellular and tissue deleterious effects, which have been associated with many diseases. In this work, an automated flow-based procedure for the in vitro generation of peroxynitrite and subsequent screening of the scavenging activity of selected compounds is developed. This procedure involves a multipumping flow system (MPFS) and exploits the ability of compounds such as lipoic acid, dihydrolipoic acid, cysteine, reduced glutathione, oxidized glutathione, sulindac, and sulindac sulfone to inhibit the chemiluminescent reaction of luminol with peroxynitrite under physiological simulated conditions. Peroxynitrite was generated in the MPFS by the online reaction of acidified hydrogen peroxide with nitrite, followed by a subsequent stabilization by merging with a sodium hydroxide solution to rapidly quench the developing reaction. The pulsed flow and the timed synchronized insertion of sample and reagent solutions provided by the MPFS ensure the establishment of the reaction zone only inside the flow cell, thus allowing maximum chemiluminescence emission detection. The results obtained for the assayed compounds show that, with the exception of oxidized glutathione, all are highly potent scavengers of peroxynitrite at the studied concentrations. ( Journal of Biomolecular Screening 2007:875-880)

Dipyrone and aminopyrine are effective scavengers of reactive nitrogen species

Reactive nitrogen species (RNS), namely nitric oxide (NO*) and peroxynitrite (ONOO-) are produced in the inflammatory sites and may contribute to the deleterious effects of inflammation. The aim of the present study was to evaluate the putative scavenging effect of a particular group of non-steroidal anti-inflammatory drugs (NSAIDs), the pyrazolone derivatives dipyrone, aminopyrine, isopropylantipyrine, and antipyrine against RNS, using in vitro non-cellular screening systems. The results obtained showed that dipyrone and aminopyrine were highly potent scavengers of NO* and ONOO- while antipyrine exerted little effect and isopropylantipyrine no effect whatsoever against these two RNS and that, in the presence of bicarbonate, the scavenging potencies of both dipyrone and aminopyrine were slightly decreased. It could thus be inferred that the observed scavenging effects may be of therapeutic benefit for patients under anti-inflammatory treatment with dipyrone and aminopyrine in the case of overproduction of RNS. On the other hand, the possible depletion of physiological NO* concentrations, namely at the gastrointestinal tract as well as the formation of reactive derivatives of aminopyrine and/or dipyrone, resulting from their reaction with RNS, may otherwise be harmful for these patients.

Antioxidant activity of β-blockers: An effect mediated by scavenging reactive oxygen and nitrogen species?

The therapeutic effects of beta-blockers are normally explained by their capacity to block the beta-adrenoceptors, however, some of the beneficial cardiovascular effects shown by this group of compounds have already been associated with the antioxidant properties that some of them seem to possess. The beta-blockers atenolol, labetalol, metoprolol, pindolol, propranolol, sotalol, timolol, and carvedilol were tested for their putative scavenging activity for ROS (O(2)(-), H(2)O(2), HO(.), HOCl, and ROO(.)) and RNS ((.)NO and ONOO(-)). Some of the studied compounds are effective ROS and/or RNS scavengers, these effects being possibly useful in preventing oxidative damage verified in hypertension as well as in other cardiovascular diseases that frequently emerge in association with oxidative stress.

Drugs modulating the biological effects of peroxynitrite and related nitrogen species

The term "reactive nitrogen species" includes nitrogen monoxide, commonly called nitric oxide, and some other remarkable chemical entities (peroxynitrite, nitrosoperoxycarbonate, etc.) formed mostly from nitrogen monoxide itself in biological environments. Regardless of the specific mechanisms implicated in their effects, however, it is clear that an integrated pharmacological approach to peroxynitrite and related species is only just beginning to take shape. The array of affected chemical and pathological processes is extremely broad. One of the most conspicuous mechanisms observed thus far has been the scavenging of the peroxynitrite anion by molecules endowed with antioxidant activity. This discovery has in turn lent great significance to several naturally occurring and synthetic antioxidants, which usually protect not only against oxidative reactions, but also from nitrating ones, both in vitro and in vivo. This has proven to be beneficial in different tissues, especially within the central nervous system. Taking these results and those of other biochemical investigations into account, many research lines are currently in progress to establish the true potential of reactive nitrogen species deactivators in the therapy of neurological diseases, ischemia-reperfusion damage, renal failure, and lung injury, among others.

