Classes Of Phenolic Compounds Research Articles

Characterization and discrimination of phenolic compounds using Fourier transform Raman spectroscopy and chemometric tools

Description of the subject. Phenolic compounds (PCs) are the most abundant secondary metabolites in plants. This work was part of a study that sought to develop rapid screening FT-Raman methods for identifying and quantifying classes and/or types of PCs in the dry extracts of plant products. Objectives. Fourier transform Raman spectroscopy (FT-Raman) coupled with chemometric tools was used to characterize and discriminate four families of phenolic compounds: two important classes of phenolic acids, hydroxybenzoic and hydroxycinnamic acids, as well as their derivatives and flavonoids. Method. For this study, 25 standards of phenolic compounds were used (47 standards in total, taking account of the different brands). Repeatability and reproducibility studies were conducted to verify the Raman assignments of gallic acid. Raman characterization with the most significant spectral bands of phenolic compounds was done using spectra ranging from 1,800 to 50 cm-1. A Fisher test was applied to pre-processed Raman spectra (SNV) and 20 Raman scattering signals were used to differentiate each class of phenolic compounds. Results. Hydroxybenzoic acids, hydroxycinnamic acids, their derivatives and flavonoids have been characterized by Raman spectroscopy; bands have been identified and differentiated within and between groups. Conclusions. The scattering intensities located around 1,600-1,699, 1,300-1,400 and below 200 cm-1 were responsible for differentiating 100% of phenolic compound families, classes and subclasses.

Quantification of three phenolic classes and total phenolic content of propolis extracts using a single UV-vis spectrum

This work presents a methodology for simultaneously measuring the total content of three classes of phenolic compounds (hydroxybenzoic acids, hydroxycinamic acids and flavonoids), as well the total phenolic content using a single UV-vis spectrum. To test the methodology, samples of propolis were used. Firstly, an experimental design based in the Response Surface Methodology established that the best hydroethanolic solution for propolis phenolic compounds extraction had 80% of ethanol. Secondly, calibration models were developed with multiple linear regression, coupled with the leaps algorithm for variable selection, using UV-vis spectra of mixed standard solutions (gallic acid, ferulic acid and quercetin mixtures), all with orthogonal concentrations established by a multilevel fractional factorial design. The model’s estimation and prediction performance had linearity between predicted and expected concentration values, with slope ranging from 0.996–1.04 and determination coefficients higher than 0.995. A quality control solution presented acceptable repeatability and accuracy (relative standard deviation percentage and percentage relative error were lower than 4.8%). Analysis of propolis phenolic compounds extracts showed acceptable precision (relative standard deviation percentages lower than 1.6%) and acceptable accuracy (recoveries assays ranged between 98 and 112%). Overall, the present multi-parametric analytical technique can be a first approach for chemical characterization of phenolic compounds extracts, such as that obtained from the propolis samples, considering its advantages of simplicity, rapidity, precision and accuracy. Moreover, this methodology can be adapted to other sample matrices, provided that the typical UV-vis absorption spectra of their classes of phenolic compounds shows partial overlapping, allowing multivariate calibration.

Toxicity of phenolipids: Protocatechuic acid alkyl esters trigger disruption of mitochondrial membrane potential and caspase activation in macrophages

Phenolipids are a class of phenolic compounds with a lipidic moiety that have been receiving increasing attention due to their promising biological activities; however data regarding their toxicity and mechanism of action are scarce. A series of 11 phenolipids consisting of alkyl esters derivatives of the natural molecule protocatechuic acid was synthesized and evaluated against a panel of cancer and non-cancer cell lines. The macrophage cell line RAW 264.7, widely used as a tool for screening anti-inflammatory drugs, was more susceptible to the toxicity of these molecules than human cancer cells, reason for which mechanist studies were conducted. The parent molecule was not toxic up to 100μM, however structural modifications by inclusion of carbon side chains resulted in increased toxicity, compounds bearing 8–14 carbons being the most toxic and displaying IC50 in the nanomolar range. Mechanistic studies showed that phenolipids elicit chromatin condensation, loss of cell viability and disruption of mitochondrial membrane potential (ΔΨm), increased reactive oxygen species (ROS) and activation of caspase-9/3, thus pointing to the involvement of mitochondria in the programmed cell death process taking place.This is the first study addressing the toxicity and mechanism of action of protocatechuic acid derivatives, which is relevant in light of the recent interest in these molecules.

