Prooxidant activity of caffeic acid, dietary non-flavonoid phenolic acid, on Cu2+-induced low density lipoprotein oxidation

The power of the QUENCHER method in measuring total antioxidant capacity of foods: Importance of interactions between different forms of antioxidants

Antioxidants play a crucial role in maintaining human health by counteracting oxidative stress and regulating redox balance within the body. The mixture of various antioxidant compounds in different forms (i.e., free, bound, insoluble) in food creates a redox active environment both in the human body and in the food system. Acting as both electron donors and acceptors while interacting with each other can either result in antagonism through pro-oxidative effects, or synergism through regeneration of one antioxidant by another. During the antioxidant capacity measurement, besides the individual antioxidant effects of the antioxidant components, these effects that occur because of their interaction with each other should be also considered. Classical antioxidant capacity measurement methods mostly concentrate on the fractions of foods that can be extracted with either water, alcohol, lipid, or acid/alkaline solutions. Antioxidants that cannot be extracted with any solvent are mostly ignored in these methods. On the other hand, the QUENCHER method, which allows direct measurement of antioxidant capacity foods without extraction, offers a rational solution to the limitations of traditional extraction-based methods. This approach considers the antioxidant capacity and interactions of all antioxidant forms that can be found in a food matrix, at the same time. This review provides detailed insights into the advantages of QUENCHER as a holistic approach for the accurate measurement of the antioxidant capacity of foods.

The Apoptotic Effect of Caffeic or Chlorogenic Acid on the C32 Cells That Have Simultaneously Been Exposed to a Static Magnetic Field

The induction of apoptosis is one of the main goals of the designed anti-cancer therapies. In recent years, increased attention has been paid to the physical factors such as magnetic fields and to the natural bioactive compounds and the possibilities using them in medicine. Hence, the aim of this study was to evaluate the anti-tumor effect of caffeic or chlorogenic acid in combination with a moderate-strength static magnetic field on C32 melanoma cells by assessing the effect of both factors on the apoptotic process. The apoptosis of the C32 cells was evaluated using a flow cytometry analysis. The expression of the apoptosis-associated genes was determined using the RT-qPCR technique. The caspase activity and the concentration of the oxidative damage markers were also measured. It was found that phenolic acids and a static magnetic field trigger the apoptosis of the C32 cells and also affect the expression of the genes encoding the apoptosis regulatory proteins. In conclusion, our study indicated that both of the phenolic acids and a static magnetic field can be used supportively in the treatment of melanoma and that caffeic acid is more pro-apoptotic than chlorogenic acid.

The Phytoremediation Potential and Physiological Adaptive Response of Tamarix tetrandra Pall. Ex M. Bieb. during the Restoration of Chronosequence Fly Ash Deposits

The challenging process of identifying and selecting plant species suited to the phytoremediation of fly ash (FA) dumps involves studying their functional properties and physiological response to a deficit of essential elements and toxicity from heavy metal(loid)-induced oxidative stress. We hypothesised that Tamarix tetrandra has high potential to be used for the phytoremediation of FA deposit sites thanks to its secretion strategy and antioxidative system. In this study, this hypothesis was examined by determining the bioconcentration and translocation factors for As, B, Cr, Cu, Mn, Ni, Se and Zn at the FA disposal lagoons at the ‘Nikola Tesla A’ thermal power plant in Obrenovac, Serbia, three (lagoon L1) and eleven (lagoon L2) years after the phytoremediation process had begun, and by measuring parameters of photosynthetic efficiency and chlorophyll concentration, non-enzymatic antioxidant defence (carotenoids, anthocyanins and phenolics), oxidative stress (concentration of malondialdehyde—MDA) and total antioxidant capacity to neutralise DPPH free radical activity. Tamarisk not only showed the ability to phytostabilise As, Cr and Ni and to accumulate low-availability Mn, Zn and Cu, but also the potential to maintain the structural and functional integrity of cell membranes and stable vitality at L1 under multiple stress conditions due to the high synthesis of phenols and tolerance to increased salinity. However, toxic concentrations of B and Se in leaves induced oxidative stress in tamarisk at L2 (reflected in higher MDA content and lower vitality) and also decreased the synthesis of chlorophyll, carotenoids, anthocyanins and total antioxidant activity. In addition, the prooxidative behaviour of phenols in the presence of spin-stabilising metals from FA could also have resulted in their weaker antioxidant protection at L2. These findings indicate that the choice of tamarisk was justified, but only at the beginning of the phytoremediation process because its presence contributed to an improvement in the harsh conditions at FA deposit sites and the creation of more favourable conditions for new plant species. This knowledge can be of great importance when planning sustainable ash deposit site management worldwide.

Role of Iron Chelation and Protease Inhibition of Natural Products on COVID-19 Infection

Although the epidemic caused by SARS-CoV-2 callings for international attention to develop new effective therapeutics, no specific protocol is yet available, leaving patients to rely on general and supportive therapies. A range of respiratory diseases, including pulmonary fibrosis, have been associated with higher iron levels that may promote the course of viral infection. Recent studies have demonstrated that some natural components could act as the first barrier against viral injury by affecting iron metabolism. Moreover, a few recent studies have proposed the combination of protease inhibitors for therapeutic use against SARS-CoV-2 infection, highlighting the role of viral protease in virus infectivity. In this regard, this review focuses on the analysis, through literature and docking studies, of a number of natural products able to counteract SARS-CoV-2 infection, acting both as iron chelators and protease inhibitors.

Interactions between free and bound antioxidants under different conditions in food systems

This review aimed to give comprehensive information about the interactions between free and bound antioxidants naturally found in different food matrices. In this context, firstly, the free and bound antioxidant terms are defined; their place in the daily diet, the path they follow in the body and their characteristics are explained. Factors affecting the interactions have been revealed as a result of the compilation of studies conducted until today, related to bound and free antioxidant interactions. Accordingly, it was observed that many factors such as reaction environment, concentration, pH, chemical structure, source and antioxidant/prooxidant nature of the compounds were effective on interactions. It has been emphasized that the interactions between free and bound antioxidants have a dynamic balance that can easily change under the influence of various factors, which in turn needs the interactions to be handled specifically for each case.

