Structure Of Phenolic Compounds Research Articles

Valorization of phenolic compounds from brewery wastewater: Performances assessment of ultrafiltration and nanofiltration process with application of HPLC coupled with antioxidant analysis tool

Phenolic-rich brewery alkaline wastewater sustainable valorization with membrane technology was investigated. Intensified process of preselected ceramic 15 kDa ultrafiltration and 200 Da nanofiltration membranes was studied at pH 4, 6.5, 10 and 13.5 to prospect the best operation conditions of phenolic compounds (PC) recovery and water reclamation process regarding fouling inclination, productivity and selectivity performances. Flux-limiting phenomena propensity according to pH were investigated. HPLC coupled with online antioxidant capacity innovative analysis was used to assess PC selectivity behavior and its subsequent impact on antioxidant properties of concentrated wastewater. Flux-limiting phenomena consisted of PC, carbohydrates and proteins pore blocking and cake layer during ultrafiltration and was corroborated to pH acidity. Osmotic pressure due to ions concentration polarization was predominant during nanofiltration and was lower during pH 4 and 13.5 due to membrane characteristics. PC selectivity by ultrafiltration and nanofiltration membranes was determined with compounds size and chemistry, along with pH effect on molecules and membrane charges. The chemical structure of single PC led to differential segregation through the valorization process, and thus to modification of the antioxidant profile of concentrated wastewater. pH 13.5 showed controlled fouling development and advantageous selectivity and productivity performance, and nanofiltration yielded concentrated PC retentate for resource recovery and clarified permeate for water and alkalis reclamation.

Stability and antioxidant activity of phenolic compounds during in vitro digestion.

The impact of phenolic compounds on the human body depended on the type, content, bioavailability, and antioxidant activity. After digestion, different phenolic compounds had different changes of bioavailability and antioxidant activity, which needed to be considered in the application. In this experiment, the structural stability and antioxidant activity of 27 phenolic compounds (phenolic acids, flavonols, flavonoids, and flavanones) were investigated during the in vitro simulated digestion. This experiment eliminated the influence of food matrix, provide a basis for regularity for the changes of phenolic substances in different materials. Results showed that the bioaccessibility of phenolic compounds with different structures varied, and there was a conformational relationship between the structure and stability. After oral digestion, most of the phenolic compounds underwent degradation and the cellular antioxidant activity (CAA) values decreased to a large extent (p<0.05). After gastric digestion, the content (p>0.05) and CAA values (p<0.05) of most phenolic compounds increased. However, after intestinal digestion, the phenolic compounds were degraded to a greater extent, and different structures of phenolic compounds had different changes in CAA values (p<0.05). In general, the CAA values of most phenolic compounds after in vitro digestion were lower than the initial value. The 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-ehylbenzthiazoline-6-sulfonic acid) (ABTS), and ferric reducing antioxidant power (FRAP) values of phenolic acids and flavonols decreased after in vitro simulated digestion (p<0.05), while the values of DPPH, ABTS, and FRAP of most flavonoids (p<0.05) increased. The increased oxygen radical absorption capacity (ORAC) values were found in most phenolic acids, flavonols, and flavonoids (p<0.05), and most flavanones showed unremarkable changes in ORAC values (p>0.05). In general, the changing trend of chemical-based antioxidant activity was consistent with the content of phenolic compounds.

Effect of alkyl chain length and amylose/amylopectin ratio on the structure and digestibility of starch-alkylresorcinols inclusion complexes