Phenolic compounds profile and antioxidant properties of six sweet cherry (Prunus avium) cultivars

Sweet cherry (Prunus avium) fruits are a nutritionally important food rich in dietary phenolic compounds. The aim of this study was to investigate the phenolic profile and chemometric discrimination of fruits from six cherry cultivars using a quantitative metabolomics approach, which combine non-targeted mass spectrometry and chemometric analysis. The assessment of the phenolic fingerprint of cherries allowed the tentative identification of 86 compounds. A total of 40 chlorogenic acids were identified in cherry fruit, which pointed out hydroxycinnamic acid derivatives as the main class of phenolics by number of compounds. Among the compounds detected, 40 have been reported for the first time in sweet cherry fruit. Hydroxycinnamic acids are also the quantitatively most represented class of phenolic compounds in the cherry cultivars with the exception of Lapins and Durone della Marca where the most representative class of phenolic compounds were anthocyanins and flavan-3-ols, respectively. This non-targeted approach allowed the tentative identification of the cultivar-compound relationships of these six cherry cultivars. Both anthocyanins and colorless phenolic compounds profile appeared to be cultivar-dependent. In detail, anthocyanins and flavonols patterns have the potential to be used for the determination of a varietal assignment of cherries.

Hazelnut (Corylus avellana L.) Shells Extract: Phenolic Composition, Antioxidant Effect and Cytotoxic Activity on Human Cancer Cell Lines.

Hazelnut shells, a by-product of the kernel industry processing, are reported to contain high amount of polyphenols. However, studies on the chemical composition and potential effects on human health are lacking. A methanol hazelnut shells extract was prepared and dried. Our investigation allowed the isolation and characterization of different classes of phenolic compounds, including neolignans, and a diarylheptanoid, which contribute to a high total polyphenol content (193.8 ± 3.6 mg of gallic acid equivalents (GAE)/g of extract). Neolignans, lawsonicin and cedrusin, a cyclic diarylheptanoid, carpinontriol B, and two phenol derivatives, C-veratroylglycol, and β-hydroxypropiovanillone, were the main components of the extract (0.71%–2.93%, w/w). The biological assays suggested that the extract could be useful as a functional ingredient in food technology and pharmaceutical industry showing an in vitro scavenging activity against the radical 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) (EC50 = 31.7 μg/mL with respect to α-tocopherol EC50 = 10.1 μg/mL), and an inhibitory effect on the growth of human cancer cell lines A375, SK-Mel-28 and HeLa (IC50 = 584, 459, and 526 μg/mL, respectively). The expression of cleaved forms of caspase-3 and poly(ADP-ribose) polymerase-1 (PARP-1) suggested that the extract induced apoptosis through caspase-3 activation in both human malignant melanoma (SK-Mel-28) and human cervical cancer (HeLa) cell lines. The cytotoxic activity relies on the presence of the neolignans (balanophonin), and phenol derivatives (gallic acid), showing a pro-apoptotic effect on the tested cell lines, and the neolignan, cedrusin, with a cytotoxic effect on A375 and HeLa cells.

Dietary nutritional profile and phenolic compounds consumption in school children of highlands of Argentine Northwest

The objective of this work was to assess dietary patterns and consumption of phenolic compounds from fruits and vegetables byschoolchildren of high altitude regions from northwest of Argentina. A nutritional survey including food-frequency consumption, 24-h dietary recall and anthropometric measurements was applied to 241 children from 6 to 12years old. The amounts of the different classes of phenolic compounds were established from Food Composition Tables available in phenol-explorer website. Statistics analyses were performed using IBM SPSS 20.0. Nutritional status assessment showed underweight (2.2%), low weight (12.7%), overweight (12.7%) and obesity (7.4%). Mean intake of phenolic compounds was 412mg/day. Most consumed foods were infusions and sugar products, consumption of vegetables, fruits and dairy products were low compared to recommendations for this age. Considering that polyphenols have protective health effects, its low consumption could be a risk of development of chronic non communicable diseases.