In Vitro Pro-Glycative Effects of Resveratrol and Caffeic Acid

Resveratrol and caffeic acid belong to plant polyphenols and are known for their antioxidant effects. The aim of our research was to study their impact on Maillard reaction. This one occurs when the reducing saccharides react with amino groups of biomolecules including proteins, alter their protein conformation and transform to the variety of advanced glycation end products (AGEs). AGEs exhibit browning and generate fluorescence. There exist expectations that this oxidative protein glycosylation could be prevented by antioxidants. In this study, we incubated bovine serum albumin (BSA) with glucose for 7 days at 37°C and measured characteristic fluorescence and UV absorbance of the formed AGEs. Surprisingly, resveratrol and caffeic acid enhanced transformation of BSA to glycation products, which was confirmed either when cupric Cu(II) or ferric Fe(III) ions in nanomolar concentration were added to the system as pro-oxidant agent.

Beyond the Antioxidant Activity of Dietary Polyphenols in Cancer: the Modulation of Estrogen Receptors (ERs) Signaling

The potential "health benefits" of dietary polyphenols have been ascribed to their direct antioxidant activity and their impact on the regulation of cell and tissue redox balance. However, because of the relative poor bioavailability of many of these compounds, their effects could not be easily explained by the antioxidant action, which may occur only at high circulating and tissue concentrations. Therefore, many efforts have been put forward to clarify the molecular mechanisms underlining the biological effect of polyphenols in physiological and pathological conditions. Polyphenols' bioavailability, metabolism, and their effects on enzyme, membrane, and/or nuclear receptors and intracellular transduction mechanisms may define the overall impact of these compounds on cancer risk and progression, which is still debated and not yet clarified. Polyphenols are able to bind to estrogen receptor α (ERα) and β (ERβ), and therefore induce biological effects in human cells through mimicking or inhibiting the action of endogenous estrogens, even at low concentrations. In this work, the role and effects of food-contained polyphenols in hormone-related cancers will be reviewed, mainly focusing on the different polyphenols' mechanisms of action with particular attention on their estrogen receptor-based effects, and on the consequences of such processes on tumor progression and development.

Honey protects against wings posture error and molecular changes related to mitochondrial pathways induced by hypoxia/reoxygenation in adult Drosophila melanogaster

We conducted an investigation to evaluate the effects of Brazilian Pampa biome honey and its major phenolic compounds on the development of an erected wings posture phenotype and related mitochondrial aspects induced by Hypoxia/Reoxygenation (H/R) in Drosophila melanogaster. Flies were pre-treated for 3 days with a 10% honey solution and different concentrations of caffeic acid and ρ-coumaric acid and then submitted to hypoxia for 3 h. We observed that after reoxygenation, some flies acquired an erected wings posture and that this feature may be related to mortality. In addition, H/R induced down-regulation of ewg mRNA expression, which could be associated to the observed complex phenotype. H/R also caused a dysregulation in opa1-like, ldh and diap genes expression and reduced O₂ fluxes in flie's mitochondria. Honey mitigated opa1-like mRNA expression changes provoked by H/R. Differently from honey, caffeic and ρ-coumaric acids displayed no protective effects. In conclusion, we report for the first time the protective effects of honey against complex phenotypes and mitochondrial changes induced by H/R in adult flies.

The Inhibition Effect of Cell DNA Oxidative Damage and LDL Oxidation by Bovine Colostrums

In the present study, we investigated the effect of bovine colostrums on inhibition of DNA oxidative damage and low density lipoprotein (LDL) oxidation in vitro. Results showed that whey and skimmed milk exhibited not only higher inhibitory activities of oxidative damage of deoxyribose but also an inhibitory effect on the breakdown of supercoiled DNA into open circular DNA and linear DNA. The quantities of 8-OH-2'-dG formed under whey, caseins and skimmed milk treatment were 0.24, 0.24 and 1.24 μg/mL, respectively. The quantity of malondialdehyde formed through LDL oxidation induced by copprous ion was significantly decreased as colostrums protein solutions were added, in which whey and caseins led to a more significant decrease than skimmed milk. The formation of conjugated dienes could be inhibited by treatment with colostrums protein solutions. Whey exhibited the longest lag time of conjugated dienes formation among the colostrums proteins. The lag time of the whey was 2.33 times that of the control. From the results of foregoing, the bovine colostrums protein has potential value in the inhibition of DNA oxidation damage and LDL oxidation.

Reducing Compounds Equivocally Influence Oxidation during Digestion of a High-Fat Beef Product, which Promotes Cytotoxicity in Colorectal Carcinoma Cell Lines

We studied the formation of malondialdehyde, 4-hydroxy-nonenal, and hexanal (lipid oxidation products, LOP) during in vitro digestion of a cooked low-fat and high-fat beef product in response to the addition of reducing compounds. We also investigated whether higher LOP in the digests resulted in a higher cyto- and genotoxicity in Caco-2, HT-29 and HCT-116 cell lines. High-fat compared to low-fat beef digests contained approximately 10-fold higher LOP concentrations (all P < 0.001), and induced higher cytotoxicity (P < 0.001). During digestion of the high-fat product, phenolic acids (gallic, ferulic, chlorogenic, and caffeic acid) displayed either pro-oxidant or antioxidant behavior at lower and higher doses respectively, whereas ascorbic acid was pro-oxidant at all doses, and the lipophilic reducing compounds (α-tocopherol, quercetin, and silibinin) all exerted a clear antioxidant effect. During digestion of the low-fat product, the hydrophilic compounds and quercetin were antioxidant. Decreases or increases in LOP concentrations amounted to 100% change versus controls.

