Phloroglucinol Carboxylic Acid Research Articles

The degradation and antioxidant capacity of anthocyanins from eggplant peels in the context of complex food system under thermal processing

A model of complex food system composed of dietary fiber, protein, starch (3/2/2), added with anthocyanins extracted from purple eggplant peels was constructed to investigate impacts of thermal treatments (including steaming, boiling, microwave and frying) on the degradation and antioxidant capacity of anthocyanins. The content of anthocyanins was reduced by 84.48% under frying treatment (185 ± 5 °C), and the degradation of anthocyanins was in line with second-order kinetics as with microwave treatment (700 W). Under boiling and steaming conditions, the degradation of anthocyanins followed first-order kinetics. Additionally, the antioxidant capacity was positively correlated with the contents of total anthocyanins and polyphenols. During thermal treatments, anthocyanins were mainly decomposed into gallic acid, phloroglucinaldehyde, and 2,4-dihydroxybenzoic acid (frying), in which phloroglucinaldehyde could be further isomerized into phloroglucinic acid. The results of scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) also supported that frying showed the most robust effect on influencing the structure of anthocyanins during these four thermal treatments.

Empirical Kinetic Modelling and Mechanisms of Quercetin Thermal Degradation in Aqueous Model Systems: Effect of pH and Addition of Antioxidants

Quercetin (Qt) is a natural flavonoid of high biological significance, and it occurs in a wide variety of plant foods. Although its oxidation by various means has been extensively studied, its behavior with regard to thermal treatments remains a challenge. The study described herein aimed at investigating Qt thermal decomposition, by proposing an empirical sigmoidal model for tracing degradation kinetics. This model was employed to examine the effect of addition of antioxidants on Qt thermal degradation, including ascorbic acid, L-cysteine, and sulfite. Furthermore, degradation pathways were proposed by performing liquid chromatography-tandem mass spectrometry analyses. Upon addition of any antioxidant used, the sigmoidal course of Qt thermal degradation was pronounced, evidencing the validity of the empirical model used in the study of similar cases. The antioxidants retarded Qt degradation in a manner that appeared to depend on Qt/antioxidant molar ratio. No major differentiation in the degradation mechanism was observed in response to the addition of various antioxidants, and in all cases protocatechuic acid and phloroglucinol carboxylic acid were typical degradation products identified. Furthermore, in all cases tested the solutions resulted after thermal treatment possessed inferior antioxidant properties compared to the initial Qt solutions, and this demonstrated the detrimental effects of heating on Qt. The empirical model proposed could be of assistance in interpreting the degradation behavior of other polyphenols, but its validity merits further investigation.

Removing organic harmful compounds from the polluted water by a novel synthesized cobalt(II) and titanium(IV) containing photocatalyst under visible light

A facile approach for the synthesis of nanoporous cobalt oxide, anatase, rutile, and mix of rutile-anatase phase through thermal decomposition of organometallic complex compounds of phloroglucinol carboxylic acid were used for the first time in order to remove the organic-harmful compounds from water. The complex compounds and nanoparticles were characterized by X-ray diffraction (XRD), UV–vis spectroscopy, FT-IR spectroscopy, elemental analysis (metal, organic atoms), Field-Emission Scanning Electron microscopy (SEM), NMR spectroscopy, quantum chemical modeling, photoluminescence, and thermal analysis techniques. The results illustrated that TiO2 nanoparticles in three different structures/ phases (Anatase, Anatase-Rutile mixture, and Rutile) and nanoporous cobalt oxide were isolated.In order to examine the possibility of modification of the structures based on TiO2, a new method was also applied, including grinding and thermal decomposition of titanium and cobalt complexes in the different ratio (10 %-to-90 %). Titanium and cobalt complexes were mixed, and ground well and then heated to 500 °C for 2 h. Nanoparticles of titanium and cobalt oxides mixtures were studied by SEM, EDX, XRD, and photoluminescence methods. The ability of the obtained product in the environmental field was tested. The results showed it led to the formation of cobalt (II) titanate of perovskite-like structures and Ti80 %Co20 % ratio was the most proper ratio to absorb visible light. Finally, this sample was used as a photocatalyst to degrade bromophenol blue (BPB), as a harmful organic target, under visible light and it could reduce the concentration of BPB to 82 % after 120 min, which showed it to be a powerful photocatalyst to treat water.