Starch can form inclusion complexes with various phenolic compounds. The structure of phenolic compound and the amylose/amylopectin ratio of starch affect their complexing ability and functional properties. In this study, 5-heptadecylresorcinol (ARs-17) and 5-heneicosylresorcinol (ARs-21) were screened and the influences of amylose content on the formation and physicochemical properties of starch-alkylresorcinols (ARs) inclusion complexes were evaluated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC). The digestion curves and logarithm-of-slope (LOS) plots were obtained by in vitro digestion experiments. The results demonstrated that waxy maize starch (WMS) was not able to form inclusion complexes with ARs-17 or ARs-21, however, the possibility of ARs adsorption on amylopectin existed. For normal maize starch (MS), it could only form inclusion complex with ARs-21, and there was uncomplexed ARs in the inclusion complex due to its lower proportion of amylose. High amylose starches (G50 and G80) formed VII-type inclusion complexes with both ARs-17 and ARs-21, especially a small amount of VI-type inclusion complexes was present in ARs-21 inclusion complexes. Meanwhile, the crystallinity, thermal stability, and anti-digestive properties of starch-ARs inclusion complexes increased with the increment of ARs alkyl chain length and amylose content. This study suggested that high amylose starch facilitated stable delivery of ARs, which could improve the bioaccessibility of ARs. • The higher content of amylose and longer alkyl chain length facilitated complexation. • High amylose starch formed both VI and VII inclusion complexes with ARs-21. • In case of insufficient amylose, ARs were likely to adsorb on amylopectin. • The reduced digestion was due to the ordered structure or ARs inhibition on enzymes.

Impact of phenolic compound as activators or inhibitors on the enzymatic hydrolysis of cellulose

The influence of phenolic compounds on the enzymatic hydrolysis of cellulose was studied in depth using spectrophotometric techniques, adsorption analysis and Scanning Electron Microscopy (SEM). In this paper for the first time, both possible interactions between phenolic compounds and the enzyme or the substrate were investigated, with the use of various phenolic compounds, cellulase from T. reesei, and Avicel as cellulose source. Three classes of phenolic compounds have been identified, based on their effect on the hydrolysis of cellulose: inhibitors (quercetin, kaempferol, trans-cinnamic acid, luteolin, ellagic acid), non-inhibitors (p-coumaric acid, rutin, caffeic acid), and activators (ferulic acid, syringic acid, sinapic acid, vanillic acid). Secondly, since various structures of phenolic compounds were tested, a structure – action comprehensive correlation was possible leading to the conclusion that an -OCH3 group was necessary for the activating effect. Finally, based on the adsorption spectra and unique SEM images, a different way of adsorption (either on the enzyme or on the substrate) was noticed, depending on the activating or inhibiting action of the phenolic compound.

Trametes versicolor laccase-assisted oxidative coupling of estrogens: Conversion kinetics, linking mechanisms, and practical applications in water purification

The potential application of fungal laccase-assisted bioremediation for estrogen elimination has caused tremendous attention. Herein, naturally-occurring Trametes versicolor laccase (Tvlac) was capable of significantly removing 17β-estradiol (E2) and 17α-ethynylestradiol (EE2) at pH 5. A lower (or higher) pH caused decline in the velocity constants (kprcs) by obstructing the single-electron oxidation of estrogen at Tvlac T1-Cu site (or intercepting the intramolecular-electron transfer between Tvlac T1-Cu and T2/T3-Cu sites). Humic acid (HA) and natural phenolic compounds (PCs) are omnipresent in water and can influence the conversion kinetics of estrogen in Tvlac-triggered reactions. Compared with HA-free, the kprcs values of E2 and EE2 in presence of HA respectively reduced 58.61%–83.72% and 69.72%–95.62% at different pH levels. Additionally, the kprcs values for estrogen were also hampered obviously by O-dihydroxyphenol structure of model PCs, owning to the created monomeric/polymeric O-quinones inverted estrogen phenoxy radicals. The generated carbon‑carbon/oxygen self-linking aggregates during Tvlac-mediated estrogen oxidative coupling were characterized, and the polymerization mechanisms were speculated. A fluid-bed reactor with cross-linked-entrapped Tvlac in Ca-alginate beads was established to treat E2 and EE2, respectively. Compared with free Tvlac, immobilized Tvlac prominently exhibited a higher pH and temperature stability. Especially, the fluid-bed reactor with immobilized Tvlac could be reused, keeping its high conversion efficiencies of E2 and EE2 in natural water, only changing from 99.2% to 73.6% and from 98.5% to 70.9% after 1 to 5 cycles, respectively. These findings present an alternative immobilized fungal laccase-based clean biotechnology for continuously handling estrogen-contaminated waterbodies at a large-scale.

Green Extraction of Phenolic Compounds from Lotus Seedpod (Receptaculum Nelumbinis) Assisted by Ultrasound Coupled with Glycerol.

