Effects of phenolic propyl esters on the oxidative stability of refined sunflower oil

Antioxidant Enzyme System Modulation by Dietary Palm Oils, Palm Kernel Oil and Soybean Oil in Laying Hens

Palm-based oils (palm oil and kernel oil) and soybean oil have unique fatty acid and antioxidant profiles based on the compounds present in them. Hence, this study elucidated the antioxidant properties of crude palm oil (CPO), red palm oil (RPO), refined palm oil (RBD), palm kernel oil (PKO) and soybean oil (SBO) and the influence of dietary oils on blood lipid profiles, tissue fatty acid deposition and the expression of hepatic lipid and lipoprotein metabolism genes in laying hens. The oils were analyzed for color, beta-carotene, free fatty acid and acid value, phenolic content and lipid peroxidation. In an in vivo trial, 150 laying hens were allotted into five groups and supplemented with either CPO, RPO, RBD, PKO or SBO for 16 weeks. High antioxidant compounds present in palm oils help reduce the oxidation of oils. Dietary supplementation with palm oils, particularly CPO and RPO, contributed to the lower liver, serum and jejunal mucosal antioxidant enzyme activities. The antioxidant enzyme genes in the jejunal mucosa were downregulated in palm oils and PKO, but there was no difference between oils in antioxidant enzyme genes in the liver. In conclusion, dietary supplementation with oils with high antioxidant content contributed to protection against oxidation and was associated with a lower requirement for producing antioxidant enzymes.

Insight into structure-activity relationships of hydroxycinnamic acids modified porous starch: The effect of phenolic hydroxy groups

Antioxidant capacity of hydroxycinnamic acids-modified starch mainly depends on their chemical structure. Herein, cinnamic acid as well as meta-substituted and para-substituted cinnamic acid were selected for esterification with porous starch (labelled as CA@PS, m-CA@PS and p-CA@PS), with the successful formation of porous starch (labelled as PS) esters then confirmed by ¹H NMR, ¹³C solid-state NMR and FT-IR spectroscopy. Three PS esters with almost same degrees of substitution (DS) were obtained, and antioxidant assays, including DPPH radical scavenging, reducing power and hydroxyl radical scavenging tests, were subsequently used to evaluate the antioxidant activity of the esterified PS. Overall, CA@PS showed weak antioxidant activity because of the absence of phenolic hydroxy, while p-CA@PS displayed better antioxidant capacity. Because its conjugated structure offered the stronger electron-donating effect, that could enhance antioxidant capacity. Therefore, antioxidant capacity depended significantly on overall chemical structure, including numbers and substitution positions of phenolic hydroxy groups.

Investigation of the Effectiveness of a Vertical Centrifugation System Coupled with an Inert Gas Dosing Device to Produce Extra Virgin Olive Oil

Recent decades have seen the development of many effective and innovative technologies for extra virgin olive oil (EVOO) extraction. Various solutions have been proposed to remove dissolved oxygen from the oil. Given these issues, we have designed and developed a system that can be added to the centrifuges that are already used in the olive oil industry. The system reduces the oxidative impact through the release of a technical gas inside the separator, and consequently delays the onset of defects related to oxidation. The experiment tested different N2 flow rates, directly into the vertical centrifuge, and four levels of N2 were tested–a control level (no N2 injection); low (20 L/min), medium (40 L/min), and maximum (80 L/min)–in order to evaluate the effectiveness of this new technique on EVOO quality. This experiment demonstrates that the objectives have been achieved. The EVOO produced using our system had lower dissolved oxygen content with N2 injection, along with an enriched volatile fraction, and higher biophenol concentrations. The chemical analyses were confirmed by a sensory analysis, with an increase in fruity intensity and bitter taste.