Modification of quercetin with l-cysteine by horseradish peroxidase

Horseradish peroxidase is a well-known member of the peroxidase family that catalyzes oxidation of flavonoids and phenolic substrates to free phenoxyl or semiquinone radicals. Aim of this study was to investigate in vitro oxidation of quercetin by horseradish peroxidase in the presence of l-cysteine as nucleophilic agent, and its influence on previously formed semiquinone- and quinone-type metabolites. The obtained results showed that in the reaction without l-cysteine several products were present, such as quercetin quinone methide, phloroglucinol carboxylic acid, protocatechuic acid, as well as quercetin heterodimer and derivates of quercetin heterodimer. On the other hand, in the presence of l-cysteine only three products were obtained, quercetin quinone methide and two new isomeric mono-cysteine derivatives of quercetin with mass exp. m/z 420.04 ± 0.1 [quercetin + cysteine–H]– (theor. m/z 420.0389 [quercetin + cysteine–H]–).

Distribution of Polyphenol Oxidase in some Cruciferae Vegetables

Enzymatic oxidation of polyphenolic compounds in damaged tissue of many fruits and vegetables induced undesirable browning as results in decreased marketability of products. A new type of polyphenol oxidase (PPO) that is “Phloroglucinol Oxidase (PhO)” have been reported in turnip and cabbage, and the purified enzymes also had strong peroxidase (POD) activity. Distribution of PPO from different plant source of cruciferae vegetables were observed. Cabbage, broccoli, turnip and cauliflower PPOs from Indonesia and Japan strongly oxidized 1,3,5-trihydroxybenzenes such as phloroglucinol (Phl) and phloroglucinol carboxylic acid, but not oxidized 1,2,3-trihydroxybenzenes and o-diphenol. On the other side, Chinese mustard, Chinese cabbage, shingensai, Japanese radish root, mizuna, takana, leaf mustard, katsuona and komatsuna also strongly oxidized 1,3,5-trihydroxybenzenes and little oxidized 1,2,3-trihydroxybenzenes such as pyrogallol and gallic acid, but not oxidized o-diphenol. These results indicated that the PPOs in all cruciferae vegetables are a group of a new type of PPO, however, the level activity of 7 varieties of vegetables from Indonesia and 15 varieties from Japan tested showed different activity level of PhO and POD.

Lysilactones A–C, three 6H-dibenzo[b,d]pyran-6-one glycosides from Lysimachia clethroides, total synthesis of Lysilactone A

Three 6H-dibenzo[b,d]pyran-6-one glycosides named lysilactones A–C (1–3) were isolated from the aerial parts of Lysimachia clethroides. Their structures were elucidated using spectroscopic analysis and chemical evidence. This is the first report of 6H-dibenzo[b,d]pyran-6-one glycosides. Furthermore, we have finished a total synthesis of lysilactone A. The key step is a Suzuki coupling used for the construction of the central biaryl bond. Lysilactone A was prepared in eight steps starting from phloroglucinic acid and orcinol, where the longest linear sequence is seven steps.

Revision of the Structure and Total Synthesis of Altenuisol

AbstractA total synthesis of the reported structure of altenuisol is described. Comparison of the 1H NMR spectra of the synthesized compound and of the natural product revealed that the originally proposed structure was not correct. Consequently, two constitutional isomers were synthesized. The spectra of one of these compounds – a structure originally proposed as the structure of altertenuol – matched perfectly with the spectra of the natural product. The total synthesis of altenuisol was thus achieved starting with phloroglucinic acid and protocatechuic aldehyde in 10 steps and in 23 % yield, where the longest linear sequence consisted of 6 steps. The key step was a Suzuki coupling with concomitant formation of the lactone ring. Whether altertenuol is identical with altenuisol could not be decided.

Purification and Characterization of Polyphenol Oxidase from Cauliflower (Brassica oleracea L.)

Polyphenol oxidase (PPO) of cauliflower was purified to 282-fold with a recovery rate of 8.1%, using phloroglucinol as a substrate. The enzyme appeared as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The estimated molecular weight of the enzyme was 60 and 54 kDa by SDS-PAGE and gel filtration, respectively. The purified enzyme, called phloroglucinol oxidase (PhO), oxidized phloroglucinol (K(m) = 3.3 mM) and phloroglucinolcarboxylic acid. The enzyme also had peroxidase (POD) activity. At the final step, the activity of purified cauliflower POD was 110-fold with a recovery rate of 3.2%. The PhO and POD showed the highest activity at pH 8.0 and 4.0 and were stable in the pH range of 3.0-11.0 and 5.0-8.0 at 5 °C for 20 h, respectively. The optimum temperature was 55 °C for PhO and 20 °C for POD. The most effective inhibitor for PhO was sodium diethyldithiocarbamate at 10 mM (IC(50) = 0.64 and K(i) = 0.15 mM), and the most effective inhibitor for POD was potassium cyanide at 1.0 mM (IC(50) = 0.03 and K(i) = 29 μM).

