Oxidation Of Chlorogenic Acid Research Articles

Comparative transcriptome and metabolite survey reveal key pathways involved in the control of the chilling injury disorder superficial scald in two apple cultivars, 'Granny Smith' and 'Ladina'.

The low temperature normally applied to prevent fruit decay during the storage of apples, can also triggers the onset of a chilling injury disorder known as superficial scald. In this work, the etiology of this disorder and the mechanism of action of two preventing strategies, such as the application of 1-MCP (1-methylcyclopropene) and storage at low oxygen concentration in 'Granny Smith' and 'Ladina' apple cultivars were investigated. The metabolite assessment highlighted a reorganization of specific metabolites, in particular flavan-3-ols and unsaturated fatty acids, while the genome-wide transcriptomic analysis grouped the DEGs into four functional clusters. The KEGG pathway and GO enrichment analysis, together with the gene-metabolite interactome, showed that the treatment with 1-MCP prevented the development of superficial scald by actively promoting the production of unsaturated fatty acids, especially in 'Granny Smith'. 'Ladina', more susceptible to superficial scald and less responsive to the preventing strategies, was instead characterized by a higher accumulation of very long chain fatty acids. Storage at low oxygen concentration stimulated a higher accumulation of ethanol and acetaldehyde together with the expression of genes involved in anaerobic respiration, such as malate, alcohol dehydrogenase and pyruvate decarboxylase in both cultivars. Low oxygen concentration, likewise 1-MCP, through a direct control on ethylene prevented the onset of superficial scald repressing the expression of PPO, a gene encoding for the polyphenol oxidase enzyme responsible of the oxidation of chlorogenic acid. Moreover, in 'Granny Smith' apple, the expression of three members of the VII subgroups of ERF genes, encoding for elements coordinating the acclimation process to hypoxia in plants was observed. The global RNA-Seq pattern also elucidated a specific transcriptomic signature between the two cultivars, disclosing the effect of the different genetic background in the control of this disorder.

An effective electrochemical detection of chlorogenic acid in real samples: Flower-like ZnO surface covered on PEDOT:PSS composites modified glassy carbon electrode

Zinc oxide (ZnO) possessing the flower-like structure with the surface covered by Poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) polymer was synthesized successfully through the one-pot chemical synthesis technique. As-synthesized ZnO@PEDOT:PSS modified glassy carbon electrode (GCE) was engaged for effective electrochemical oxidation of chlorogenic acid (CGA). The uniform encapsulation of PEDOT:PSS polymer was confirmed by adopting HR-TEM and FE-SEM method. The physicochemical properties of the as-synthesized composite were studied by using various analytical techniques and the results seem more satisfactorily. Specifically, ZnO@PEDOT:PSS-GCE towards CGA oxidation shows wide-linear range, high sensitivity, limits of detection, and limits of quantification values are 0.03–476.2 μM, 29.38 μA μM−1 cm-2, 0.02 μM, and 0.3 μM, respectively. Furthermore, the potential of ZnO@PEDOT:PSS-GCE for the effectiveness determination of CGA is accessed by using coffee powder and soft drink as real-time samples.

Antimicrobial mechanism of reaction products of Morus notabilis (mulberry) polyphenol oxidases and chlorogenic acid

Herein, five polyphenol oxidases (PPOs) obtained from Morus notabilis (Mn) were characterized. Chlorogenic acid was the most readily oxidized substrate by these MnPPOs, and the products derived from the oxidation of chlorogenic acid by MnPPOs were tested for antimicrobial activity. The results showed that products of the five MnPPOs exhibited good inhibitory effects against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Sclerotinia sclerotiorum, and Botrytis cinerea. Because the products of MnPPO1 exhibited the strongest antimicrobial activity, the antimicrobial mechanism of these products was explored. The results showed that the products of MnPPO1 increased cell membrane permeability and chitinase and β-1,3-glucanase activities.