Pyrazoles and Pyrazolines as Anti-Inflammatory Agents

The five-membered heterocyclic group of pyrazoles/pyrazolines plays important role in drug discovery. Pyrazoles and pyrazolines present a wide range of biological activities. The synthesis of the pyrazolines and pyrazole derivatives was accomplished via the condensation of the appropriate substituted aldehydes and acetophenones, suitable chalcones and hydrazine hydrate in absolute ethanol in the presence of drops of glacial acetic acid. The compounds are obtained in good yields 68-99% and their structure was confirmed using IR, ¹H-NMR, ¹³C-NMR and elemental analysis. The novel derivatives were studied in vitro for their antioxidant, anti-lipid peroxidation (AAPH) activities and inhibitory activity of lipoxygenase. Both classes strongly inhibit lipid peroxidation. Compound 2g was the most potent lipoxygenase inhibitor (IC₅₀ = 80 µM). The inhibition of the carrageenin-induced paw edema (CPE) and nociception was also determined, with compounds 2d and 2e being the most potent. Compound 2e inhibited nociception higher than 2d. Pyrazoline 2d was found to be active in a preliminary test, for the investigation of anti-adjuvant-induced disease (AID) activity. Pyrazoline derivatives were found to be more potent than pyrazoles. Docking studies of the most potent LOX inhibitor 2g highlight hydrophobic interactions with VAL126, PHE143, VAL520 and LYS526 and a halogen bond between the chlorine atom and ARG182.

Probing the structure-antioxidant activity relationships of four cinnamic acids porous starch esters

For investigation of antioxidant capacity relationship, four cinnamic acids (CNAs), including cinnamic (CA), ferulic (FA), p-coumaric (p-CA) and sinapic (SA) acids, were selected to modify porous starch (PS) with different degrees of substitution by esterification, respectively. The ester linkage of CNAs modified PS was confirmed by ¹H NMR, ¹³C solid-state NMR and FT-IR. The porous structure was maintained after esterification. Three in vitro antioxidant assays were applied to measure antioxidant capacities. The order of antioxidant capacity was SA@PS > FA@PS > p-CA@PS > CA@PS, due to the presence of phenolic hydroxyl groups with hydrogen donating abilities. Besides electron-donating group on ortho or para positions the benzene ring further enhances the hydrogen donating ability and the stability of hydroxyl radical. This study not only investigated the antioxidant mechanism of CNA modified starch derivatives but probed the way for synthesis of biodegradable antioxidant materials for the food industries.

2-Arylidene-1-indandiones as Pleiotropic Agents with Antioxidant and Inhibitory Enzymes Activities

Indandiones are a relatively new group of compounds presenting a wide range of biological activities. The synthesis of these compounds was performed via a Knoevenagel reaction between an aldehyde and 1,3-indandione and were obtained with a yield up to 54%. IR, 1H-Nucleic Magnetic Resonance (NMR), 13C-NMR, LC/MS ESI+ and elemental analysis were used for the confirmation of the structures of the novel derivatives. Lipophilicity values of compounds were calculated theoretically and experimentally by reversed chromatography method as values RM. The novel derivatives were studied through in vitro and in vivo experiments for their activity as anti-inflammatory and antioxidant agents and as inhibitors of lipoxygenase, trypsin, and thrombin. The inhibition of the carrageenin-induced paw edema (CPE) was also determined for representative structures. In the above series of experiments, we find that all the compounds showed moderate to satisfying interaction with the stable DPPH free radical in relation to the concentration and the time 2-arylidene-1-indandione (10) was the strongest. We observed moderate or very low antioxidant activities for selected compounds in the decolorization assay with ABTS+•. Most of the compounds showed high anti-lipid peroxidation of linoleic acid induced by AAPH.2-arylidene-1-indandione (7) showed a strongly inhibited soybean LOX. Only 2-arylidene-1-indandione (3) showed moderate scavenging activity of superoxide anion, whereas 2-arylidene-1-indandione (8) and 2-arylidene-1-indandione (9) showed very strong inhibition on proteolysis. 2-arylidene-1-indandione (8) highly inhibited serine protease thrombin. 2-arylidene-1-indandiones (7, 8 and 9) can be used as lead multifunctional molecules. The compounds were active for the inhibition of the CPE (30-57%) with 2-arylidene-1-indandione (1) being the most potent (57%). According to the predicted results a great number of the derivatives can cross the Blood-Brain Barrier (BBB), act in CNS and easily transported, diffused, and absorbed. Efforts are conducted a) to correlate quantitatively the in vitro/in vivo results with the most important physicochemical properties of the structural components of the molecules and b) to clarify the correlation of actions among them to propose a possible mechanism of action. Hydration energy as EHYDR and highest occupied molecular orbital (HOMO) better describe their antioxidant profile whereas the lipophilicity as RM values governs the in vivo anti-inflammatory activity. Docking studies are performed and showed that soybean LOX oxidation was prevented by blocking into the hydrophobic domain the substrates to the active site.