Fruit as Potent Natural Antioxidants and Their Biological Effects.

The consumption of fruit has increased in the last 20 years, along with the growing recognition of its nutritional and protective values. Many of the benefits of a diet rich in fruit are attributed to the presence of different bioactive substances, such as vitamins, carotenoids and phenolic compounds. Flavanoids, a class of phenolic compounds, present particular antioxidant activity and thus provide protection against cellular damage caused by reactive oxygen species. Research suggests that an increased intake of plant foods is associated with a reduced incidence of chronic disease. There is currently a great deal of interest in the study of antioxidants, in particular due to the discovery of the damaging effects of free radicals to the body. Thus, this review aims to address the beneficial effects of the antioxidants present in fruits, on the neutralization of reactive species and the reduction of any damage they may cause.

Wild Prunus Fruit Species as a Rich Source of Bioactive Compounds

Sugars, organic acids, carotenoids, tocopherols, chlorophylls, and phenolic compounds were quantified in fruit of 4 wild growing Prunus species (wild cherry, bird cherry, blackthorn, and mahaleb cherry) using HPLC-DAD-MSn. In wild Prunus, the major sugars were glucose and fructose, whereas malic and citric acids dominated among organic acids. The most abundant classes of phenolic compounds in the analyzed fruit species were anthocyanins, flavonols, derivatives of cinnamic acids, and flavanols. Two major groups of anthocyanins measured in Prunus fruits were cyanidin-3-rutinoside and cyanidin-3-glucoside. Flavonols were represented by 19 derivatives of quercetin, 10 derivatives of kaempferol, and 2 derivatives of isorhamnetin. The highest total flavonol content was measured in mahaleb cherry and bird cherry, followed by blackthorn and wild cherry fruit. Total phenolic content varied from 2373 (wild cherry) to 11053 mg GAE per kg (bird cherry) and ferric reducing antioxidant power antioxidant activity from 7.26 to 31.54 mM trolox equivalents per kg fruits.

Extraction of cocoa proanthocyanidins and their fractionation by sequential centrifugal partition chromatography and gel permeation chromatography.

Cocoa beans contain secondary metabolites ranging from simple alkaloids to complex polyphenols with most of them believed to possess significant health benefits. The increasing interest in these health effects has prompted the need to develop techniques for their extraction, fractionation, separation, and analysis. This work provides an update on analytical procedures with a focus on establishing a gentle extraction technique. Cocoa beans were finely ground to an average particle size of <100μm, defatted at 20°C using n-hexane, and extracted three times with 50% aqueous acetone at 50°C. Determination of the total phenolic content was done using the Folin-Ciocalteu assay, the concentration of individual polyphenols was analyzed by electrospray ionization high performance liquid chromatography-mass spectrometry (ESI-HPLC/MS). Fractions of bioactive compounds were separated by combining sequential centrifugal partition chromatography (SCPC) and gel permeation column chromatography using Sephadex LH-20. For SCPC, a two-phase solvent system consisting of ethyl acetate/n-butanol/water (4:1:5, v/v/v) was successfully applied for the separation of theobromine, caffeine, and representatives of the two main phenolic compound classes flavan-3-ols and flavonols. Gel permeation chromatography on Sephadex LH-20 using a stepwise elution sequence with aqueous acetone has been shown for effectively separating individual flavan-3-ols. Separation was obtained for (-)-epicatechin, proanthocyanidin dimer B2, trimer C1, and tetramer cinnamtannin A2. The purity of alkaloids and phenolic compounds was determined by HPLC analysis and their chemical identity was confirmed by mass spectrometry.