Surface enhancement of porous alumina microfibers toward electrochemical sensing of chlorogenic acid

Porous alumina microfibers with a diameter of 125 nm were prepared through hydrothermal reaction in urea solution using aluminium nitrate as the precursor, and characterized using transmission electron microscopy and scanning electron microscopy. The mechanism of oxidation of chlorogenic acid was examined using cyclic voltammetry, indicating a reversible two-electron process. Compared with the bare carbon paste electrode (CPE), the oxidation signals of chlorogenic acid were greatly enhanced with the alumina microfiber-modified CPE. Chronocoulometry experiments indicated that the accumulation of chlorogenic acid on the surface of the alumina microfibers was obviously improved relative to that on the bare electrode, which is attributed to the numerous micropores and regular fiber-like structures. Based on the signal amplification ability of the porous alumina microfibers, a novel electrochemical sensing platform was developed for chlorogenic acid. The linear range was 10–2000 μg L−1, and the limit of detection was evaluated to be 5.0 μg L−1. The practical application of this new method was demonstrated using honeysuckle and soft drink samples. The results were consistent with the values obtained by high-performance liquid chromatography.

A novel AuNPs-doped COFs composite as electrochemical probe for chlorogenic acid detection with enhanced sensitivity and stability

In this work, novel gold nanoparticles-doped TAPB-DMTP-COFs (TAPB, 1,3,5-tris(4-aminophenyl)benzene; DMTP, 2,5-dimethoxyterephaldehyde; COFs, covalent organic frameworks) composite was successfully prepared via COFs as the host matrix to support the growth of gold nanoparticles. With the strong electrostatic interaction between gold nanoparticles and unsaturated amine group present on TAPB-DMTP-COFs, the gold nanoparticles were successfully immobilized onto the surface of TAPB-DMTP-COFs under vigorously stirring. Then, this novel composite was used to constitute an advanced electrochemical sensor and presented a good electrocatalytic activity toward the oxidation of chlorogenic acid (CGA) in the phosphate buffer solution (pH 7.0). After a series of experiments, this electrochemical sensor displays a wide linear range of 1.0 × 10−8 – 4.0 × 10−5 mol L−1, low detection limit of 9.5 × 10−9 mol L−1 as well as a good repeatability of 4.1% in 2.0 × 10−5 mol L−1 CGA after ten scanning rounds. Moreover, the sensor exhibits an excellent stability and maintains its catalytic activity at least 100 cycles. Our work not only provides a simple way to detect CGA quantitatively in real samples, but paves a new platform for COFs-based composite in biosensor.

Protection of protein from ruminal degradation by alkali-induced oxidation of chlorogenic acid in sunflower meal.

Lactating ruminants require an adequate supply of absorbable amino acids for the synthesis of milk protein from two sources, that is crude protein (CP) synthesized microbially in the rumen and ruminally undegraded CP (RUP) from feed which can both be digested in the small intestine. Several chemical and physical methods have been identified as being effective in increasing the proportion of RUP of total CP of a feedstuff, yet there is a continuing need for developing and establishing methods which protect feed protein from ruminal degradation with acceptable expenditure of labour and other costs. The objective of this study was to identify and quantify effects of and interactions between chlorogenic acid and protein in solvent-extracted sunflower meal (SFM) as induced by alkali treatment. Response surface methodology was employed to investigate the influence of pH, reaction time and drying temperature on the resulting SFM and, subsequently, its protein value for ruminants estimated from laboratory values. For this purpose, alkali-treated SFM was subjected to a fractionation of feed CP according to the Cornell net carbohydrate and protein system as a basis for estimating RUP at different assumed ruminal passage rates (Kp ). To estimate the intestinal digestibility of the treated SFM and its RUP, a three-step enzymatic in vitro procedure was applied. Alkaline treatment of SFM increased RUP values with factors ranging from approximately 3 (Kp =.08/hr) to 12 (Kp =.02/hr). Furthermore, the intestinal digestibility of the alkali-treated SFM was enhanced by approximately 10% compared to untreated SFM. Increasing pH and reaction time led to both increasing RUP values and intestinal digestibility. In conclusion, a targeted alkaline treatment of naturally occurring compounds in feedstuffs might be a promising approach to provide high-RUP feeds for ruminants which, at the same time, have improved intestinal digestibility values.

Chlorogenic Acid Oxidation and Its Reaction with Sunflower Proteins to Form Green-Colored Complexes.