Multi-Target Cinnamic Acids for Oxidative Stress and Inflammation: Design, Synthesis, Biological Evaluation and Modeling Studies

Inflammation is a complex phenomenon that results as a healing response of organisms to different factors, exerting immune signaling, excessive free radical activity and tissue destruction. Lipoxygenases and their metabolites e.g., LTB₄, are associated with allergy, cell differentiation and carcinogenesis. Lipoxygenase 12/15 has been characterized as a mucosal-specific inhibitor of IgA and a contributor to the development of allergic sensitization and airway inflammation. Development of drugs that interfere with the formation or effects of these metabolites would be important for the treatment of various diseases like asthma, psoriasis, ulcerative colitis, rheumatoid arthritis, atherosclerosis, cancer and blood vessel disorders. In this study we extended our previous research synthesizing a series of multi-target cinnamic acids from the corresponding aldehydes with suitable 4-OH/Br substituted phenyl acetic acid by Knoevenagel condensation. The final products 1i, 3i, 3ii, 4i, 6i, 6ii, and 7i were obtained in high yields (52–98%) Their structures were verified spectrometrically, while their experimentally lipophilicity was determined as R_M values. The novel derivatives were evaluated for their antioxidant activity using DPPH, hydroxyl radical, superoxide anion and ABTS^+•, anti-lipid peroxidation and soybean lipoxygenase inhibition assays. The compounds presented medium interaction with DPPH (30–48% at 100 µM). In contrast all the synthesized derivatives strongly scavenge OH radicals (72–100% at 100 µM), ABTS^+• (24–83% at 100 µM) and presented remarkable inhibition (87–100% at 100 µM) in linoleic acid peroxidation (AAPH). The topological polar surface of the compounds seems to govern the superoxide anion scavenging activity. Molecular docking studies were carried out on cinnamic acid derivative 3i and found to be in accordance with experimental biological results. All acids presented interesting lipoxygenase inhibition (IC₅₀ = 7.4–100 µM) with compound 3i being the most potent LOX inhibitor with IC₅₀ = 7.4 µM combining antioxidant activities. The antioxidant results support the LOX inhibitory activities. The recorded in vitro results highlight compound 3i as a lead compound for the design of new potent lipoxygenase inhibitors for the treatment of asthma, psoriasis, ulcerative colitis, rheumatoid arthritis, atherosclerosis, cancer and blood vessel disorders.

A novel antioxidant: 6,6'-(butane-1,1-diyl)bis(4-methylbenzene-1,2-diol)

A novel compound, 6,6'-(butane-1,1-diyl)bis(4-methylbenzene-1,2-diol) (BMB), was synthesized through an acid-catalyzed condensation reaction between 4-methylcatechol (HPC) and butyraldehyde. When evaluated by the Rancimat and deep frying methods, BMB exhibited a stronger antioxidant activity than TBHQ. Its DPPH radical scavenging activity was also fairly higher than TBHQ, but lower compared to its mother phenol, HPC, due to its relative ease of binding DPPH•. BMB had the strongest scavenging ability of the 4-methylcatechol analogues reported to date. It could be used effectively to retard lipid peroxidation in both moderate and high temperature food preparations.

Butylated caffeic acid: An efficient novel antioxidant

A novel antioxidant, butylated caffeic acid (BCA) was rationally designed by adding a tert-butyl group to caffeic acid, which was synthesized at a high yield (36.2%) from 2-methoxy-4-methylphenol by a four-step reaction including Friedel-Crafts alkylation, bromine oxidation, ether bond hydrolysis and Knoevenagel condensation. Its antioxidant capacity was much stronger than common commercial antioxidant tert-butyl hydroquinone (TBHQ) and its mother compound, caffeic acid, in both rancimat and deep frying tests. When investigated via the DPPH method, the antioxidant capacity of BCA was almost equal to TBHQ, but lower than caffeic acid. BCA could be a potentially strong antioxidant, especially for food processing at high temperatures such as deep frying and baking.