Total Synthesis of Altenusin and Alterlactone

The resorcylic lactone alterlactone, a mycotoxin produced by alternaria sp., was synthesized for the first time. The total synthesis was achieved in nine steps with 69% yield starting with acetal-protected phloroglucinic acid and 6-bromopiperonal, where the longest linear sequence consists of five steps. Key step is a ­Suzuki coupling used for the construction of the central biaryl bond. When the final deprotection with cleavage of benzyl ethers (yielding unprotected alterlactone) was performed in a less polar solvent the biaryl mycotoxin altenusin was obtained.

ChemInform Abstract: Total Synthesis of Graphislactone G.

AbstractThe synthesis of title compound (V), a constituent of the endophytic fungus Cephalosporium acremonium (IFB‐E007), is completed in 13 steps and 22% yield starting from orcinol (I) and phloroglucinic acid.

Total synthesis of graphislactone G

Abstract We present a total synthesis of the fungal natural product graphislactone G, a chlorinated resorcylic lactone. The key step is a Suzuki coupling used for the construction of the central biaryl bond. Graphislactone G was prepared in 13 steps with 22% yield starting with orcinol and phloroglucinic acid, where the longest linear sequence consists of nine steps.

Enhanced Catalytic Activity of Gold Nanoparticles Doped in a Mesoporous Organic Gel Based on Polymeric Phloroglucinol Carboxylic Acid−Formaldehyde

Gold nanoparticles were supported by a phloroglucinolcarboxylic acid-formaldehyde (PF) gel, a new organic gel with a 30 nm spheroid-like structure. The surface area of the PF gel with gold nanoparticles was 550 m(2)/g. Gold nanoparticles supported on a PF gel exhibited catalytic activity in the reduction of 4-nitrophenol with a reaction rate constant of 7.4 x 10(-3) s(-1), which is high in the reported heterogeneous reaction system. The adsorption behavior of 4-nitrophenol into the gel support was observed by ultraviolet-visible absorption spectroscopy. Gold nanoparticles in the PF network were characterized by scanning electron microscopy, atomic force microscopy, and transmission electron microscopy observation. The high reduction rate would be attributed to the extraction and diffusion of the reactant through the pores of a PF gel support to encounter the highly dispersed gold nanoparticles on the surface and inside the material.

Total Synthesis of Neoaltenuene

AbstractThe total synthesis of neoaltenuene, a toxin produced by alternaria fungi, has been achieved for the first time in 14 steps in a yield of 10 % starting from quinic acid and phloroglucinic acid, the longest linear sequence consisting of 10 steps. The key reaction was a palladium‐catalyzed Suzuki‐type coupling of an arene boronate with an iodinated cyclohexene.4a‐epi‐Neoaltenuene, a non‐natural isomer has been synthesized similarly. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Thin shell aerogel fabrication for FIREX-I targets using high viscosity (phloroglucinol carboxylic acid)/formaldehyde solution

AbstractCapsules with a thin aerogel shell were prepared by the OO/W/OIemulsion process. (Phloroglucinol carboxylic acid)/formaldehyde (PF) was used as the water phase (W) solution to form the shell of the capsule. PF is a linear polymer prepared from phloroglucinol carboxylic acid. The viscosity of the PF solution can reach a high level of 9×10−5m2/s without gelation while resorcinol/formaldehyde (RF) gelates at ~3–4×10−5m2/s. Using the viscous PF solution, capsule with a 17 µm gel shell was fabricated. This thickness satisfies the specification of the first phase of Fast Ignition Realization Experiment (FIREX-I) at Osaka University. When PF gel was extracted to remove the organic solvent, shrinkage of 9% occurred. The final density of the PF aerogel was 145 mg/cm3. Both the shell thickness and density can satisfy the specification of FIREX-I. The pore size of the PF aerogel was less than 100 nm while that of RF was 200–500 nm. The SEM showed that PF had particle-like foam structure while RF had fibrous-like foam structure.

Solution viscosity adjustable phloroglucinolcarboxylic acid/formaldehyde applied in extremely thin shell fusion target fabrication

Capsuliform fusion target was prepared by using the OO/W/OI emulsion process. Phloroglucinolcarboxylic acid / formaldehyde (PF) is expected to be used as the water phase (W) solution which then gelates to be the shell of the capsule. The density of the shell should be low to obtain high laser gain. Phloroglucinolcarboxylic acid had addition and condensation reaction with formaldehyde under basic condition to form linear polymer first. The nano-scale linear polymers were then linked via noncovalent interactions, such as hydrogen bonding, van der Waals, to continue the gelation process. The type and amount of the base catalyst used in the reaction can affect the polymerization of PF, including the gelation rate and gelation concentration. By changing the basic condition of the reaction, the proper viscosity of 9×10−5 for capsuliform target fabrication was reached and extremely thin gel shell thickness of 17μm with low polymer concentration of 26.3mg/cm3 was obtained.