Sunflower seeds are used to produce oil for human consumption, but its protein meal by-product has long been used as animal feed. Formation of green-colored complexes through oxidized chlorogenic acid(CGA)-protein interactions is a primary reason why defatted sunflower protein has not been widely utilized by the food industry. Sunflower protein possesses many properties that make it an appealing alternative protein source from both a marketing and formulation perspective, including its low cost, absence of major allergens, low antitrypsin inhibitors, and its status as both vegan and "clean" label friendly. With the global demand for sunflower oil and novel protein sources expected to increase and waste recovery a concern for many, providing uses for the sunflower meal and its fiber and polyphenol components would provide added value to by-products from sunflower oil processing. This review addresses the unique green pigmentation associated with the interaction of sunflower protein and oxidized CGA by outlining the sunflower oil and protein meal market, CGA reactions contributing to greening, methods for CGA extraction, and the effect of processing on sunflower protein quality and the greening reaction. This review also addresses potential food applications of sunflower protein-based ingredients, such as addition of texturized protein to food products; a microencapsulation matrix for antioxidants; edible, flexible biodegradable films; and even use of sunflower butter as an alternative to peanut butter where the green color is not considered undesirable. Continued studies are needed to make sunflower-based products and CGA-extraction processes available across the global marketplace.

Analysis of Chlorogenic Acid Oxidation Pathway in Simulated Enzymatic Honeysuckle Browning System by High Performance Liquid Chromatography and Mass Spectrometry

Purpose: To investigate the pathways involved in the oxidation of chlorogenic acid (CA) and phenol metabolism in honeysuckle buds. Methods: A model that mimics CA oxidation by honeysuckle polyphenol oxidase (PPO) by controlling the reaction temperature or reaction duration was employed, and the resulting products were analyzed by high-performance liquid chromatography followed by mass spectrometry (LC-MS). Results: The pathway of CA oxidation by PPO in honeysuckle involves CA, hydroxyl - CA, CA-oquinone derivatives, and CA-p-quinone derivatives. Conclusion: CA oxidation and the enzymatic browning reaction significantly impact the quality of honeysuckle and other fresh agricultural products. Keywords: Honeysuckle, Chlorogenic acid, Enzymatic browning, Mimic system, Oxidation pathway, High-performance liquid chromatography-mass spectrometry

Reactions of polyphenols in masticated apple fruit with nitrite under stomach simulating conditions: Formation of nitroso compounds and thiocyanate conjugates

By the ingestion of fresh apple fruit, it is masticated squeezing apple juice into the oral cavity and the juice is mixed with saliva. The mixture of saliva and apple juice is swallowed into the stomach where the pH is around 2. This paper deals with the reactions of polyphenols in the juice obtained by mastication of apple fruit with salivary nitrite under acidic conditions. The concentrations of catechins, procyanidins, and chlorogenic acid in the apple juice were approximately 55, 55, and 170μM, respectively, and the polyphenols were oxidized by salivary nitrite under conditions of the stomach. Rates of the oxidation increased in order chlorogenic acid<catechins<procyanidins. The oxidation of catechins and procyanidins resulted in the formation of the nitroso compounds, and the oxidation of chlorogenic acid resulted in the formation of the thiocyanate conjugate. The production of dinitroso compounds is proposed to be due to the addition of nitric oxide (NO) to radicals of catechins and procyanidins. As the mechanism of thiocyanate conjugate formation, reaction of o-quinone of chlorogenic acid with a salivary component thiocyanate is proposed, and the formation of the thiocyanate conjugate is discussed from the point of detoxification of chlorogenic acid quinone.

Electrochemical Behavior of Chlorogenic Acid at a Boron‐Doped Diamond Electrode and Estimation of the Antioxidant Capacity in the Coffee Samples Based on Its Oxidation Peak

In this study, an electroanalytical methodology for the determination of chlorogenic acid (CGA) was achieved at a boron-doped diamond electrode under adsorptive transfer stripping voltammetric conditions. The values obtained for CGA were used to estimate the antioxidant properties of the coffee sample based on CGA oxidation. By using square-wave stripping mode, the compound yielded a well-defined voltammetric response at +0.49 V with respect to Ag/AgCl in Britton-Robinson buffer at pH 3.0 (after 120 s accumulations at a fixed potential of 0.40 V). At the optimum experimental conditions, linear calibration curve is obtained within the concentration range of 0.25 to 4.0 μg mL⁻¹ with the limit of detection 0.049 μg mL⁻¹ . The developed protocol was successfully applied for the analysis of antioxidant capacity in the coffee products such as Turkish coffee and instant coffee.