Improving oxidative stability of virgin olive oil by addition of microalga Chlorella vulgaris biomass

Antioxidant activity of Chlorella (Chlorella vulgaris) was evaluated in virgin olive oil (VOO) at different concentrations of 0.5, 1.0, and 1.5% (w/w) under accelerated storage conditions. Antioxidant activity of Chlorella was compared with those of BHT and β-carotene. Chlorella samples significantly retarded the formation of primary, secondary, and total oxidation products in comparison with those of the control. The stability increased as concentrations of Chlorella increased. Samples containing 0.5, 1.0, and 1.5% Chlorella significantly improved VOO stability by 19.99, 28.83, and 33.14%, respectively. Observed effects can be related to the release in the assortment of bioactive compounds from Chlorella algae to the VOO. Among the different antioxidants evaluatedy, BHT exhibited the highest antioxidant activity. On the contrary, β-carotene had no preventive effect against the oxidation of VOO. It also proved incapable of limiting the progress of VOO oxidation and played role as pro-oxidant. In conclusion, Chlorella enhanced VOO oxidative stability. Thus it can be considered as a promising source of natural antioxidants.

Effects of High Temperature Frying of Spinach Leaves in Sunflower Oil on Carotenoids, Chlorophylls, and Tocopherol Composition

Spinach is one of the highly consumed vegetable, with significant nutritional, and beneficial properties. This study revealed for the first time, the effects of high temperature frying on the carotenoids, chlorophylls, and tocopherol contents of spinach leaves. Spinach leaves were thermally processed in the sunflower oil for 15, 30, 45, and 60 min at 250°C. Reversed phase HPLC-DAD results revealed a total of eight carotenoids, four chlorophylls and α-tocopherol in the spinach leaves. Lutein, neoxanthin, violaxanthin, and β-carotene-5,6-epoxide were the major carotenoids, while chlorophyll a and b' were present in higher amounts. Frying of spinach leaves increased significantly the amount of α-tocopherol, β-carotene-5,6-epoxide, luteoxanthin, lutein, and its Z-isomers and chlorophyll b' isomer. There was significant decrease in the amounts of neoxanthin, violaxanthin, chlorophyll b, b' and chlorophyll a with increase of frying time. The increase of frying time increased the total phenolic contents in spinach leaves and fried sunflower oil samples. Chemical characteristics such as peroxide values, free fatty acids, conjugated dienes, conjugated trienes, and radical scavenging activity were significantly affected by frying, while spinach leaves increased the stability of the frying oil. This study can be used to improve the quality of fried vegetable leaves or their products at high temperature frying in food industries for increasing consumer acceptability.

The supramolecular chemistry of lipid oxidation and antioxidation in bulk oils

The microenvironment formed by surface active compounds is being recognized as the active site of lipid oxidation. Trace amounts of water occupy the core of micro micelles and several amphiphilic minor components (e.g., phospholipids, monoacylglycerols, free fatty acids, etc.) act as surfactants and affect lipid oxidation in a complex fashion dependent on the structure and stability of the microemulsions in a continuous lipid phase such as bulk oil. The structures of the triacylglycerols and other lipid-soluble molecules affect their organization and play important roles during the course of the oxidation reactions. Antioxidant head groups, variably located near the water-oil colloidal interfaces, trap and scavenge radicals according to their location and concentration. According to this scenario, antioxidants inhibit lipid oxidation not only by scavenging radicals via hydrogen donation but also by physically stabilizing the micelles at the microenvironments of the reaction sites. There is a cut-off effect (optimum value) governing the inhibitory effects of antioxidants depending inter alias on their hydrophilic/lipophilic balance and their concentrations. These complex effects, previously considered as paradoxes in antioxidants research, are now better explained by the supramolecular chemistry of lipid oxidation and antioxidants, which is discussed in this review.

Biosynthesis, natural sources, dietary intake, pharmacokinetic properties, and biological activities of hydroxycinnamic acids

Hydroxycinnamic acids are the most widely distributed phenolic acids in plants. Broadly speaking, they can be defined as compounds derived from cinnamic acid. They are present at high concentrations in many food products, including fruits, vegetables, tea, cocoa, and wine. A diet rich in hydroxycinnamic acids is thought to be associated with beneficial health effects such as a reduced risk of cardiovascular disease. The impact of hydroxycinnamic acids on health depends on their intake and pharmacokinetic properties. This review discusses their chemistry, biosynthesis, natural sources, dietary intake, and pharmacokinetic properties.