Investigation on biocatalytic properties of a peroxidase-active homogenate from onion solid wastes: An insight into quercetin oxidation mechanism

Enzyme-assisted bioremediation studies have been based to a large extent on the use of microbes (bacteria or fungi). On the other hand, plants and/or plant food wastes have been given much less attention or even disregarded. In some instances, however, oxidative enzymes from residual plant tissues have been shown to effectively degrade recalcitrant pollutants. In this regard, this study deals with the examination of some biocatalytic properties of a peroxidase-active homogenate, obtained from onion solid wastes. The examinations were carried out using the flavonol quercetin (3,3′,4′,5,7-pentahydroxyflavone), which is the physiological substrate of the enzyme. Quercetin oxidation by the homogenate/H 2O 2 system was shown to be optimum at pH values between 3 and 4 and temperature between 30 and 40 °C. Liquid chromatography–mass spectrometry analyses of a homogenate/H 2O 2-oxidised quercetin solution revealed the formation of four major products, including 3,4-dihydroxybenzoic acid (protocatechuic acid), 2,4,6-trihydroxybenzoic acid (phloroglucinol carboxylic acid), 2-(2-((3,4-dioxocyclohexa-1,5-dienyl)(hydroxyl)methoxy)-4,6-dihydroxyphenyl)-2-oxoacetic acid, and 2-(3,4-dihydroxybenzyloxy)-4,6-dihydroxybenzoic acid. Minor amounts of a quercetin heterodimer were also detected. The tentative identification of these substances permitted an approach to an unusual, putative oxidation pathway for quercetin, catalysed by onion peroxidase.

Total Synthesis of Altenuene and Isoaltenuene

AbstractTotal synthesis of altenuene and isoaltenuene, toxins produced by various alternaria fungi, were achieved for the first time in ten steps, starting with quinic acid and commercially available acetal‐protected phloroglucinic acid, with the longest linear sequence consisting of seven steps. The key reactions are palladium‐catalyzed Suzuki‐type couplings between an arene boronate and iodinated cyclohexenes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

First Chemical Synthesis of Three Natural Depsides Involved in Flavonol Catabolism and Related to Quercetinase Catalysis

We report here the first chemical synthesis of three depsides related to quercetinase‐catalyzed degradation of kaempferol, quercetin, and myricetin. The three depsides were constructed through the coupling of suitably protected phloroglucinol carboxylic acid and hydroxy‐perbenzylated, derivatives of gallic, protocatechuic, and 4‐hydroxy benzoic acids. The three synthesized target compounds proved to be identical to their natural counterparts, arising from quercetinase action on corresponding flavonols.

Evaluation of phenolics and sugars as inducers of quercetinase activity in Penicillium olsonii

Quercetinase is produced by various filamentous fungi when grown on rutin as sole carbon and energy source. We investigated on the effect of 10 phenolics and two sugars, structurally related to substrates and products of the rutin catabolic pathway, on the induction of a quercetinase activity in Penicillium olsonii. Neither the sugars (glucose and rhamnose, two constituents of rutin), nor phenolics such as protocatechuic acid, salicylic acid, 4-hydroxy-benzoic acid and phloroglucinol were inducers. Rutin (maximum activity 150 nmol/min/mL after 5 days), quercetin (70 nmol/min/mL, 3 days), phloroglucinol carboxylic acid (60 nmol/min/mL, 3 days), 2-protocatechuoylphloroglucinolcarboxylic acid (50 nmol/min/mL, 5 days), 2,6-dihydroxy-carboxylic acid (90 nmol/min/mL, 7 days) and 2,4-dihydroxy-carboxylic acid (30 nmol/min/mL, 7 days) were demonstrated to be quercetinase inducers. We propose that rutin, quercetin and 2-protocatechuoyl-phloroglucinol carboxylic acid, the product of the reaction catalysed by quercetinase, act as inducers after their catabolic transformation in phloroglucinol carboxylic acid.

Degradation of (+)-catechin by Acinetobacter calcoaceticus MTC 127.

Acinetobacter calcoaceticus MTC 127 was able to grow on catechin and protocatechuic acid (PCA) as sole carbon source. Cells induced with catechin oxidized catechin and PCA at rates higher than cells of uninduced cultures. Two aromatic compounds, PCA and phloroglucinol carboxylic acid (PGCA) were isolated from culture filtrate of cells grown in catechin and characterized by infrared spectrometry and high performance thin-layer chromatography. Moreover, A. calcoaceticus MTC 127 produced high levels of PCA compared to PGCA in the degradation of catechin. Based upon these results, a pathway for the degradation of (+)-catechin in A. calcoaceticus MTC 127 is proposed. Enzymes extracted from catechin-induced culture showed catechin oxygenase (cox) and protocatechuate 3,4-dioxygenase (pcd) activities. Catechin oxygenase was purified by column chromatography and SDS-PAGE analysis showed a single band with an apparent molecular weight of 47 kDa.