Characterisation of phenol oxidase and peroxidase from maize silk

Silk of some maize genotypes contains a high level of phenolics that undergo enzymatic oxidation to form quinones, which condense among themselves or with proteins to form brown pigments. Two phenolic oxidizing enzymes, peroxidase (POD; EC 1.11.1.7) and polyphenol oxidase (PPO; EC 1.10.3.1), from maize (Zea mays L.) silk were characterised with respect to their preferred substrate, different isoforms and specific effectors. One browning silk sample with high, and two non-browning samples with low phenolic content were investigated. Although POD oxidizes a wide range of phenolic substrates in vitro, its activity rate was independent of silk phenolic content. PPO activity, detected with o-diphenolic substrates, was abundant only in browning silk, and low or absent in non-browning silk. Pollination increased POD but not PPO activity. Isoelectric-focusing (IEF) and specific staining for POD and PPO showed a high degree of polymorphism that varied with silk origin. The IEF pattern of POD revealed a number of anionic and several cationic isoenzymes, with the most pronounced having neutral pI 7 and a basic isoform with pI 10. Detected isoforms of PPO were anionic, except for one neutral form found only in browning silk, and occupied positions different from those of POD. Different inhibitory effects of NaN(3), EDTA, KCN, and L-cysteine, as well as different impacts of a variety of cations on the oxidation of chlorogenic acid, mediated by PPO or POD, were detected. The findings are discussed in terms of a possible roles of these enzymes in defence and pollination.

Chlorogenic Acid Oxidation by a Crude Peroxidase Preparation: Biocatalytic Characteristics and Oxidation Products

Plant food residues including trimmings and peels might contain a range of enzymes capable of transforming bio-organic molecules, and thus they may have potential uses in several biocatalytic processes, including green organic synthesis, modification of food physicochemical properties, bioremediation, etc. Although the use of bacterial and fungal enzymes has gained interest in studies pertaining to biocatalytic applications, plant enzymes have been given less attention or even disregarded. In this view, this study aimed at investigating the use of a crude peroxidase (POD) preparation from onion solid by-products for oxidizing chlorogenic acid (CGA), a widespread phenolic acid, various derivatives of which may occur in foods and food wastes. The highest enzyme activity was observed at a pH value of 4, but considerable activity was also observed at pH 2. Favorable temperatures for increased activity varied between 5 and 20 °C. Liquid chromatography–mass spectrometry analysis of a POD-treated CGA solution showed the formation of two major oxidation products, which were tentatively identified as CGA dimers.

Biosensor for chlorogenic acid based on an ionic liquid containing iridium nanoparticles and polyphenol oxidase

A biosensor based on the ionic liquid, 1- n-butyl-3-methylimidazolium hexafluorophosphate containing dispersed iridium nanoparticles (Ir-BMI.PF 6) and polyphenol oxidase was constructed. This enzyme was obtained from the sugar apple ( Annona squamosa), immobilized in chitosan ionically crosslinked with oxalate. The biosensor was used for determination of chlorogenic acid by square wave voltammetry. The polyphenol oxidase catalyzes the oxidation of chlorogenic acid to the corresponding o-quinone, which is electrochemically reduced back to this substance at +0.25 V vs. Ag/AgCl. Under optimized operational conditions the chlorogenic acid concentration was linear in the range of 3.48 × 10 −6 to 4.95 × 10 −5 mol L −1 with a detection limit of 9.15 × 10 −7 mol L −1. The biosensor was applied in the determination of chlorogenic acid in organic and decaffeinated coffee and the results compared with those obtained using the capillary electrophoresis method. The recovery study for chlorogenic acid in these samples gave values of 93.2–105.7%.