Phenolic compounds from Andean mashua (Tropaeolum tuberosum) tubers display protection against soybean oil oxidation

Phenolic compounds from mashua tuber were evaluated as potential antioxidants to retard the oxidation of crude soybean oil submitted to accelerated storage and frying. During the accelerated storage, an ethanolic crude extract, a purified extract, an aqueous fraction and an ethyl acetate fraction from mashua containing different gallic acid equivalent concentrations (100, 300 and 600 ppm) in oil were evaluated at 55 °C. After 15 days of storage, better effects were evidenced against soybean oil oxidation at 300 and 600 ppm of ethyl acetate fraction in comparison to 200 ppm butylated hydroxytoluene and the control (no antioxidant added). During the frying process at ∼180 °C, principal component analysis revealed that the content of trienes and dienes were strongly correlated with the frying batch. Ethyl acetate fraction at 200 ppm showed the highest efficacy against oil oxidation in terms of polar compound values, free fatty acids and conjugated dienes and trienes in comparison to the oil containing 200 ppm tert-butylhydroquinone and control. Differential scanning calorimetry corroborated the efficacy of ethyl acetate fraction phenolic and it is strongly recommended as method for validation of results. This study provides strong evidence related to the excellent protective effects against soybean oil oxidation of mashua phenolics. This crop could be utilized as an alternative source of natural antioxidants by the oil industry.

Antioxidants modulate molecular mobility, oxygen permeability, and microstructure in zein films

The effect of octyl gallate and propyl gallate on the molecular mobility, oxygen permeability, and microstructure of zein/glycerol films was studied. Films were cast from 70% ethanol/water containing 20% (w/w) glycerol and different amounts of the antioxidants propyl gallate or octyl gallate. The oxygen permeability and local mobility of these films were measured using phosphorescence from the dispersed triplet probe erythrosin B. Although both antioxidants increased the local mobility of the zein matrix to about the same extent, octyl gallate and to a lesser extent propyl gallate dramatically increased the permeability of the film to oxygen. Atomic force microscopy imaging indicated that propyl gallate induced aggregation of zein complexes, which could lead to a more condensed film. These results indicate that the addition of specific functional ingredients, such as antioxidants, to edible films may significantly affect the physical properties and structure and, thus, functional properties in ways that influence their eventual use.

Natural and synthetic antioxidant additives for improving the performance of new biolubricant formulations

Knowledge of the oxidative stability of vegetable oils for lubricant applications is a key point, because vegetable oil oxidation potential is the main disadvantage for its use as a lubricant. Oil degradation after an oxidation process can seriously affect its lubricating function and increase wear. In this work, two different methods for evaluating the oxidation stability of lubricating vegetable oils, the oxidation onset temperature, characterized through DSC measurements (ASTM E 2009-08), and the pressure drop in the oxygen pressure vessel (ASTM D 942-02), have been used. Additionally, thermogravimetric analysis and FTIR studies have also been carried out. High-oleic sunflower (HOSO) and castor (CO) oils were selected and blended with natural ((+)-α-tocopherol (TCP), propyl gallate (PG), l-ascorbic acid 6-palmitate (AP)) or synthetic antioxidants (4,4'-methylenebis(2,6-di-tert-butylphenol) (MBP)), with the aim of formulating biodegradable vegetable-based lubricants according to REACH regulation. (1) The results showed that the most effective biodegradable antioxidant is PG, comparable to MBP, whereas lower effectiveness was obtained for TCP and AP. In relation to the methods tested, DSC measurements achieve accurate data more quickly for evaluating the oxidation stability of these basestocks, showing a linear correlation with the traditional method based on the oxygen bomb test. The empirical equation obtained depends on the mechanism involved in the antioxidant activity.

Alkyl esters of hydroxycinnamic acids with improved antioxidant activity and lipophilicity protect PC12 cells against oxidative stress

Hydroxycinnamic acids (HCAs) are phenolic compounds present in dietary plants, which possess considerable antioxidant activity. In order to increase the lipophilicity of HCAs, with the aim of improving their cellular absorption and expansion of their use in lipophilic media, methyl, ethyl, propyl and butyl esters of caffeic acid and ferulic acid have been synthesized. All caffeate esters had a slightly lower DPPH IC(50) (13.5-14.5 μM) and higher ferric reducing antioxidant power (FRAP) values (1490-1588 mM quercetin/mole [mMQ/mole]) compared to caffeic acid (16.6 μM and 1398 mMQ/mole, respectively) in antioxidant assays. In contrast, ferulate esters were less active in DPPH (56.3-74.7 μM) and FRAP assays (193-262 mMQ/mole) compared to ferulic acid (44.6 μM and 324 mMQ/mole, respectively). Redox properties of HCAs were in line with their antioxidant capacities, so that compounds with higher antioxidant activities had lower oxidation potentials. Measurement of partition coefficients disclosed the higher lipophilicity of the esters compared to parent compounds. All esters of caffeic acid significantly inhibited hydrogen peroxide-induced neuronal PC12 cell death assessed by MTT assay at 5 and 25 μM. However, caffeic acid, ferulic acid and ferulate esters were not able to protect the cells. In conclusion, these findings suggest that alkyl esterification of some HCAs augments their antioxidant properties as well as their lipophilicity and as a consequence, improves their cell protective activity against oxidative stress. These compounds could have useful applications in conditions where oxidative stress plays a pathogenic role.