Use of Fluorescence Probes for Detection of Reactive Nitrogen Species: A Review

The biological and toxicological effects that have been attributed to reactive nitrogen species (RNS) are increasingly stirring the scientific inquisitiveness about the molecular mechanisms involved. However, RNS present some characteristics that complicate their detection, namely their short lifetime and the normal presence of a variety of endogenous compounds capable of reacting with these reactive species, when the studies are performed in biological matrices. The development of methodologies capable of circumvent these difficulties is thus of fundamental importance. Fluorescence probes are particularly important due to their high sensibility and usefulness in temporal and spatial monitoring of RNS, particularly in microanalysis conditions in biological media akin to cells or tissues. In the present review is given an account of the fluorescence probes that have been used for detection of nitric oxide (*NO), peroxynitrite anion (ONOO-), as well as of some of its derivatives in biological and nonbiological media.

Protection by flavonoids against the peroxynitrite-mediated oxidation of dihydrorhodamine

Peroxynitrite anion is a reactive and short-lived species and its formation in vivo has been implicated in several human diseases. In view of the potential usefulness of compounds that can protect against peroxynitrite or their reactive intermediates, a study focused on flavonoid compounds was carried out. Since the reactivity of peroxynitrite may be modified by Co2/HCO3-, which is an important plasma buffer, the protection of flavonoids against peroxynitrite was evaluated by their ability to inhibit the peroxynitrite-mediated dihydrorhodamine (DHR123) oxidation with or without physiological concentrations of bicarbonate. Flavonoids from different classes were studied to elucidate which structural features are required for an effective protection. The most efficient flavonoids on protecting DHR123 against oxidation by peroxynitrite have their ability diminished in the presence of bicarbonate, but they maintain the hierarchy established in the absence of bicarbonate. The flavones are the most effective flavonoids and their effects depend mainly on the number of hydroxyl groups. These must include either a catechol group in the B-ring or a hydroxyl group at the 3-position. This work also included some isoflavones, flavanones and a flavanol, which enable us to conclude about the importance of another structural feature: the 2,3-double bond. These results indicate that the ability of flavonoids to protect against peroxynitrite depends on some structural features, also important to scavenge oxygen free radicals and to chelate metal ions. The most efficient flavonoids are effective at low concentrations with IC50 of the same magnitude as Ebselen, a selenocompound that has been reported to be excellent at protecting against peroxynitrite. Their effectiveness at low concentrations is an important aspect to take into account when characterizing a compound as an antioxidant with biological interest.

Pindolol is a potent scavenger of reactive nitrogen species

Pindolol is an indolic drug that has been shown to enhance and/or accelerate selective serotonin specific reuptake inhibitors (SSRI)-induced antidepressant (AD) effect, even though the respective mechanism is still unclear. It has been demonstrated that inhibition of nitric oxide (*NO) synthesis in CNS produces anxiolytic and AD-like behavioural effects in a variety of animal paradigms. On the other hand, sustained high levels of *NO may be deleterious to CNS, predominantly due to the formation of peroxynitrite anion (ONOO-), which is generated via reaction of *NO with superoxide radical (O2*-). Therefore, the purpose of the present study was to characterize the putative pindolol scavenging effect on *NO, ONOO-, and O2*-, using in vitro non-cellular systems. The obtained results clearly show that pindolol is a potent scavenger of *NO (IC50 of 449+/-33 microM) and ONOO- (IC50 of 131+/-24 microM). Additionally, the scavenging effect of pindolol increased almost 8 times in the presence of 25 mM NaHCO3 (IC50 of 17+/-3 microM), which indicates that pindolol efficiently scavenges reactive species that are produced from the ONOO-/CO2 reaction such as the nitrogen dioxide radical (*NO2) and the carbonate radical anion (CO3*-). These effects may contribute for the reduction of SSRI antidepressant latency that has been attributed to pindolol and may also constitute an additional value for this drug when depression is associated with pro-oxidant neurodegenerative diseases.