Biosensors based on bean sprout homogenate immobilized in chitosan microspheres and silica for determination of chlorogenic acid

Biosensors for the square wave voltammetric determination of chlorogenic acid were developed by immobilization of a homogenate of fresh bean sprouts ( Vigna radiata) in chitosan microspheres (biosensor I) and silica (biosensor II) crosslinked with glutaraldehyde and epichlorohydrin. The bean sprout tissue acts as a source of peroxidase which, in the presence of hydrogen peroxide, catalyzes the oxidation of chlorogenic acid. The electrochemical reduction of this product was obtained at a potential of +0.18 V (biosensor I) and at a potential of +0.22 V (biosensor II). The chlorogenic acid concentration was linear in the range of 4.89 × 10 −6 to 3.20 × 10 −4 M (biosensor I) and 4.89 × 10 −6 to 4.85 × 10 −5 M (biosensor II) with detection limits of 8.02 × 10 −7 and 8.52 × 10 −7 M, respectively. These biosensors demonstrated long-term stability (4 months; 300 determinations) and reproducibility, with a relative standard deviation of 3.5% (biosensor I) and 1.5% (biosensor II). The recovery of chlorogenic acid from four coffee samples ranged from 96.5 to 102.6% (biosensor I) and 91.3 to 115.5% (biosensor II). Results obtained for the determination of chlorogenic acid in these samples using the proposed biosensors and those obtained using the capillary electrophoresis method are in agreement at the 95% confidence level.

Determination of chlorogenic acid by flow injection irreversible biamperometry

A flow injection irreversible biamperometric method for the determination of chlorogenic acid is described. The proposed method is based on the electrochemical oxidation of chlorogenic acid at pretreated platinum electrode and the reduction of permanganate at another electrode to form an irreversible biamperometric detection system. Under the external potential difference (Δ E) of 0 V, in the 0.05 mol/L sulfuric acid, chlorogenic acid can be determined over the range 0.8–120 mg/L with a sample measurement frequency of 80 samples/h. The detection limit is 0.18 mg/L. The proposed method exhibits the satisfactory reproducibility with a relative standard derivation (R.S.D.) of 2.21% for 19 successive determinations of 40 mg/L.

Kinetic Characterization of the Oxidation of Chlorogenic Acid by Polyphenol Oxidase and Peroxidase. Characteristics of theo-Quinone

Chlorogenic acid is the major diphenol of many fruits, where it is oxidized enzymatically by polyphenol oxidase (PPO) or peroxidase (POD) to its o-quinone. In spectrophotometric studies of chlorogenic acid oxidation with a periodate ratio of [CGA]0/[IO4-]0 < 1 and [CGA]0/[IO4-]0 > 1, the o-quinone was characterized as follows: lambda(max) at 400 nm and epsilon = 2000 and 2200 M-1 cm-1 at pH 4.5 and 7.0, respectively. In studies of o-quinone generated by the oxidation of chlorogenic acid using a periodate at ratio of [CGA]0/[IO4-]0 > 1, a reaction with the remaining substrate was detected, showing rate constants of k = 2.73 +/- 0.17 M-1 s-1 and k' = 0.05 +/- 0.01 M-1 s-1 at the above pH values. A chronometric spectrophotometric method is proposed to kinetically characterize the action of the PPO or POD on the basis of measuring the time it takes for a given amount of ascorbic acid to be consumed in the reaction with the o-quinone. The kinetic constants of mushroom PPO and horseradish POD are determined.

Purification and Characterization of Chlorogenic Acid Oxidase from Edible Burdock (Arctium lappa L.)

The spectral profiles of edible burdock extract during browning reaction suggested that the oxidation of chlorogenic acid and its analogues mainly causes enzymatic browning in edible burdock. Polyphenol oxidase (PPO) was purified-16. 6-fold with a recovery rate of 21% using chlorogenic acid as substrate. The purified enzyme appeared as a single band on PAGE and SDS-PAGE. The molecular weight of the enzyme was estimated to be about 41, 000 and 40, 000 by gel filtration and SDS-PAGE, respectively. The purified enzyme quickly oxidized chlorogenic acid and (-) -epicatechin. The Km values of the enzyme were 0.4 mM for chlorogenic acid (pH 5. 0, 20°C) and 2.7 mM for (-) -epicatechin (pH 8.0, 20°C). The optimum pHs were 5.0 for chlorogenic acid oxidase (ChO) and 8.0 for (-) -epicatechin oxidase (EpO). In the pH range from 5 to 8, both ChO and EpO activities were quite stable at 4°C for 22 h. The optimum temperature of both activities was 20°C. Both activities were 50% inactivated after a heat treatment at 45°C for 30 min. Both activities were strongly inhibited by L-ascorbic acid and L-cysteine at 5 mM.