Stabilization of sunflower oil with Carum copticum Benth & Hook essential oil

In this study, application of various concentrations (0.025%, 0.05% and 0.075%) of Carum copticum essential oil (EO) were examined on oxidative stability of sunflower oil and there were compared to Butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) during storage at 37 and 47 °C. The main compounds of EO were identified as thymol (50.07%), γ- terpinene (23.92%) and p-cymene (22.9%). Peroxide value (PV), anisidine value (AnV) and thiobarbituric acid (TBA) value measurement in sunflower oil showed that all concentrations of EO had antioxidant effect in comparison to BHA and BHT. Samples added with EO at 0.075% were the most stable during storage at both temperatures (P < 0.05). Furthermore, Totox value, antioxidant activity (AA), stabilization factor (F) and antioxidant power (AOP) determination confirmed efficacy of this EO as antioxidant in sunflower oil. EO also was able to reduce the stable free radical 2, 2-diphenyl-1-picrylhydrazyl (DPPH) with a 50% inhibition concentration (IC50) of 20.3 ± 0.9 μg/mL. Therefore, the results indicate that EO could be used as a natural antioxidant in food lipids.

Anti-dermatitis effects of oak wood vinegar on the DNCB-induced contact hypersensitivity via STAT3 suppression

AIMS OF THE STUDY

The aim of this study was to evaluate the anti-dermatitis effects of oak wood vinegar (OWV) in a 2,4-dinitrochlorobenzene (DNCB)-induced contact dermatitis mice model.

MATERIALS AND METHODS

Immunoglobulin E (IgE) production, infiltration of immune cells (neutrophils, CD3+ cells), inducible nitric oxide synthase (iNOS) expression, skin thickness, and expression of phosphorylated STAT3 (signal transducers and activators of transcription 3) protein were tested in a DNCB-induced contact dermatitis model. In vitro wound healing and proliferative assays were also performed.

RESULTS

OWV showed anti-inflammatory effects on DNCB-induced dermatitis in mice, leading to inhibition of IgE production, immune cell infiltration, and iNOS expression. Skin thickness and the level of phospho-STAT3 were dramatically reduced by OWV. Using the HaCaT human keratinocyte cell line, we confirmed that constitutive STAT3 activation induced faster proliferation of epithelial cells. In addition, OWV suppressed HaCaT proliferative ability and phospho-STAT3 levels.

CONCLUSIONS

The study revealed that OWV has anti-inflammatory and anti-proliferative effects in a DNCB-induced contact dermatitis mice model. Furthermore, we showed that the mechanism by which OWV most likely inhibits epithelial proliferation is through STAT3 inactivation.

Theoretical and experimental vibrational spectrum study of 4-hydroxybenzoic acid as monomer and dimer

Theoretical calculations on the molecular geometry and the vibrational spectrum of 4-hydroxybenzoic acid were carried out by the Density Functional Theory (DFT/B3LYP) method. In addition, IR and Raman spectra of the 4-hydroxybenzoic acid in solid phase were newly recorded using them in conjunction the experimental and theoretical data (including SQM calculations), a vibrational analysis of this molecular specie was accomplished and a reassignment of the normal modes corresponding to some spectral bands was proposed. The geometries of monomers and dimers in gas phase were optimized using the DFT B3LYP method with the 6-31G*, D95** and 6-311++G** basis sets. Also, both the vibrational spectra recorded and the results of the theoretical calculations show the presence of one stable conformer for the 4-hydroxybenzoic acid cyclic dimer. The B3LYP/6-31G* method was used to study the structure for cyclic dimer of 4-hydroxybenzoic acid and for a complete assignment our results were compared with results of the cyclic dimer of benzoic acid. A scaled quantum mechanical analysis was carried out to yield the best set of harmonic force constants. The formation of the hydrogen bond was investigated in terms of the charge density by the AIM program and by the NBO calculations.