Antioxidant Activity of Caffeic Acid against Iron-Induced Free Radical Generation--A Chemical Approach

Caffeic acid (CA) is a phenolic compound widely found in coffee beans with known beneficial effects in vivo. Many studies showed that CA has anti-inflammatory, anti-mutagenic, antibacterial and anti-carcinogenic properties, which could be linked to its antioxidant activity. Taking in consideration the reported in vitro antioxidant mechanism of other polyphenols, our working hypothesis was that the CA antioxidant activity could be related to its metal-chelating property. With that in mind, we sought to investigate the chemical antioxidant mechanism of CA against in vitro iron-induced oxidative damage under different assay conditions. CA was able to prevent hydroxyl radical formation promoted by the classical Fenton reaction, as determined by 2-deoxyribose (2-DR) oxidative degradation and DMPO hydroxylation. In addition to its ability to prevent hydroxyl radical formation, CA had a great inhibition of membrane lipid peroxidation. In the lipid peroxidation assays CA acted as both metal-chelator and as hydrogen donor, preventing the deleterious action promoted by lipid-derived peroxyl and alkoxyl radicals. Our results indicate that the observed antioxidant effects were mostly due to the formation of iron-CA complexes, which are able to prevent 2-DR oxidation and DMPO hydroxylation. Noteworthy, the formation of iron-CA complexes and prevention of oxidative damage was directly related to the pH of the medium, showing better antioxidant activity at higher pH values. Moreover, in the presence of lipid membranes the antioxidant potency of CA was much higher, indicating its enhanced effectiveness in a hydrophobic environment. Overall, our results show that CA acts as an antioxidant through an iron chelating mechanism, preventing the formation of free hydroxyl radicals and, therefore, inhibiting Fenton-induced oxidative damage. The chemical properties of CA described here—in association with its reported signaling effects—could be an explanation to its beneficial effects observed in vivo.

Interactions of black tea polyphenols with human gut microbiota: implications for gut and cardiovascular health

Epidemiologic studies have convincingly associated consumption of black tea with reduced cardiovascular risk. Research on the bioactive molecules has traditionally been focused on polyphenols, such as catechins. Black tea polyphenols (BTPs), however, mainly consist of high-molecular-weight species that predominantly persist in the colon. There, they can undergo a wide range of bioconversions by the resident colonic microbiota but can in turn also modulate gut microbial diversity. The impact of BTPs on colon microbial composition can now be assessed by microbiomics technologies. Novel metabolomics platforms coupled to de novo identification are currently available to cover the large diversity of BTP bioconversions by the gut microbiota. Nutrikinetic modeling has been proven to be critical for defining nutritional phenotypes related to gut microbial bioconversion capacity. The bioactivity of circulating metabolites has been studied only to a certain extent. Bioassays dedicated to specific aspects of gut and cardiovascular health have been used, although often at physiologically irrelevant concentrations and with limited coverage of relevant metabolite classes and their conjugated forms. Evidence for cardiovascular benefits of BTPs points toward antiinflammatory and blood pressure-lowering properties and improvement in platelet and endothelial function for specific microbial bioconversion products. Clearly, more work is needed to fill in existing knowledge gaps and to assess the in vitro and in vivo bioactivity of known and newly identified BTP metabolites. It is also of interest to assess how phenotypic variation in gut microbial BTP bioconversion capacity relates to gut and cardiovascular health predisposition.

Caffeic acid treatment alters the extracellular adenine nucleotide hydrolysis in platelets and lymphocytes of adult rats

This study evaluated the effects of caffeic acid on ectonucleotidase activities such as NTPDase (nucleoside triphosphate diphosphohydrolase), Ecto-NPP (nucleotide pyrophosphatase/phosphodiesterase), 5'-nucleotidase and adenosine deaminase (ADA) in platelets and lymphocytes of rats, as well as in the profile of platelet aggregation. Animals were divided into five groups: I (control); II (oil); III (caffeic acid 10 mg/kg); IV (caffeic acid 50 mg/kg); and V (caffeic acid 100 mg/kg). Animals were treated with caffeic acid diluted in oil for 30 days. In platelets, caffeic acid decreased the ATP hydrolysis and increased ADP hydrolysis in groups III, IV and V when compared to control (P<0.05). The 5'-nucleotidase activity was decreased, while E-NPP and ADA activities were increased in platelets of rats of groups III, IV and V (P<0.05). Caffeic acid reduced significantly the platelet aggregation in the animals of groups III, IV and V in relation to group I (P<0.05). In lymphocytes, the NTPDase and ADA activities were increased in all groups treated with caffeic acid when compared to control (P<0.05). These findings demonstrated that the enzymes were altered in tissues by caffeic acid and this compound decreased the platelet aggregation suggesting that caffeic acid should be considered a potentially therapeutic agent in disorders related to the purinergic system.

The proglycation effect of caffeic acid leads to the elevation of oxidative stress and inflammation in monocytes, macrophages and vascular endothelial cells

In this study, the effects of phenolic acids [caffeic acid (CA), ferulic acid, m-coumaric acid, and chlorogenic acid] on methylglyoxal (MG)-induced protein glycation were investigated in vitro. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and advanced glycation end products (AGEs)-specific fluorescence showed that MG-mediated protein modification was enhanced dose-dependently by CA (P<.05), whereas α-lipoic acid, glutathione and EDTA inhibited these changes. Electron paramagnetic resonance spectra showed that CA increased reactive oxygen species (ROS) production during glycation, suggesting the proglycation mechanism of CA is associated with its pro-oxidative properties. Additionally, fetal bovine serum (FBS) was utilized as the source of target proteins for evaluating the effects of CA in cells. Differential glycation of FBS samples was performed by incubating FBS with MG, CA or aminoguanidine (AG, an AGE inhibitor). FBS incubated with MG and CA (MG/CA-FBS) evoked the greatest deleterious responses, as follows: (1) inducing proinflammatory tumor necrosis factor (TNF)-α and interleukin-1β expression and ROS production in monocytic THP-1 cells, (2) stimulating TNF-α secretion in RAW 264.7 macrophages and (3) causing oxidative DNA damage and inducing the expression of receptor for AGEs (RAGE), intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 in human umbilical vein endothelial cells. Furthermore, adhesion and transendothelial migration of monocytes were also significantly increased by MG/CA-FBS treatment compared to MG-FBS (P<.05). In conclusion, our data show that CA exhibits pro-oxidative and pro-glycative effects during the glycation process, suggesting a detrimental role for CA under high-glycotoxin conditions.