Lotus Receptaculum Nelumbinis has been sparking wide research interests due to its rich phenolic compounds. In the present work, ultrasonic-assisted extraction coupled with glycerol was employed to extract phenolic compounds from Receptaculum Nelumbinis and the process was optimized using a response surface methodology with Box-Behnken design (BBD). The optimal conditions for the total phenolic content (TPC) extract were obtained: glycerol concentration of 40%, an extraction temperature of 66 °C, ultrasonic time of 44 min, and the solvent-to-solid ratio of 55 mL/g. Under these optimum extraction conditions, the extraction yield of TPC was 92.84 ± 2.13 mg gallic acid equivalents (GAE) /g. Besides, the antioxidant activities demonstrated the ability of free radical scavenging by four different methods that included 2,2-Diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and reducing activity (RA) were 459.73 ± 7.07, 529.97 ± 7.30, 907.61 ± 20.28, and 983.66 ± 11.80 μmol TE/g, respectively. Six phenolic compounds were identified by ultra-high pressure liquid chromatography combined with triple-time-of-flight mass spectrophotometry (UPLC-Triple-TOF/MS) from the extracts. Meanwhile, Fourier transform infrared (FTIR) was conducted to identify the characteristic functional groups of the extracts and thus reflected the presence of polyphenols and flavonoids. Scanning electron microscopy (SEM) illustrated the microstructure difference of four treatments, which might explain the relationships between antioxidant activities and the structures of phenolic compounds.

The proposed structures of phenolic compounds isolated from Piper betle L. differ from those of the compounds obtained by total synthesis

We describe the syntheses of phenolic compounds, 4-[(1E, 3E, 5E)−6-(4-octyloxyphenyl)hexa-1,3,5-trien-1-yl]benzene-1,2-diol (1) and 3-(n-dodecyloxy) phenol (2), isolated from Piper betle. The triene moiety of 4-[(1E, 3E, 5E)−6-(4-octyloxyphenyl)hexa-1,3,5-trien-1-yl]benzene-1,2-diol was formed via two different methods, the Horner–Wadsworth–Emmons reaction and the McMurry coupling reaction. The spectral data of synthesized compounds show differences with those of reported as the naturally occurring compounds.

Effect of Tea Polyphenols on α-Amylase Activity in Starch Hydrolysis

Tea leaves (Camellia sinensis) contain bioactive compounds that can help prevent certain diseases. In this study, the inhibitory effect of polyphenolic components of different types of tea leaves (green, oolong and black) extracted using different solvents (ethanol, methanol and water) on α-amylase activity of human saliva were investigated in vitro. Total phenolic content (TPC), total flavonoid content (TFC), ferric reducing/antioxidant power and inhibition of free radical scavenging activity by 1,1-diphenyl-2-picrylhydrazyl of the extracts were measured. Content of gallic acid, caffeine and four catechins also were quantified by high performance liquid chromatography. The ethanol extracts had the highest TPC (124.34-231.23 mg gallic acid equivalents (GAE)/g sample), followed by the methanol extracts (124.28-209.76 mg GAE/g sample) and the water extracts (66.89-136.51 mg GAE/g sample). All three solvent extractions of green tea leaves contained the highest TPC, TFC and antioxidant activity, followed by oolong and black tea leaves. Green tea leaves contained higher amounts of catechins than oolong and black tea leaves. All four catechins were detected in green and oolong tea leaves but only gallocatechin gallate was found in black tea leaves. Next, the effect of tea leaves extracts on starch hydrolysis by α-amylase enzyme from human saliva at 37°C was studied. The starches were hydrolyzed with 0.01% enzyme for 240 min and the extent of hydrolysis was determined based on the dextrose equivalent value. The extent of starch hydrolysis by the tea leaves was as follows: green tea > oolong tea > black tea. The low degree of hydrolysis for black tea was due to its strong inhibitory effect on α-amylase activity. Thus, green, oolong and black tea leaves inhibit activity of α-amylase to different degrees due to their differing compositions and structures of phenolic compounds.