Identification and characterization of phenolic compounds in hydromethanolic extracts of sorghum wholegrains by LC-ESI-MSn

Hydromethanolic extracts of brown, red, and white sorghum whole grains were analysed by LC-MSn in negative ESI mode within the range m/z 150–550amu. Besides the flavonoids already reported in sorghum, a number of flavonoids were also identified in the sorghum grain for the first time, including flavanones, flavonols and flavanonols, and flavan-3-ol derivatives. Various phenylpropane glycerides were also found in the sorghum grain, the majority of them are reported here for the first time, and a few of them were detected with abundant peaks in the extracts, indicating they are another important class of phenolic compounds in sorghum. In addition, phenolamides were also found in sorghum grain, which have not been reported before, and dicaffeoyl spermidine was detected in high abundance in the extracts of all three type sorghum grains. These results confirmed that sorghum is a rich source of various phenolic compounds.

Phenolic compounds (hydroxycinnamic acids, flavan-3-ols, flavonols) profile in fruit of Italian peach varieties

Interest in phenolic compounds of fruit is growing due to their positive effects on reducing the risk of cardiovascular and carcinogen diseases. The role of the flesh colour, of the tissue (exocarp or mesocarp) and of the cultivar on the content of phenolic compounds (hydroxycinnamic acids, flavan-3-ols, flavonols) was evaluated in peach, Prunus persica (L.) Batsch, with a HPLC-DAD analysis, on 10 varieties deriving from the Italian breeding programmes, never previously characterized by this approach. The flavan-3-ols (catechin, epicatechin and procyanidin B1) were the most abundant class of phenolic compounds in peach cultivars analysed. Among hydroxycinnamic acids, neochlorogenic and chlorogenic acids were also identified and measured in the peach cultivars analysed. Quercetin-3-O-rutinoside was the only flavonol found in the exocarp of all the cultivars evaluated, but in the mesocarp of only some cultivars. Content of phenolic compounds was confirmed to be strongly dependent on the cultivar and, in general, the content was significantly higher in exocarp than in mesocarp. An overall significant difference in phenolic compounds as associated with flesh colour was not observed.

Antiatherogenic effects of ellagic acid and urolithins in vitro

Atherosclerosis, one of the leading causes of death worldwide, is characterized by impaired endothelial function and lipid metabolism, among other factors. Ellagitannins are a class of phenolic compounds that may play a role in cardiovascular health. This work aimed to study the potential atheroprotective effects of urolithins, ellagitannin-derived gut microbiota metabolites, on different key factors in atherosclerosis development: the ability of monocytes to adhere to endothelial cells and the uptake and efflux of cholesterol by macrophages. The biotransformations urolithins undergo in peripheral cells were also evaluated. Results indicated that some urolithins and ellagic acid were able to reduce the adhesion of THP-1 monocytes to human umbilical vein endothelial cells (HUVECs) and the secretion of a cellular adhesion molecule (sVCAM-1) and pro-inflammatory cytokine (IL-6). Urolithin C, a combination of urolithins A and B, and ellagic acid also decreased the accumulation of cholesterol in THP-1-derived macrophages, but they were not able to promote cholesterol efflux. The analysis of cell media by UHPLC-ESI-MSn indicated urolithins and ellagic underwent extensive metabolism, with sulfate and methyl conjugation. This evidence indicates that atherosclerotic processes may be attenuated by urolithins, but future human intervention trials are required to establish if is translated in vivo.

Bacterial synthesis of four hydroxycinnamic acids

Hydroxycinnamates are a class of phenolic compounds that have a C6-C3 carbon backbone. Hydroxycinnamic acids are derived from cinnamic acid via hydroxylation or methylation and are found in foods such as pears, coffee beans, and dandelions. They are involved in protection against chemotherapy side effects and the prevention of cardiovascular disease and cancer. We synthesized four types of hydroxycinnamates (p-coumaric acid, cinnamic acid, caffeic acid, and ferulic acid) from glucose in Escherichia coli by introducing different combination of four genes: tyrosine ammonia lyase, phenylalanine ammonia lyase, S.espanaensis monooxygenase, and Oryza sativa O-methyltransferase. The final yields of hydroxycinnamic acids were increased by engineering the metabolic pathway of E. coli. Using these strategies, 100.1 mg/L p-coumaric acid, 138.2 mg/L caffeic acid, 64 mg/L ferulic acid, and 1072.3 mg/L cinnamic acid were synthesized.