Health promotion by flavonoids, tocopherols, tocotrienols, and other phenols: direct or indirect effects? Antioxidant or not?

Foods and beverages rich in phenolic compounds, especially flavonoids, have often been associated with decreased risk of developing several diseases. However, it remains unclear whether this protective effect is attributable to the phenols or to other agents in the diet. Alleged health-promoting effects of flavonoids are usually attributed to their powerful antioxidant activities, but evidence for in vivo antioxidant effects of flavonoids is confusing and equivocal. This may be because maximal plasma concentrations, even after extensive flavonoid intake, may be low (insufficient to exert significant systemic antioxidant effects) and because flavonoid metabolites tend to have decreased antioxidant activity. Reports of substantial increases in plasma total antioxidant activity after flavonoid intake must be interpreted with caution; findings may be attributable to changes in urate concentrations. However, phenols might exert direct effects within the gastrointestinal tract, because of the high concentrations present. These effects could include binding of prooxidant iron, scavenging of reactive nitrogen, chlorine, and oxygen species, and perhaps inhibition of cyclooxygenases and lipoxygenases. Our measurements of flavonoids and other phenols in human fecal water are consistent with this concept. We argue that tocopherols and tocotrienols may also exert direct beneficial effects in the gastrointestinal tract and that their return to the gastrointestinal tract by the liver through the bile may be physiologically advantageous.

In vitro scavenging activity for reactive oxygen and nitrogen species by nonsteroidal anti-inflammatory indole, pyrrole, and oxazole derivative drugs

This study was undertaken to evaluate the scavenging activity for reactive oxygen species (ROS) and reactive nitrogen species (RNS) by several nonsteroidal anti-inflammatory drugs (NSAIDs), namely indole derivatives (indomethacin, acemetacin, etodolac), pyrrole derivatives (tolmetin and ketorolac), and an oxazole derivative (oxaprozin). The inhibition of prostaglandin synthesis constitutes the primary mechanism of the anti-inflammatory action of these drugs. Nevertheless, it has been suggested that the anti-inflammatory activity of NSAIDs may be also partly due to their ability to scavenge ROS and RNS and to inhibit the respiratory burst of neutrophils triggered by various activator agents. Thus, the scavenging activity of these NSAIDs was evaluated against an array of ROS (O(2)(-), HO, HOCl, and ROO) and RNS (NO and ONOO(-)) using noncellular in vitro systems. The results obtained demonstrated that tolmetin, ketorolac, and oxaprozin were not active against O(2)(-), while acemetacin, indomethacin, and etodolac exhibited concentration-dependent effects. Oxaprozin was also the least active scavenger for HO, among all the tested NSAIDs shown to be active. The scavenging effect for HOCl was not observed for any of the tested NSAIDs. The ROO was effectively scavenged by etodolac, with the other tested NSAIDs being much less active. NO and ONOO(-) were scavenged by all the tested NSAIDs. These effects may strongly contribute to the anti-inflammatory therapy benefits that may be attained with some of the studied NSAIDs.

Characterization of antioxidant and antiglycation properties and isolation of active ingredients from traditional chinese medicines

There is considerable interest in the isolation of more potent antioxidant compounds to treat diseases involving oxidative stress. Thirty-three traditional Chinese medicine (TCM) extracts were examined for their antioxidant activity using the 2,2'-azinobis[3-ethylbenzothiazoline-6-sulfonate] (ABTS) assay. Five extracts with high activity (Cratoxylum cochinchinense, Cortex magnoliae officinalis, Psoralea corylifolia L, Curculigo orchioides Gaertn, and Glycyrrhiza uralensis Fisch.) were selected for further characterization. C. cochinchinense outperformed other extracts in most of the assays tested except phospholipid peroxidation inhibition, where P. corylifolia L showed higher activity. C. cochinchinense was particularly potent in inhibiting the formation of advanced glycation end products on proteins and strongly inhibited hypochlorous acid-induced DNA damage. We attempted to isolate the active ingredients from C. cochinchinense and obtained an extract (YCT) containing at least 90% mangiferin as identified by HPLC and mass spectrometry. However, YCT showed significantly higher activity in assays of phospholipid peroxidation, inhibition of protein glycation, and superoxide (O(2)(?-)) and peroxynitrite (ONOO(-)) scavenging, as compared with mangiferin, suggesting that the nonmangiferin constituents of YCT contribute to its additional antioxidant activities.