Highly efficient extraction of phenolic compounds by use of magnetic room temperature ionic liquids for environmental remediation

A hydrophobic magnetic room temperature ionic liquid (MRTIL), trihexyltetradecylphosphonium tetrachloroferrate(III) ([3C 6PC 14][FeCl 4]), was synthesized from trihexyltetradecylphosphonium chloride and FeCl 3·6H 2O. This MRTIL was investigated as a possible separation agent for solvent extraction of phenolic compounds from aqueous solution. Due to its strong paramagnetism, [3C 6PC 14][FeCl 4] responds to an external neodymium magnet, which was employed in the design of a novel magnetic extraction technique. The conditions for extraction, including extraction time, volume ratio between MRTIL and aqueous phase, pH of aqueous solution, and structures of phenolic compounds were investigated and optimized. The magnetic extraction of phenols achieved equilibrium in 20 min and the phenolic compounds were found to have higher distribution ratios under acidic conditions. In addition, it was observed that phenols containing a greater number of chlorine or nitro substituents exhibited higher distribution ratios. For example, the distribution ratio of phenol ( D Ph) was 107. In contrast, 3,5-dichlorophenol distribution ratio ( D 3,5-DCP) had a much higher value of 6372 under identical extraction conditions. When compared with four selected traditional non-magnetic room temperature ionic liquids, our [3C 6PC 14][FeCl 4] exhibited significantly higher extraction efficiency under the same experimental conditions used in this work. Pentachlorophenol, a major component in the contaminated soil sample obtained from a superfund site, was successfully extracted and removed by use of [3C 6PC 14][FeCl 4] with high extraction efficiency. Pentachlorophenol concentration was dramatically reduced from 7.8 μg mL −1 to 0.2 μg mL −1 after the magnetic extraction by use of [3C 6PC 14][FeCl 4].

COMPARATIVE STUDY OF THE PHENOLIC COMPOSITION IN LENTILS PROCESSED WITH AND WITHOUT ADDITION OF COMMERCIAL TANNASE

The phenolic composition of lentil flour samples, processed with and without the addition of tannase during different times of incubation, 30, 60, 90, 120, 150 and 180 min, were analyzed by high performance liquid chromatography-photodiode array detector-mass spectrometry (HPLC-PAD-MS). Quantitative and qualitative differences in the identified phenolic compounds were observed between the two studied processes, and with respect to the raw lentils. Processed lentils with and without tannase, contain gallic acid, gallic aldehyde and trans-resveratrol, compounds not detected in raw lentils. Quercetin 3-O-rutinoside and luteolin undergo an increase as a consequence of the processes. Analysis of principal components to examine the relationship between time of processing and concentration of phenolics in every lentil sample showed that incubation time is not the only factor that influences the modification of phenolic compounds, but also the activation of the endogenous enzyme together with the addition of commercial tannase, that can bring out synergic and/or antagonist effects depending on the structure of phenolic compound. PRACTICAL APPLICATIONS The application of commercial enzymes in the food industry has been recognized as a useful tool to improve the utilization of nutrients and the quality in raw materials. The success of the enzymatic treatment of legume flours depends on the biochemical reactions developed during the action of enzymes. The objective of this study was to know the modifications in the bioactive phenolic compounds of lentils, comparing the action of natural endogenous enzymes of the substrate with that of commercial tannase, in order to improve the functionality of the obtained lentils flours which could be used as supplement in some foods.

Anticancer Activity of Selected Phenolic Compounds: QSAR Studies Using Ridge Regression and Neural Networks