Coffee intake can promote activity of antioxidant enzymes with increasing MDA level and decreasing HDL-cholesterol in physically trained rats

This study investigated the effect of coffee intake and exercise on the antioxidative activity and plasma cholesterol profile of physically trained rats while they were exercising. Forty eight rats were under either the control diet with water (C) or control diet with coffee (CF) and at the same time they were given physical training for 4 weeks. In terms of physical training, the rats were exercised on a treadmill for 30 minutes everyday. At the end of 4 weeks, animals in each dietary group were subdivided into 3 groups: before-exercise (BE); during-exercise (DE); after-exercise (AE). Animals in the DE group were exercised on a treadmill for one hour, immediately before being sacrificed. Animals in the AE group were allowed to take a rest for one hour after exercise. TG levels were significantly high in coffee intake group than in control group. Also TG level of AE group was significantly higher than that of BE group. Exercise and coffee-exercise interaction effects were significant in total cholesterol (P = 0.0004, 0.0170). The AE of coffee intake group showed highest total cholesterol levels. HDL-cholesterol was significantly lower in coffee intake group than in control group. Coffee, exercise, and coffee-exercise interaction effects were significant in SOD (P = 0.0001, 0.0001, and 0.0001). The AE and BE of coffee intake group showed higher SOD levels than the other four groups. Catalase activities were significantly higher in coffee intake group than control group. No significant main effect was found in GSH/GSSG. Coffee, exercise, and coffee-exercise interaction effects were significant in MDA levels (P = 0.0464, 0.0016, and 0.0353). The DE and AE of coffee intake group and the DE of control group showed higher MDA levels than the BE of control group. Therefore, coffee intake can promote activities of antioxidant enzyme but it also increases MDA and decreases HDL-cholesterol in physically trained rats.

The polyphenolics in the aqueous extract of Psidium guajava kinetically reveal an inhibition model on LDL glycation

Guava [Psidium guajava L. (Myrtaceae)] budding leaf extract (PE) has shown tremendous bioactivities. Previously, we found seven major compounds in PE, i.e., gallic acid, catechin, epicatechin, rutin, quercetin, naringenin, and kaempferol. PE showed a potentially active antiglycative effect in an LDL (low density lipoprotein) mimic biomodel, which can be attributed to its large content of polyphenolics. The glycation and antiglycative reactions showed characteristic distinct four-phase kinetic patterns. In the presence of PE, the kinetic coefficients were 0.000438, 0.000060, 0.000, and -0.0001354 ABS-mL/mg-min, respectively, for phases 1 to 4. Computer simulation evidenced the dose-dependent inhibition model. Conclusively, PE contains a large amount of polyphenolics, whose antiglycative bioactivity fits the inhibition model.

Inactivation of PadR, the repressor of the phenolic acid stress response, by molecular interaction with Usp1, a universal stress protein from Lactobacillus plantarum, in Escherichia coli

The phenolic acid decarboxylase gene padA is involved in the phenolic acid stress response (PASR) in gram-positive bacteria. In Lactobacillus plantarum, the padR gene encodes the negative transcriptional regulator of padA and is cotranscribed with a downstream gene, usp1, which encodes a putative universal stress protein (USP), Usp1, of unknown function. The usp1 gene is overexpressed during the PASR. However, the role and the mechanism of action of the USPs are unknown in gram-positive bacteria. Therefore, to gain insights into the role of USPs in the PASR; (i) a usp1 deletion mutant was constructed; (ii) the two genes padR and usp1 were coexpressed with padA under its own promoter as a reporter gene in Escherichia coli; and (iii) molecular in vitro interactions between the PadR, Usp1, and the padA promoter were studied. Although the usp1 mutant strain retained phenolic acid-dependent PAD activity, it displayed a greater sensitivity to strong acidic conditions compared to that of the wild-type strain. PadR cannot be inactivated directly by phenolic acid in E. coli recombinant cultures but is inactivated by Usp1 when the two proteins are coexpressed in E. coli. The PadR inactivation observed in recombinant E. coli cells was supported by electrophoretic mobility shift assays. Although Usp1 seems not to be absolutely required for the PASR, its capacity to inactivate PadR indicates that it could serve as an important mediator in acid stress response mechanisms through its capacity to interact with transcriptional regulators.

5-caffeoylquinic acid and caffeic acid down-regulate the oxidative stress- and TNF-alpha-induced secretion of interleukin-8 from Caco-2 cells

Although chlorogenic acid (CHA) easily reaches a millimolar level in the gastrointestinal tract because of its high concentration in coffee and fruits, its effects on intestinal epithelial cells have been little reported. We investigated in this study the down-regulative effects of 5-caffeoylquinic acid (CQA), the predominant isomer of CHA, on the H(2)O(2-) or TNF-alpha-induced secretion of interleukin (IL)-8, a central pro-inflammatory chemokine involved in the pathogenesis of inflammatory bowel diseases, in human intestinal epithelial Caco-2 cells. After the cells had been pre- and simultaneously treated with CQA, the oversecretion of IL-8 and overexpression of its mRNA induced by H(2)O(2) were significantly suppressed in a dose-dependent manner in the range of 0.25-2.00 mmol/L. We further found that a metabolite of CQA, caffeic acid (CA), but not quinic acid, significantly inhibited the H(2)O(2)-induced IL-8 secretion and its mRNA expression in the same dose-dependent manner. Both CQA and CA suppressed the TNF-alpha-induced IL-8 secretion as well. Caffeic acid at 2.00 mmol/l was able to absolutely block the H(2)O(2)- or TNF-alpha-induced oversecretion of IL-8 in Caco-2 cells. However, CQA and CA did not suppress the TNF-alpha-induced increase in the IL-8 mRNA expression, indicating that the suppressive mechanisms are different between TNF-alpha-induced and H(2)O(2)-induced IL-8 production models. These results suggest that the habit of drinking coffee and/or eating fruits with a high CHA content may be beneficial to humans in preventing the genesis of inflammatory bowel diseases.