The in vitro propagation of Helichrysum umbraculigerum

Stilbenoids are a specific class of phenolic compounds, some of which show medicinal potential. Novel stilbenoids have previously been isolated from the South African plant Helichrysum umbraculigerum [1]. These prenylated resveratrol analogues are well known for their applications, which have mainly been discovered in research conducted on Cannabis sativa [2]. The applications include possible anti-inflammatory, antimicrobial and anticancer effects. H. umbraculigerum is known to be used by South African traditional healers. Exploitation of medicinal properties will require large numbers of plants, but H. umbraculigerum has proved difficult to cultivate. The aim of this study was to optimise an in vitro propagation protocol for H. umbraculigerum. Leaf cuttings were sterilised using 70% ethanol followed by 2% sodium hypochlorite containing 1 drop of Tween-20®. They were then washed in distilled water and placed onto Murashige and Skoog (MS) media. Uncontaminated leaf cuttings were placed onto MS media supplemented with different combinations of plant growth regulators. Shoots were produced most efficiently on MS media containing a specific concentration of thidiazuron (TDZ). These shoots were subsequently moved into the light, after which they started producing roots. Plantlets were successfully acclimatised using Jiffy-7C® pellets. The in vitro propagation protocol developed will allow for the production of large amounts of plant material for future research conducted on H. umbraculigerum.

Determination of Polar Compounds in Guava Leaves Infusions and Ultrasound Aqueous Extract by HPLC-ESI-MS

Literature lacks publications about polar compounds content in infusion or guava leaves tea. Because of that, a comparison between different times of infusion and a conventional ultrasound aqueous extract was carried out. Several polar compounds have been identified by HPLC-ESI-MS and their antioxidant activity was evaluated by FRAP and ABTS assays. Four different classes of phenolic compounds (gallic and ellagic acid derivatives, flavonols, flavanones, and flavan-3-ols) and some benzophenones were determined. The quantification results reported that the order, in terms of concentration of the classes of polar compounds in all samples, was flavonols &gt; flavan-3-ols &gt; gallic and ellagic acid derivatives &gt; benzophenones &gt; flavanones. As expected, the aqueous extract obtained by sonication showed the highest content in the compounds studied. Significative differences were noticed about the different times of infusion and five minutes was the optimal time to obtain the highest content in polar compounds using this culinary method. All the identified compounds, except HHDP isomers and naringenin, were positively correlated with antioxidant activity.

Composition of phenolics and volatiles in strawberry cultivars and influence of preharvest hexanal treatment on their profiles

Misran, A., Padmanabhan, P., Sullivan, J. A., Khanizadeh, S. and Paliyath, G. 2015. Composition of phenolics and volatiles in strawberry cultivars and influence of preharvest hexanal treatment on their profiles. Can. J. Plant Sci. 95: 115–126. Biochemical changes of quality-determining components were evaluated in strawberry fruit subjected to preharvest spray treatments using a hexanal-containing formulation that is known to enhance shelf life and quality of fruits. Phenolic compounds and volatiles of fruits of four strawberry cultivars (Mira, Jewel, Kent, and St. Pierre) grown in southern Ontario were characterized by HPLC-MS and solid phase micro extraction (SPME) analysis. Qualitative and quantitative profiles of phenolic compounds varied among the cultivars. In all the cultivars, anthocyanins constituted the most prominent class of phenolic compounds. Volatile profiles of strawberry homogenate differed among the cultivars. Changes in phenolics and volatiles composition were determined in fruits of Mira and Jewel after spraying with a hexanal-containing formulation at weekly intervals. In Jewel, preharvest hexanal spraying altered the profiles of polyphenolic components, while minimal changes were noticed in Mira. Interestingly, very few differences were identified in ester profiles of treated and untreated Mira. In general, hexanal spray application resulted in a decrease in the abundance of several volatile components including esters, ketones, and lactones in treated Jewel compared with the control. The results suggest that cultivar-specific quality changes may result from a preharvest application of hexanal formulations, which may also imply different patterns of metabolite channeling and delay of fruit ripening processes.