Phenolic antioxidants and the protection of low density lipoprotein from peroxynitrite-mediated oxidations at physiologic CO2

Dietary phenolic antioxidants have been shown to prevent LDL modifications mediated by several physiologic oxidants including peroxynitrite. However, more recent data demonstrated that CO(2) affected the fate of peroxynitrite in biological fluids and significantly reduced peroxynitrite scavenging by polyphenols, raising doubts concerning their antioxidant activity. We found that the oxidation of LDL lipids mediated by peroxynitrite decreased in the presence of bicarbonate, while Trp oxidation and 3-nitroTyr formation increased, suggesting a redirection of peroxynitrite reactivity toward the protein moiety. We therefore evaluated the protective activity of some phenolic antioxidants (quercetin, oleuropein, resveratrol, (+)-catechin, (-)-epicatechin, tyrosol, alpha- and gamma-tocopherol, ascorbate) on peroxynitrite-mediated oxidation of LDL aromatic residues. Some of these phenols protected LDL Trp from oxidation better than ascorbate or alpha-tocopherol, although protection at 100 microM did not exceed 30-40%. However, the same phenolic antioxidants were more active in inhibiting 3-nitroTyr formation and those with a catechin structure provided significant protection (IC(50%) 40-50 microM). Red wine, a polyphenol-rich beverage, showed a protective effect comparable to that of the most active phenolic antioxidants. Direct EPR studies showed that bicarbonate significantly increased the peroxynitrite-dependent formation of O-semiquinone radicals in red wine, supporting the hypothesis that polyphenols are efficient scavengers of radicals formed by peroxynitrite/CO(2). Ascorbate was a poor inhibitor of peroxynitrite/CO(2)-induced LDL tyrosine nitration, but the simultaneous addition to the most active polyphenols halved their IC(50%). In conclusion, although cooperation with other antioxidants can further decrease the IC(50%) of polyphenolics, as demonstrated for ascorbate, their antioxidant activity appears to occur at concentrations at least 1 order of magnitude higher than their bioavailability.

Interference of the polyphenol epicatechin with the biological chemistry of nitric oxide- and peroxynitrite-mediated reactions

The formation of reactive nitrogen species in mammalians has both beneficial and undesirable effects. Nitric oxide (NO) production in endothelial cells leads to vascular smooth muscle relaxation, but if reactive nitrogen species are generated in high amounts by cells under inflammatory conditions they are toxic. Flavonoids like (-)-epicatechin show an inverse association of their intake with diseases thought to be associated with overproduction of reactive nitrogen species. We found that the formation of cyclic GMP in cultured porcine aortic endothelial cells was not affected by up to 1 mM (-)-epicatechin. Half maximal inhibition of interferon-gamma/lipopolysaccharide induced nitrite accumulation in murine macrophages required about 0.5 mM of the flavonoid. In contrast, nitration of free tyrosine triggered by 0.1 and 1 mM authentic peroxynitrite was inhibited by (-)-epicatechin with IC(50) values of 6.6 and 28.0 microM, respectively. The presence of 15 mM sodium bicarbonate had no significant effect. Nitration of protein-bound tyrosine in phorbol 12-myristate 13-acetate treated HL-60 cells in the presence of nitrite was inhibited by (-)-epicatechin at a similar concentration range (IC(50)=10-100 microM). Myeloperoxidase activity of phorbol 12-myristate 13-acetate stimulated HL-60 cells was inhibited by (-)-epicatechin with an IC(50) value of 77.4 microM. Epicatechin inhibited dihydrorhodamine oxidation by 50 microM authentic peroxynitrite and 1 mM 3-morpholino-sydnonimine with IC(50) values of 11.8 and 0.63 microM, respectively. Our data suggest that at up to 0.1 mM (-)-epicatechin preferentially inhibits NO-related nitration and oxidation reactions without affecting NO synthesis and cyclic GMP signaling.