Efficacy of caffeic acid in preventing nickel induced oxidative damage in liver of rats

Nickel (Ni), a major environmental pollutant, is known for its wide toxic manifestations. In the present study caffeic acid (CA), one of the most commonly occurring phenolic acids in fruits, grains and dietary supplements, was evaluated for its protective effect against the Ni induced oxidative damage in liver. In this investigation, Ni (20 mg/kg body weight) was administered intraperitoneally for 20 days to induce toxicity. CA was administered orally (15, 30 and 60 mg/kg body weight) for 20 days with intraperitoneal administration of Ni. Ni induced liver damage was clearly shown by the increased activities of serum hepatic enzymes namely aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), gamma glutamyl transferase (GGT) and lactate dehydrogenase (LDH) along with increased elevation of lipid peroxidation indices (thiobarbituric reactive acid substances (TBARS) and lipid hydroperoxides). The toxic effect of Ni was also indicated by significantly decreased levels of enzymatic (superoxide dismutase (SOD), catalase (CAT) glutathione peroxidase (GPx) and glutathione S-transferase (GST)) and non-enzymatic antioxidants (glutathione (GSH), vitamin C and vitamin E). CA administered at a dose of 60 mg/kg body weight significantly reversed the activities of hepatic marker enzymes to their near normal levels when compared with other two doses. In addition, CA significantly reduced lipid peroxidation and restored the levels of antioxidant defense in the liver. All these changes were supported by histological observations. The results indicate that CA may be beneficial in ameliorating the Ni induced oxidative damage in the liver of rats.

Phenolic compounds, organic acids profiles and antioxidative properties of beefsteak fungus (Fistulina hepatica)

The phenolic compounds and the organic acids composition of the edible beefsteak fungus Fistulina hepatica was determined by HPLC/DAD and HPLC/UV, respectively. The results showed a profile composed by five phenolic compounds (caffeic, p-coumaric and ellagic acids, hyperoside and quercetin) and six organic acids (oxalic, aconitic, citric, malic, ascorbic and fumaric acids). The quantification of the identified compounds revealed that ellagic acid (ca. 49.7%) and malic acid (ca. 57.9%) are the main compounds in this species. In a general way the phenolic profile revealed to be more constant than the organic acids one and could be more useful for the quality control of the species. Beefsteak fungus was also investigated for its capacity to act as a scavenger of DPPH() radical and reactive oxygen species (superoxide radical, hydroxyl radical and hypochlorous acid). Good results were obtained against DPPH in a concentration-dependent manner. Beefsteak fungus also displayed good activity against superoxide radical, achieved by its capacity to act as both scavenger and xanthine oxidase inhibitor. A prooxidant effect was noticed for hydroxyl radical, which may be due to its capacity for iron ions reduction. Little ability for iron chelation was also observed. Beefsteak fungus showed a weak protective effect against hypochlorous acid.

Targeted natural product isolation guided by HPLC-SPE-NMR: constituents of Hubertia species

The hyphenated technique, high-performance liquid chromatography-solid-phase extraction-nuclear magnetic resonance spectroscopy (HPLC-SPE-NMR), has been applied for rapid identification of novel natural products in crude extracts of Hubertia ambavilla and Hubertia tomentosa. The technique allowed full or partial identification of all major extract constituents and demonstrated the presence of unusual quinic acid derivatives containing the (1-hydroxy-4-oxocyclohexa-2,5-dienyl)acetyl residue that exhibit strongly coupled ABXY patterns, the parameters of which were obtained by spin simulations. Using homo- and heteronuclear 2D NMR data acquired in the HPLC-SPE-NMR mode, complete structure determination of three new natural products, i.e., 3,5-di-O-caffeoyl-4-O-[(1-hydroxy-4-oxocyclohexa-2,5-dienyl)acetyl]quinic acid (1), its 2-hydroxy derivative (2), and 3,5-di-O-caffeoyl-4-O-[(4-hydroxyphenyl)acetyl]quinic acid (3), was performed. Finally, targeted isolation of 1 was achieved by SPE fractionation and preparative HPLC, followed by evaluation of its antioxidant and antimicrobial activity. In contrast to chlorogenic acid and 3,5-di-O-caffeoylquinic acid, which act as antioxidants, compound 1 proved at the same conditions to possess prooxidant activity in an assay evaluating the oxidation of human low-density lipoprotein induced by Cu(2+).

Coffee consumption protects human lymphocytes against oxidative and 3-amino-1-methyl-5H-pyrido[4,3-b]indole acetate (Trp-P-2) induced DNA-damage: Results of an experimental study with human volunteers

Aim of the study was to investigate the impact of coffee on DNA-stability in humans. DNA-damage was monitored in lymphocytes of eight individuals with single cell gel electrophoresis assays before and after consumption of 600 ml coffee (400 ml paper filtered and 200 ml metal filtered/d) for five days. Under standard conditions, no alteration of DNA-migration was seen, but a strong reduction of DNA-migration attributable to endogenous formation of oxidised purines and pyrimidines was detected with restriction enzymes; furthermore DNA-damage caused by reactive oxygen radicals (H2O2 treatment) and by the heterocyclic aromatic amine 3-amino-1-methyl-5H-pyrido[4,3-b]indole-acetate was significantly reduced after coffee consumption by 17% and 35%, respectively. Also in in vitro experiments, inhibition of H2O2 induced DNA-damage was observed with coffee at low concentrations (<or= 25 microl/ml) whereas the diterpenoids cafestol and kahweol caused only marginal effects indicating that the effects of coffee are due to scavenging effects of other constituents. Enzyme measurements showed that additionally induction of antioxidant enzymes may play a role: while the activity of glutathione peroxidase was only marginally increased after coffee consumption, a significant (38%) increase of superoxide dismutase activity was detected. Comparisons with results of earlier studies suggest that coffee consumption may prevent oxidative DNA-damage to a higher extent as diets enriched in fruits and vegetables.