Health promoting and sensory properties of phenolic compounds in food

Phenolic compounds have been extensively studied in recent years. The presence of these compounds in various foods has been associated with sensory and health promoting properties. These products from the secondary metabolism of plants act as defense mechanisms against environmental stress and attack by other organisms. They are divided into different classes according to their chemical structures. The objective of this study was to describe the different classes of phenolic compounds, the main food sources and factors of variation, besides methods for the identification and quantification commonly used to analyze these compounds. Moreover, the role of phenolic compounds in scavenging oxidative stress and the techniques of in vitro antioxidant evaluation are discussed. In vivo studies to evaluate the biological effects of these compounds and their impact on chronic disease prevention are presented as well. Finally, it was discussed the role of these compounds on the sensory quality of foods.

Is guava phenolic metabolism influenced by elevated atmospheric CO2?

Seedlings of Psidium guajava cv. Pedro Sato were distributed into four open-top chambers: two with ambient CO2 (∼390 ppm) and two with elevated CO2 (∼780 ppm). Monthly, five individuals of each chamber were collected, separated into root, stem and leaves and immediately frozen in liquid nitrogen. Chemical parameters were analyzed to investigate how guava invests the surplus carbon. For all classes of phenolic compounds analyzed only tannins showed significant increase in plants at elevated CO2 after 90 days. There was no significant difference in dry biomass, but the leaves showed high accumulation of starch under elevated CO2. Results suggest that elevated CO2 seems to be favorable to seedlings of P. guajava, due to accumulation of starch and tannins, the latter being an important anti-herbivore substance.

Colloidal gas aphrons based separation process for the purification and fractionation of natural phenolic extracts

Following previous studies, the aim of this work is to further investigate the application of colloidal gas aphrons (CGA) to the recovery of polyphenols from a grape marc ethanolic extract with particular focus on exploring the use of a non-ionic food grade surfactant (Tween 20) as an alternative to the more toxic cationic surfactant CTAB. Different batch separation trials in a flotation column were carried out to evaluate the influence of surfactant type and concentration and processing parameters (such as pH, drainage time, CGA/extract volumetric and molar ratio) on the recovery of total and specific phenolic compounds. The possibility of achieving selective separation and concentration of different classes of phenolic compounds and non-phenolic compounds was also assessed, together with the influence of the process on the antioxidant capacity of the recovered compounds. The process led to good recovery, limited loss of antioxidant capacity, but low selectivity under the tested conditions. Results showed the possibility of using Tween 20 with a separation mechanism mainly driven by hydrophobic interactions. Volumetric ratio rather than the molar ratio was the key operating parameter in the recovery of polyphenols by CGA.

Update on transparent testa mutants from Arabidopsis thaliana: characterisation of new alleles from an isogenic collection.

We present a comprehensive overview on flavonoid-related phenotypes of A. thaliana tt and tds mutants, provide tools for their characterisation, increase the number of available alleles and demonstrate that tds3 is allelic to tt12 and tds5 to aha10. Flavonoid biosynthesis is one of the best-studied secondary metabolite pathways in plants. In the model system Arabidopsis thaliana it leads to the synthesis of three phenolic compound classes: flavonol glycosides, anthocyanins and proanthocyanidins (PAs). PAs appear brown in their oxidised polymeric forms, and most A. thaliana mutants impaired in flavonoid accumulation were identified through screens for lack of this seed coat pigmentation. These mutants are referred to as transparent testa (tt) or tannin-deficient seed (tds). More than 20 mutants of these types have been published, probably representing most of the genes relevant for PA accumulation in A. thaliana. However, data about the genes involved in PA deposition or oxidation are still rather scarce. Also, for some of the known mutants it is unclear if they represent additional loci or if they are allelic to known genes. For the present study, we have performed a systematic phenotypic characterisation of almost all available tt and tds mutants and built a collection of mutants in the genetic background of the accession Columbia to minimise effects arising from ecotype variation. We have identified a novel tt6 allele from a forward genetic screen and demonstrated that tds3 is allelic to tt12 and tds5 to aha10.