Radical scavenging activity of lipophilized products from lipase-catalyzed transesterification of triolein with cinnamic and ferulic acids

Lipase-catalyzed transesterification of triolein with cinnamic and ferulic acids using an immobilized lipase from Candida antarctica (E.C. 3.1.1.3) was conducted to evaluate the antioxidant activity of the lipophilized products as model systems for enhanced protection of unsaturated oil. The lipophilized products were identified using ESI-MS. Free radical scavenging activity was determined using the DPPH radical method. The polarity of the solvents proved important in determining the radical scavenging activity of the substrates. Ferulic acid showed much higher radical scavenging activity than cinnamic acid, which has limited activity. The esterification of cinnamic acid and ferulic acid with triolein resulted in significant increase and decrease in the radical scavenging activity, respectively. These opposite effects were due to the effect of addition of electron-donating alkyl groups on the predominant mechanism of reaction (hydrogen atom transfer or electron transfer) of a species with DPPH. The effect of esterification of cinnamic acid was confirmed using ethyl cinnamate which greatly enhances the radical scavenging activity. Although, compared to the lipophilized cinnamic acid product, the activity was lower. The radical scavenging activity of the main component isolated from lipophilized cinnamic acid product using solid phase extraction, monocinnamoyl dioleoyl glycerol, was as good as the unseparated mixture of lipophilized product. Based on the ratio of a substrate to DPPH concentration, lipophilized ferulic acid was a much more efficient radical scavenger than lipophilized cinnamic acid.

Antioxidant activity of a combinatorial library of emulsifier-antioxidant bioconjugates

A combinatorial chemistry approach was employed for the design and systematic synthesis of antioxidant-emulsifier bioconjugates to improve antioxidant activity in the interface between oil and water. A combinatorial library of 12 bioconjugates was synthesized from the phenolic antioxidants Trolox (a water-soluble alpha-tocopherol analogue), dihydroferulic acid, dihydrocaffeic acid, and gallic acid in combination with serine ethyl ester, serine lauryl ester, and lauroyl serine by esterification of the serine side chain or amidation, respectively. The bioconjugates were characterized by NMR and mass spectrometry, and each was tested for antioxidant activity by measuring the radical scavenging rate of 2,2-diphenyl-1-picrylhydrazyl (DPPH (*)) in methanol, the radical scavenging rate of DPPH (*) in a heterogeneous solvent system, the rate of oxygen consumption in an oil-in-water emulsion with metmyoglobin initiated oxidation, and the lag phase for diene formation in unilamellar liposomes with free radical initiation in the aqueous phase; each case was compared to the antioxidant activity of the parent antioxidant. In general, the conjugates with longer chain derivatives exhibited improved antioxidative activity in heterogeneous systems, whereas no improvement was observed in homogeneous solution. The rate of oxygen consumption in oil-in-water emulsion was found to decrease with increasing octanol/water partition coefficient, which is suggested to correspond to a saturation of the water/oil interface with antioxidant bioconjugate to approach maximal protection.

Structure-activity relationship of C6-C3 phenylpropanoids on xanthine oxidase-inhibiting and free radical-scavenging activities

We employed the techniques of DNA relaxation, DPPH (1,1-diphenyl-2-picrylhydrazyl hydrate), and DMPO (5,5-dimethyl-1-pyrroline-N-oxide)-electron spin resonance (ESR), to study the effects of reactive oxygen species (ROS) suppression by 11 selected C6-C3 phenylpropanoid derivatives under oxidative conditions. We also investigated the effects of the derivatives on the inhibition of xanthine oxidase (XO) activity, and the structure-activity relationships (SARs) of these derivatives against XO activity were further examined using computer-aided molecular modeling. Caffeic acid was the most potent radical scavenger among the 11 test compounds. Our results suggest that the chemical structure and number of hydroxyl groups on the benzene ring of phenylpropanoids are correlated with the effects of ROS suppression. All test derivatives were competitive inhibitors of XO. The results of the structure-based molecular modeling exhibited interactions between phenylpropanoid derivatives and the molybdopterin region of XO. The para-hydroxyl of phenylpropanoid derivatives was pointed toward the guanidinium group of Arg 880. The phenylpropanoid derivatives containing the meta-or ortho-hydroxyl formed hydrogen bonds with Thr 1010. In addition, meta-hydroxyl formed hydrogen bonds with the peptide bond between the residues of Thr1010 and Phe1009. CAPE, the phenylenethyl ester of phenylpropanoids, had the highest affinity toward the binding site of XO, and we speculated that this was due to hydrophobic interactions of the phenylethyl ester with several hydrophobic residues surrounding the active site. The hypoxanthine/XO reaction in the DMPO-ESR technique was used to correlate the effects of these phenylpropanoid derivatives on enzyme inhibition and ROS suppression, and the results showed that caffeic acid and CAPE were the two most potent agents among the tested compounds. We further assessed the effects of the test compounds on living cells, and CAPE was the most potent agent for protecting cells against ROS-mediated damage among the tested phenylpropanoids.