Prooxidant activity of hydroxycinnamic acids on DNA damage in the presence of Cu(II) ions: mechanism and structure-activity relationship

The prooxidant effect of hydroxycinnamic acids (HCAs), i.e., caffeic acid (CaA), chlorogenic acid (ChA), sinapic acid (SA), ferulic acid (FA), 3-hydroxycinnamic acid (3-HCA) and 4-hydroxycinnamic acid (4-HCA) on supercoiled pBR322 plasmid DNA strand breakage and calf thymus DNA damage in the presence of Cu(II) ions has been studied. It was found that the compounds bearing ortho-dihydroxyl group (CaA and ChA) or bearing 4-hydroxy-3-methoxyl group (SA and FA) exhibited remarkably higher activity in the DNA damage than the ones bearing no such functionalities. The good correlation between the DNA damaging activity and the oxidative potential of the compounds indicates that the electron transfer between HCAs and Cu(II) plays a crucial role in the reaction. UV-Visible spectral changes demonstrated that CaA or ChA can chelate with Cu(II) as a bidentate ligand, hence facilitating intramolecular electron transfer between CaA or ChA and Cu(II). The involvement of reactive oxygen species (ROS) and Cu(I) ions in the DNA damage were affirmed by the inhibition of DNA breakage using mannitol, glutathione (GSH), catalase and bathocuproinedisulfonic acid (BCDS). These results may have important implications regarding the proposed mechanism of apoptosis induced by phenol and endogenous metal ions.

Low-density lipoprotein, collagen, and thrombin models reveal that Rosemarinus officinalis L. exhibits potent antiglycative effects

Using the low-density lipoprotein (LDL), collagen, and thrombin models, we report here that the rosemary extracts (REs), either the aqueous (REw) or the acetonic (REA), all possessed many antiglycation-related features, and the effective concentrations required were as follows: 0.1 mg/mL for suppressing the relative electrophoretic mobility, 1.3 microg/mL for anticonjugated diene induction, 0.5 mg/mL for inhibition of thiobarbituric acid reactive substances production, 0.1 mg/mL for AGEs (advanced glycation end products) formation, 0.1 mg/mL to block glucose incorporation, and 0.05 mg/mL as an effective anti-antithrombin III. Using high-performance liquid chromatography/mass spectrometry, we identified five major constituents among eight major peaks, including rosmarinic acid, carnosol, 12-methoxycarnosic acid, carnosic acid, and methyl carnosate. In the LDL model, REA was proven to be more efficient than REw; yet, the reverse is true for the collagen and the thrombin III models, the reason of which was ascribed to the higher lipid-soluble antioxidant content (such as rosmarinic acid, carnosol, carnosic acid, 12-methoxycarnosic acid and methyl carnosate) in REA than in REw and the different surface lipid characteristics between LDL and collagen; although to act as anti-AGEs, both extracts were comparable. To assist the evidence, a larger 2,2-diphenyl-1-picrylhydrazyl radical scavenging capability with less total polyphenolic content was found in REA. We conclude that rosemary is an excellent multifunctional therapeutic herb; by looking at its potential potent antiglycative bioactivity, it may become a good adjuvant medicine for the prevention and treatment of diabetic, cardiovascular, and other neurodegenerative diseases.

Non-natural cinnamic acid derivatives as substrates of cinnamate 4-hydroxylase

Cinnamate 4-hydroxylase (C4H), a monooxygenase in the plant phenylpropanoid pathway, was assayed for its ability to hydroxylate 29 substrate analogues. Nine of the tested analogues with various aromatic side chains, including 3-coumaric acid, were metabolized by C4H. Seven products from these reactive analogues were characterized using LC/MS, 1H NMR and 13C NMR spectroscopic analysis. For example, caffeic acid was the product of 3-coumaric acid. The products 4-hydroxy-2-chlorocinnamic acid and 4-hydroxy-2-ethoxycinnamic acid are novel compounds that have not been previously reported. The kinetic parameters of C4H towards these analogues were determined.

Kinetic analysis on the sensitivity of glucose- or glyoxal-induced LDL glycation to the inhibitory effect of Psidium guajava extract in a physiomimic system

Experimentation with a physiomimic system and kinetic analysis exhibited four distinct reaction phases in LDL glycation despite of the type of inducer: glucose or glyoxal. LDL glycation was more sensitive to a status of hyperglycemia (such as 400 mg glucose/100 mL) as evidenced by the reaction order of 0.53. Glucose reacted intensively in the Initial Phase (reaction period 0-2h) which was identified to result from a parallel mechanism involving both the direct Schiff's product formation and the auto-oxidative cleavages. In contrast, a physiological level of glyoxal revealed merely a reaction order of only 0.09, implicitly indicating a far less sensitive glycation which can be attributed to a mechanism proceeding simply through a molecular Schiff's reaction. On treatment with Psidium guajava L. aqueous extract (PE) (0.01-0.625 mg/mL), a rather unique and significant inhibitory characteristic on LDL glycation was observed with a dose-dependent manner. We attributed such an effect of PE to its distinct abundance of polyphenolic content (165.61+/-10.39 mggallic acid equivalent (GAE)/g). Conclusively, PE is an excellent anti-LDL glycative agent whose potential therapeutic uses can be extended to the prevention of a variety of cardiovascular and neurodegenerative diseases associated with glycations.

The active components and the pharmacological multi-target principle of STW 5 (Iberogast)

The therapeutic equivalence of the multi-herbal drug combination STW 5 (Iberogast) with two synthetic standard drugs can be explained by an additive or overadditive pharmacological synergism. A review of the different chemical constituents contained in this fixed combination of nine herbal drug extracts and their dominant mechanisms of action shows that they correlate very well with the clinically relevant overall pharmacological profile of the multi-herbal drug combination. This comprises modulatory effects on gastro-intestinal motility, anti-inflammatory action, inhibitory effects on gastric acid production and anti-oxidative and radical-inhibiting properties. As a multi-drug preparation with a multitude of therapeutic targets relevant in functional gastrointestinal diseases, its pharmacological profile of action in accordance with the multi-target principle.