Phenol and its congeners are known to induce caspase-mediated apoptosis activity and cytotoxicity on various cancer cell lines. Apoptosis, scavenging of radicals, antioxidant, and pro-oxidant characteristics are primarily responsible for the antitumor activities of phenolic compounds. Quantitative structure-activity relationship studies on the cellular apoptosis and cytotoxicity of phenolic compounds have been investigated recently by Selassie and colleagues (J Med Chem; 48:7234, 2005) wherein models were developed for various carcinogenic cell lines. These quantitative structure-activity relationship models are based on few experimentally obtained physicochemical parameters such as Verloop's sterimol descriptor, hydrophobicity, Hammett electronic parameter, and octanol/water partition coefficient. The paper deals with structure-activity relationships of phenols and its derivatives for the development of predictive models from the standpoint of theoretical structural parameters and ridge regression methodology. The quantitative structure-activity relationship studies developed here for the caspase-mediated apoptosis activity and cytotoxicity on murine leukemia cell line (L1210), human promylolytic cell line (HL-60), human breast cancer cell line (MCF-7), parenteral human acute lymphoblastic cells (CCRF-CEM), and multidrug-resistant subline of CCRF-resistant to vinblastine (CEM/VLB) cells utilize physicochemical molecular descriptors calculated solely from the structure of phenolic compounds under investigation along with the descriptors used by Selassie and group. It is seen that such quantitative structure-activity relationships can provide a better quality predictive model for the phenolic compounds. The biological activities of the nine sets of phenolic compounds have been calculated based on ridge regression analysis that clearly gives a better significant correlation compared to the activities predicted by Selassie and co-workers. Counter-propagation artificial neural network studies have been introduced in the present investigation for a better understanding of multidimensional rational patterns in more complex data sets. The counter-propagation artificial neural network studies were performed on the same data set and with the same descriptors as have been carried out in developing ridge regression models and the result of counter-propagation neural network models produces very interesting findings in terms of leave-one-out test. Finally, an attempt has been made for a comparative study of the relative effectiveness of linear statistical methods versus nonlinear techniques, such as counter-propagation neural networks in modeling structure-activity studies of the phenolic compounds.

Adsorption of phenolic compounds from aqueous solutions by aminated hypercrosslinked polymers

Two novel polymers (NJ-1 and NJ-2) were synthesized by chemically modified a hypercrosslinked polymer NJ-0 with dimethylamine and trimethylamine, respectively. The comparison of the adsorption properties of the three polymers toward phenol, resorcin and phloroglucin was made. The study focused on the static equilibrium adsorption behaviors and the adsorption thermodynamics. Freundlich equation was found to fit the adsorption results well. The effect of amino groups introduced onto the surface of the resin and the structure of phenolic compounds on the adsorption were also studied. The hydrogen-bonding interaction and electrostatic interaction could happen between the amino groups and the adsorbates. The adsorption impetus increased as quantity of hydroxyl groups increased, but the adsorption capacity decreased due to the drop of the matching degree of the aperture of resins and the diameter of adsorbate molecules.

A Comparative Study on the Various In Vitro Assays of Active Oxygen Scavenging Activity in Foods

ABSTRACT: Various in vitro assays of active oxygen‐scavenging activity in foods were compared by evaluating the activity of 13 food phenolic compounds and Trolox. 1,1‐Diphenyl‐2‐picrylhydrazyl (DPPH)‐HPLC and liposome oxidation methods were sensitive for these compounds, while deoxyribose oxidation and Randox kit methods were less sensitive. The deoxyguanosine oxidation method could not determine the activity since food polyphenols were pro‐oxidative in this assay. Among these assays, the DPPH‐HPLC method was shown to be the best since the liposome oxidation method is affected more by the structure of phenolic compounds than the DPPH‐HPLC method.

INDUCTION OF A p-COUMAROYL TRIHYDROXY TRITERPENE ACID IN Psylla-INFESTED AND MECHANICALLY DAMAGED PEAR TREES

The pattern of induction and the chemical structure of phenolic compounds in pear trees (Pyrus communis, cv. Conference) that were either infested by pear leaf suckers Psylla pyricola and P. pyri or mechanically damaged, or both, were studied. Chromatographic (HPLC) and mass spectral analysis performed on extracts of leaf samples collected at various time intervals from trees subjected to three treatments demonstrated the induction (and/or amplification) of a phenolic compound, identified as 3-O-trans-p-coumaroyltormentic acid (I). New mass spectrometric data on this phenolic compound are presented. HPLC revealed different peak patterns in the course of the period of Psylla infestation and the lapse of time since mechanical damage was inflicted, compared to a control tree. The new phenolic compound became apparent after 12 hr and reached the highest level 30 days after damage by pear leaf suckers. It was also observed after 24 hr at lower intensity in samples from a mechanically damaged tree and exclusively on day 30 at very low intensity in the leaf extracts from the uninfested control trees. We conclude that damage by pear leaf suckers, and to a lesser extent also mechanical damage, induce the synthesis of the new, late-eluting phenolic compound. We propose that this compound is involved in plant defense against pear leaf suckers.