Phenolic antioxidants: electrochemical behavior and the mechanistic elements underlying their anodic oxidation reaction

Electrochemical analysis has been widely used to assess activities of reductant antioxidants, but the mechanistic factors that determine reducing ability and their corresponding correlations remain to be explored further. In the present paper, the reactivity of a selection of phenolic compounds in anodic oxidation was investigated by cyclic voltammetry (CV). The effects of electron-donation ability, deprotonation equilibrium, stability of radicals and chemical hardness on reducing capacity were studied by computational chemistry methods and multiple linear regression analysis. The results suggested that all these factors made significant contributions to reducing potency although electron-donation ability of the parent molecule plays the most important role in the electrode reaction. With the majority of the compounds examined, the occurrence of multiple electrochemical reactions leading to irreversible anodic oxidation was implied by: (i) the characteristics of the radical cation intermediate; (ii) the propensity of the deprotonation reaction; and (iii) the reactivity of the parent molecule. Upon correlation analysis of oxidation potential and computed physicochemical descriptors, some new light was shed on the mechanism by which phenolic compounds act as antioxidant reductants in free radical reactions. A satisfactory multi-descriptor theoretical QSAR model was derived, which might be of predictive significance in the screening or design of new antioxidants.

Antiradical activity of different copper(II) Schiff base complexes and their effect on alloxan-induced diabetes

Considering the important role of antioxidants in biological systems, the group of copper(II) complexes derived from salicylaldehyde and alpha- or beta-alanine and its thiourea derivative and copper(II) complexes derived from pyruvic acid and beta-alanine were studied. The antiradical activity of the tested compounds was studied by both in vitro and in vivo methods. The chemical methods based on inhibition of INT-formazane or 3-nitrotyrosine formation were used for the evaluation of SOD-mimic and antiperoxynitrite activity, respectively. In the case of in vivo activity evaluation, an alloxan-induced diabetes mellitus model in mice was used, the mechanism of action of alloxan being closely connected with the formation of free radicals selectively damaging the pancreatic beta-cells. Since all the substances studied showed different positive effects, it is obvious that they have not acted only as a source of copper(II) ions but their effect is related to their specific chelate structure. The obtained results are a contribution to the knowledge of copper(II) Schiff base complexes with ligands of aldimine or ketimine type and form the basis for further preclinical tests of these bioactive agents in biological models of oxidative stress.

Goitrogenic activity ofp-coumaric acid in rats

The effects of three natural phenolic acids (caffeic, ferulic, and p-coumaric) on the rat thyroid gland were examined in a 3-week oral-treatment study. Forty male Wistar albino rats, divided into groups of 10 rats each and fed iodine-rich diet, were administered by gastrointestinal tube saline (control), caffeic acid, ferulic acid, or p-coumaric acid at a dose level of 0.25 micromol/kg/day for 3 weeks. The mean absolute and relative thyroid weights in caffeic, ferulic, or p-coumaric acid groups were significantly increased to 127 and 132%, 146 and 153%, or 189 and 201% compared to control value, respectively. Histological examination of the thyroids of p-coumaric acid group revealed marked hypertrophy and/or hyperplasia of the follicles. Caffeic or ferulic groups showed slight to moderate thyroid gland enlargement. Thyroid lesions in p-coumaric acid group were associated with significant increases in cellular proliferation as indicated by [(3)H]thymidine incorporation. In addition, the goitrogenic effect of p-coumaric acid was further confirmed by significant decreases (50%) in serum tri-iodothyronine (T(3)) and thyroxine (T(4)), and a parallel increase (90%) in serum thyroid stimulating hormone (TSH) compared to control group. These results indicate that administration of p-coumaric acid at relatively high doses induces goiter in rats.