Inhibitory effect of some selected nutraceutic herbs on LDL glycation induced by glucose and glyoxal

Anti-LDL glycative agents were investigated using aqueous extracts of Psidium guajava L. (PE), Toona sinensis Roem. (TE), Momordica charantia L. (ME) and Graptopetalum paragugayene E. Walther (GE). Concentrations of extracts 0.01-0.625 mg/mL, low density lipoprotein (LDL; 100 microg protein/mL) and inducers glucose (400 mM) and glyoxal (2.5 mM) were incubated at 37 degrees C. Evaluation parameters involved the thiobarbituric acid reactive substances (TBARS), conjugated dienes (CD), relative electrophoretic mobility (REM), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capability and total polyphenolic content. Results for anti-TBARS efficiency (in%) were PE (75.77), TE (75.10), ME (68.81) and GE (19.81) at 0.5 mg/mL, respectively, when induced by glucose; 36.68, 35.60, 32.62 and inactive, respectively, by glyoxal. The lag times for CD formation (in min) were: 289 and 125 by PE and TE, respectively, comparing to the control (45). REM was 1.6 with respect to PE (0.1 mg/mL) compared to the control (4.2). PE at 0.01 mg/mL effectively inhibited with 63.45% efficiency on AGEs induced by glucose. We conclude that PE virtually is a potent antiglycative agent, which can be of great value in the preventive glycation-associated cardiovascular and neurodegenerative diseases.

Role of NADPH oxidase-mediated generation of reactive oxygen species in the mechanism of apoptosis induced by phenolic acids in HepG2 human hepatoma cells

Although plant-derived phenolic acids have been reported to have anti-cancer activity, the exact mechanism is not completely understood. In this study, we investigated the role for reactive oxygen species (ROS) as a mediator of the apoptosis induced by caffeic acid (CA) and ferulic acid (FA), common phenolic acids in plants, in HepG2 human hepatoma cells. CA and FA reduced cell viability, and induced apoptotic cell death in a dose-dependent manner. In addition, they evoked a dose-related elevation of intracellular ROS. Treatment with various inhibitors of NADPH oxidase (diphenylene iodonium, apocynin, neopterine) significantly blunted both the generation of ROS and the induction of apoptosis induced by CA and FA. These results suggest that ROS generated through activation of NADPH oxidase may play an essential role in the apoptosis induced by CA and FA in HepG2 cells. These results further suggest that CA and FA may be valuable for the therapeutic management of human hepatomas.

Antioxidant activities of phenolic acids on ultraviolet radiation-induced erythrocyte and low density lipoprotein oxidation

The exposure of mammalian cells to UV light induces various deleterious responses. Some of the major harmful effects are DNA damage, cell membrane peroxidation, systemic immune suppression, and aging acceleration. Reactive oxygen species and free radicals are believed to be largely responsible for some of the deleterious effects of UV upon cells. Typical administration of antioxidants has recently proved to represent a successful strategy for protecting the cells against UV-mediated oxidative damage. The objective of this study was to investigate the inhibitory effect of phenolic acids (caffeic acid, ferulic acid, gallic acid, and protocatechuic acid) on oxidative damage in human erythrocytes and low-density lipoprotein (LDL) induced by UVB radiation. The results revealed that the thiobarbituric acids reactive substances induced by UVB were decreased from 2.78 to 0.12-0.89 nmol MDA/mg protein in erythrocyte ghost and from 0.72 to 0.14-0.43 nmol MDA/mg protein in LDL by the addition of phenolic acids (100 muM). Caffeic acid, ferulic acid, and gallic acid exhibited over 85 and 60% inhibitory effect toward UVB-induced oxidation in erythrocytes and LDL, respectively. Phenolic acids, especially gallic acid, could maintain the normal glutathione levels and glutathione peroxidase activity in hemolysate from erythrocytes that were exposed to UVB radiation in comparison with untreated control. The results indicate that the antioxidant activities of caffeic acid and ferulic acid play a potential role in protection against UVB oxidative damage to human erythrocytes and LDL.

Effect of 3,4-di(OH)-cinnamate synthetic derivative on plasma and hepatic cholesterol level and antioxidant enzyme activities in high cholesterol-fed rats

The effect of 3,4-di(OH)-phenylpropionic acid (L-phenylalanine methyl ester) amide (SL-1063), a synthetic derivative of 3,4-di(OH)-cinnamate, on the cholesterol metabolism and antioxidant enzyme system was examined in rats. Diets that included either SL-1063 (0.046%, w/w) or lovastatin (0.02%, w/w) as a supplement, plus 1 g cholesterol/100 g diet were fed to rats ad libitum for 5 weeks. The total plasma cholesterol and triglyceride levels were significantly lowered by the SL-1063 supplement compared to the control group. Meanwhile, the levels of plasma HDL-cholesterol and ratio of HDL-cholesterol/total cholesterol (%) were significantly higher in the SL-1063 group than in the control group. However, the lovastatin supplement did not affect the plasma lipid level. The hepatic cholesterol level and 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase activity were significantly lowered in the lovastatin group compared to the SL-1063 group; however, the hepatic triglyceride level did not differ among the groups. The activity of hepatic acyl CoA: cholesterol acyltransferase (ACAT), the enzyme that catalyzes hepatic cholesterol esterification, was significantly lower in the lovastatin and SL-1063 groups than in the control group. Furthermore, the SL-1063 supplement elevated the excretion of fecal sterols. As regards the hepatic antioxidant enzyme system, the superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and glutathione reductase (GR) activities were all significantly higher in the SL-1063 group compared to the control group, whereas only the GR activity was significantly increased by the lovastatin supplement. No marked difference in the GSH levels and glucose-6-phosphate dehydrogenase (G6PD) activities was observed among the groups. The levels of plasma and hepatic thiobarbituric acid reactive substances (TBARS) were lowered by the SL-1063 supplement compared to the control group. Accordingly, the current results suggest that SL-1063, a synthetic derivative of 3,4-di(OH)-cinnamate, is effective in lowering the plasma lipids and improving the antioxidant enzyme system.

Bioactivity and analysis of biophenols recovered from olive mill waste

Biophenols have attracted increasing attention during the past few years due to their biological activities and natural abundance and are potential targets for the food and pharmaceutical industries. Olive mill waste (OMW) is rich in biophenols and typically contains 98% of the total phenols in the olive fruit, making value addition to OMW an attractive enterprise. The phenolic profile of OMW is complex, yet this complexity has not been fully exploited in the valorization of the waste. Most work on the bioactivity of OMW has focused on antioxidant and antimicrobial activities. The analytical techniques used to identify and quantify active biophenols are also reviewed.