Isolation of a latent polyphenol oxidase from loquat fruit ( Eriobotrya japonica Lindl.): Kinetic characterization and comparison with the active form

Polyphenol oxidase (PPO) has been extracted from both soluble and particulate fractions of loquat fruit ( Eriobotrya japonica Lindl. cv. Algerie). The soluble PPO (20% of total activity) was partially purified 3.3-fold after ammonium sulfate fractionation being in its active state. The particulate PPO fraction (80% of total activity) was purified to homogeneity in a latent form being activable by sodium dodecyl sulfate (SDS). The enzyme was purified 40.0-fold with a total yield of 15.3% after extraction by phase partitioning in Triton X-114 followed by three chromatographic steps. The molecular weight was estimated to be about 59.2 and 61.2 kDa by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) and gel filtration chromatography, respectively, indicating that latent PPO is a monomer. Latent PPO catalyzed the oxidation of chlorogenic acid (CA) at a rate 50-fold faster than that of 4- tert-butylcatechol (TBC) but the soluble active counterpart only twice. Both PPOs exhibited similar K m values for TBC but K m for CA was 5-fold higher for the latent than for the active soluble PPO. Other kinetic characteristics, including sensitivity to inhibitors, substrate specificity, thermal stability, temperature, and pH profiles, were quite different between both PPOs. These results provide strong evidences that the soluble active and the particulate latent are different forms of PPO in loquat fruit flesh. The results suggest that the major PPO form for the oxidation of CA, leading to enzymatic browning under physiological conditions, is the latent one.

Electrochemistry of chlorogenic acid: experimental and theoretical studies

Cyclic voltammetry, chronoamperometry and rotating disk electrode voltammetry as well as quantum chemical methods, are used for electrochemical study of chlorogenic acid, as an important biological molecule. The standard formal potential, diffusion coefficient, and heterogeneous electron transfer rate constant of chlorogenic acid in aqueous solution are investigated. Acidic dissociation constant of chlorogenic acid is also obtained. Quantum mechanical calculations on oxidation of chlorogenic acid in aqueous solution, using density functional theory are presented. The change of Gibbs free energy and entropy of oxidation of chlorogenic acid are calculated using thermochemistry calculations. The calculations in aqueous solution are carried out with the use of polarizable continuum solvation method. Theoretical standard electrode potential of chlorogenic acid is achieved to be 0.580 V versus standard calomel electrode (SCE) which is in agreement with the experimental value of 0.617 V obtained experimentally in this work. The difference is consistent with the values we previously reported for other quinone derivatives.

Changes in the carotenoid content of apricot (Prunus armeniaca, var Bergeron) during enzymatic browning: β-carotene inhibition of chlorogenic acid degradation.

Considering the numerous beneficial effects in human health ascribed to carotenoids, studies were performed to investigate the modification of carotenoid amount and composition during apricot enzymatic browning. First works on bruised apricot purees have shown a trans-β-carotene isomerisation (20%) induced by enzymatic browning. To clarify this isomerisation, oxidation of chlorogenic acid in presence of trans-β-carotene, catalysed by purified apricot polyphenoloxidase (PPO), was followed by HPLC and polarography. Isomerisation rate of trans-β-carotene in its cis isomer was found to increase with chlorogenic acid concentration. Moreover, trans-β-carotene was shown to be a potent inhibitor of phenol degradation. This inhibition was partially ascribed to PPO inhibition (non-competitive inhibitor towards phenol with an apparent Ki close to 0.5 mM, a mixed type inhibitor towards oxygen with an apparent Ki close to 0.15 mM). The additional inhibition was explained by non-enzymatic reactions involving trans-β-carotene and chlorogenic acid o-quinones and leading to phenol regeneration and carotene isomerisation. © 2000 Society of Chemical Industry.