Environmental effects on the spectroscopic properties of gallic acid: a combined classical and quantum mechanical study

The solvation of gallic acid (in water and acetonitrile) is studied by means of its spectroscopic properties. IR, UV, and NMR spectra are predicted by using various solvation models obtained in terms of both purely classical and density functional approaches. Comparison with experiments is used to validate solvation models. Hydrogen-bond and long-range (or bulk) effects are evaluated by comparing different solvation models. A continuum-only approach, a purely discrete, and a mixed continuum/discrete approach based on quantum-mechanical and classical molecular-dynamics solute-solvent clusters are tested.

Caffeic acid and its synthetic derivative CADPE suppress tumor angiogenesis by blocking STAT3-mediated VEGF expression in human renal carcinoma cells

Tumor angiogenesis is required for tumor development and is stimulated by angiogenic inducers like VEGF (vascular endothelial growth factor). Our previous study demonstrated that STAT3 (signal transducer and activator of transcription 3) up-regulates HIF-1alpha (hypoxia inducible factor-1alpha) protein stability and enhances HIF-1-mediated VEGF expression in hypoxic solid tumor cells, thus suggesting that the inhibition of STAT3 signaling may have clinical applications. In this study, we examined in vitro and in vivo, whether caffeic acid (CA) or its derivative CADPE [3-(3,4-dihydroxy-phenyl)-acrylic acid 2-(3,4-dihydroxy-phenyl)-ethyl ester] exert anticancer activity by targeting STAT3. It was found that CA or CADPE significantly inhibit STAT3 activity, and that this in turn down-regulates HIF-1alpha activity. Consequently, sequential blockade of STAT3 and HIF-1alpha resulted in the down-regulation of VEGF by inhibiting their recruitment to the VEGF promoter. In mice bearing a Caki-I carcinoma, both CA and CADPE retarded tumor growth and suppressed STAT3 phosphorylation, HIF-1alpha expression, vascularization and STAT3-inducible VEGF gene expression in tumors. Taken together, our results demonstrate that CA and CADPE are potential inhibitors of STAT3 and that they suppress tumor angiogenesis by inhibiting the activity of STAT3, the expression of HIF-1alpha and VEGF.

Antioxidant profile of dihydroxy- and trihydroxyphenolic acids--a structure-activity relationship study

Eight structurally similar dihydroxy and trihydroxyphenolic acids (protocatechuic acid, 3,4-dihydroxyphenylacetic acid, hydrocaffeic acid, caffeic acid, gallic acid, 3,4,5-trihydroxyphenylacetic acid, 3-(3,4,5-trihydroxyphenyl)propanoic acid and 3-(3,4,5-trihydroxyphenyl)propenoic acid) were examined for their total antioxidant capacity (TAC). Furthermore, their ability to scavenge peroxyl radicals, generated by AAPH in liposomes, was determined. The antioxidant/pro-oxidant activity of the compounds was screened using the 2'-deoxyguanosine assay. All compounds behave as radical scavengers, with 3,4,5-trihydroxyphenylacetic acid being the most potent. Nevertheless, in the lipid peroxidation assay an inverse ranking order was observed, 3,4-dihydroxyphenylacetic acid being the most effective compound. All the dihydroxylated compounds showed a pro-oxidant behaviour leading to an increase of 50% in 8-OH-dG induction. From the structure-antioxidant activity relationship studies performed it may be concluded that the number of phenolic groups and the type of the alkyl spacer between the carboxylic acid and the aromatic ring strongly influence the antioxidant activity.