Modification of N‐Acetyltransferases and Glutathione S‐Transferases by Coffee Components: Possible Relevance for Cancer Risk

Enzymes of xenobiotic metabolism are involved in the activation and detoxification of carcinogens and can play a pivotal role in the susceptibility of individuals toward chemically induced cancer. Differences in such susceptibility are often related to genetically predetermined enzyme polymorphisms but may also be caused by enzyme induction or inhibition through environmental factors or in the frame of chemopreventive intervention. In this context, coffee consumption, as an important lifestyle factor, has been under thorough investigation. Whereas the data on a potential procarcinogenic effect in some organs remained inconclusive, epidemiology has clearly revealed coffee drinkers to be at a lower risk of developing cancers of the colon and the liver and possibly of several other organs. The underlying mechanisms of such chemoprotection, modifications of xenobiotic metabolism in particular, were further investigated in rodent and in vitro models, as a result of which several individual chemoprotectants out of the >1000 constituents of coffee were identified as well as some strongly metabolized individual carcinogens against which they specifically protected. This chapter discusses the chemoprotective effects of several coffee components and whole coffee in association with modifications of the usually protective glutathione-S-transferase (GST) and the more ambivalent N-acetyltransferase (NAT). A key role is played by kahweol and cafestol (K/C), two diterpenic constituents of the unfiltered beverage that were found to reduce mutagenesis/tumorigenesis by strongly metabolized compounds, such as 2-amino-1-methyl-6-phenylimidazo-[4,5-b]pyridine, 7,12-dimethylbenz[a]anthracene, and aflatoxin B(1), and to cause various modifications of xenobiotic metabolism that were overwhelmingly beneficial, including induction of GST and inhibition of NAT. Other coffee components such as polyphenols and K/C-free coffee are also capable of increasing GST and partially of inhibiting NAT, although to a somewhat lesser extent.

Anti- and pro-oxidant effects of quercetin in copper-induced low density lipoprotein oxidation. Quercetin as an effective antioxidant against pro-oxidant effects of urate

We recently reported that, depending on its concentration, urate is either a pro- or an antioxidant in Cu(2+)-induced low-density lipoprotein (LDL) oxidation. We also previously demonstrated an antioxidant synergy between urate and some flavonoids in the Cu(2+)-induced oxidation of diluted serum. As a result, the effect of the flavonoid quercetin on the Cu(2+)-induced oxidation of isolated LDL has been studied either in the presence or absence of urate. We demonstrate that, like urate, quercetin alone, at low concentration, exhibits a pro-oxidant activity. The pro-oxidant behavior depends on the Cu(2+) concentration but it is not observed at high Cu(2+) concentration. When compared with urate, the switch between the pro- and the antioxidant activities occurs at much lower quercetin concentrations. As for urate, the pro-oxidant character of quercetin is related to its ability to reduce Cu(2+) with the formation of semioxidized quercetin and Cu(+) with an expected yield larger than that obtained with urate owing to a more favorable redox potential. It is also shown that the pro-oxidant activity of urate can be inhibited by quercetin. An electron transfer between quercetin and semioxidized urate leading to the repair of urate could account for this observation as suggested by recently published pulse radiolysis data. It is anticipated that the interactions between quercetin-Cu(2+)-LDL and urate, which are tightly controlled by their respective concentration, determine the balance between the pro- and antioxidant behaviors. Moreover, as already observed with other antioxidants, it is demonstrated that quercetin alone behaves as a pro-oxidant towards preoxidized LDL.

Metal-chelating properties, electrochemical behavior, scavenging and cytoprotective activities of six natural phenolics

Chelation, electrochemical, antioxidant and cytoprotective properties of six phenolics - cynarin and caffeic, chlorogenic, ferulic, protocatechuic and rosmarinic acids were studied on the following models: (i) chelation of transition metals, (ii) quenching of the diphenylpicrylhydrazyl radical (DPPH), (iii) determination of half-wave potential, (iv) erythrocytes or mitochondrial membranes damaged by tert-butyl hydroperoxide (tBH) and (v) a primary culture of rat hepatocytes intoxicated by Cu(II) and Fe(III) or tBH. All phenolics suppressed cell membrane damage induced by transition metals or tBH. The protectivity correlated with their capacity to bind transition metals, to scavenge DPPH radical and with the value of half-wave potentials. In in vitro assays, the most promising was rosmarinic acid.

Different antioxidant effects of polyphenols on lipid peroxidation and hydroxyl radicals in the NADPH-, Fe-ascorbate- and Fe-microsomal systems

Antioxidant and pro-oxidant effects of 14 naturally occurring polyphenols (PP) on rat liver microsomal lipid peroxidation (LP) and hydroxyl radical (*OH) production were studied in NADPH-dependent, 50 microM Fe(2+)-500 microM ascorbate (Fe-AA) or 50 microM Fe(2+) system, respectively. LP determined by the thiobarbituric acid method was inhibited in the NADPH system by flavonols and trans-resveratrol that were more effective than other flavonoids and derivatives of benzoic and cinnamic acid and were mostly more efficient than in the Fe-AA system. Inhibition of LP in the Fe system was higher by one order of magnitude than in the Fe-AA system. *OH production in the NADPH system, measured by formaldehyde production, was decreased by myricetin, fisetin and quercetin, but increased by kaempferol, morin and trans-resveratrol, indicating that z.rad;OH played a minor role in LP, which all of these PP inhibited. None of these PP at up to 40 microM concentration quenched *OH in the Fe-AA system. All tested PP, except trans-resveratrol and gentisic acid, spectrally interacted with Fe(2+) or Fe(3+), indicating formation of complexes or oxidation of PP. In contrast to the NADPH system we found no correlation between Fe(2+) chelation and inhibition of Fe-AA- or Fe-dependent LP indicating that iron chelation did not play a significant role in the two latter systems. It is concluded that the inhibition of LP by PP was apparently due to their hydrogen donating properties rather than chelation of iron.