Determination Of Total Polyphenols Research Articles

Analysis of physical, mechanical and chemical properties of seeds and kernels of Jatropha curcas

The research was performed to examine the physical, mechanical and chemical properties of seeds and kernels of Jatropha curcas. The test parameters were the dimensions of the seeds and kernels, required energy for oil extraction, determination of fatty acids in the oil by gas chromatography method, determination of the iodine value, determination of the acid value, determination of total polyphenols by the Folin & Ciocault reagent and determination of tocopherols and tocotrienols (vitamin E) by High-performance liquid chromatography. It was ascertained that the size of the seed and kernel varies considerably. Pressing of whole seeds needs more energy (50%) than pressing of kernels. From a chemical point of view it seems to be very appropriate for a production of biofuels. Jatropha curcas contains more polyphenols and vitamin E, which act as antioxidants, than the rape. Due to the low content of unsaturated fatty acids it is chemically suitable to replace the rape-seed oil with Jatropha curcas oil.

Raw Juice Concentration by Osmotic Membrane Distillation Process with Hydrophobic Polymeric Membranes

Hydrophobic polymeric membranes (PP, PTFE, and PVDF) were efficiently applied in juice concentration by osmotic membrane distillation process at room temperature. The properties of applied membranes were characterized by the value of static contact angle, hysteresis of contact angle, surface free energy, roughness, mean flow pore size, maximum pore size or bubble point, and the pore size distribution before and after their utilization in osmotic membrane distillation (OMD). Furthermore, the mechanical strength of the membranes was evaluated using the Mullen burst technique and characterization of fouling behavior was done. The impact of stripping solutions, characterized by different water activities (NaCl and CaCl2), type of membrane materials, and membrane morphology, on the transport properties in a dehydration process was evaluated. Apple and beet juices with a high level of antioxidants were chosen. The quality of juices has been assessed by determination of total polyphenols and antioxidant activity. In the dehydration process, the most efficient were 0.45-μm PTFE and 0.45-μm PVDF membranes (24 % improvement). No loss of polyphenol content or reduction of antioxidant activity was observed after the juice dehydration.

Gold Nanoparticles-based Extraction-Free Colorimetric Assay in Organic Media: An Optical Index for Determination of Total Polyphenols in Fat-Rich Samples.

In this work, a rapid and simple gold nanoparticle (AuNPs)-based colorimetric assay meets a new type of synthesis of AuNPs in organic medium requiring no sample extraction. The AuNPs synthesis extraction-free approach strategically involves the use of dimethyl sulfoxide (DMSO) acting as an organic solvent for simultaneous sample analyte solubilization and AuNPs stabilization. Moreover, DMSO works as a cryogenic protector avoiding solidification at the temperatures used to block the synthesis. In addition, the chemical function as AuNPs stabilizers of the sample endogenous fatty acids is also exploited, avoiding the use of common surfactant AuNPs stabilizers, which, in an organic/aqueous medium, rise to the formation of undesirable emulsions. This is controlled by adding a fat analyte free sample (sample blank). The method was exhaustively applied for the determination of total polyphenols in two selected kinds of fat-rich liquid and solid samples with high antioxidant activity and economic impact: olive oil (n = 28) and chocolate (n = 16) samples. Fatty sample absorbance is easily followed by the absorption band of localized surface plasmon resonance (LSPR) at 540 nm and quantitation is refereed to gallic acid equivalents. A rigorous evaluation of the method was performed by comparison with the well and traditionally established Folin-Ciocalteu (FC) method, obtaining an excellent correlation for olive oil samples (R = 0.990, n = 28) and for chocolate samples (R = 0.905, n = 16). Additionally, it was also found that the proposed approach was selective (vs other endogenous sample tocopherols and pigments), fast (15-20 min), cheap and simple (does not require expensive/complex equipment), with a very limited amount of sample (30 μL) needed and a significant lower solvent consumption (250 μL in 500 μL total reaction volume) compared to classical methods.

Study on drying methods and their influences on effective components of loquat flower tea

Different drying methods and their influences on effective components contents of loquat flower tea were investigated in this study. The determination of total polyphenols (TP), total flavonoids (TF), free amino acid (AA), caffeine and triterpene acids showed relatively higher contents were found at full-bloom stage and in petal tissue. This stage flower was dried to produce loquat flower tea by methods of freeze drying, microwave drying, vacuum drying and hot-air drying, respectively. The results showed that four water-soluble components contents in tea prepared by freeze drying were the highest. Those by microwave drying increased firstly, then decreased with power, with the maximum at 420 W. In vacuum-dried tea, total polyphenols content (TPC) and total flavonoids content (TFC) reduced with temperature, but for AA, it increased with temperature. In hot-air dried flower tea, TPC and TFC exhibited a similar tendency as those by microwave dry, with the maximum at 80 °C and minimum at 40 °C. For AA, it increased with temperature. The contents of caffeine, triterpene acid in tea prepared by all drying methods showed no significant difference. It was concluded that the methods of freeze drying and microwave drying at 420 W can protect the effective components preferably.

Using iSPA-PLS and NIR spectroscopy for the determination of total polyphenols and moisture in commercial tea samples

The determination of total polyphenols and moisture in commercial tea samples using iSPA-PLS and NIR spectroscopy.

Potentiometric Determination of Total Polyphenols in Green Tea Based on Complexation-Reaction-Induced Response

Potentiometric Determination of Total Polyphenols in Green Tea Based on Complexation-Reaction-Induced Response

Optimization of solvent mixtures for extraction from bark of Schinus terebinthifolius by a statistical mixture-design technique and development of a UV-Vis spectrophotometric method for analysis of total polyphenols in the extract

A statistical mixture-design technique was used to study the effects of different solvents and their mixtures on the yield, total polyphenol content, and antioxidant capacity of the crude extracts from the bark of Schinus terebinthifolius Raddi (Anacardiaceae). The experimental results and their response-surface models showed that ternary mixtures with equal portions of all the three solvents (water, ethanol and acetone) were better than the binary mixtures in generating crude extracts with the highest yield (22.04 ± 0.48%), total polyphenol content (29.39 ± 0.39%), and antioxidant capacity (6.38 ± 0.21). An analytical method was developed and validated for the determination of total polyphenols in the extracts. Optimal conditions for the various parameters in this analytical method, namely, the time for the chromophoric reaction to stabilize, wavelength of the absorption maxima to be monitored, the reference standard and the concentration of sodium carbonate were determined to be 5 min, 780 nm, pyrogallol, and 14.06% w v-1, respectively. UV-Vis spectrophotometric monitoring of the reaction under these conditions proved the method to be linear, specific, precise, accurate, reproducible, robust, and easy to perform.

Determination of Total Polyphenols and Nutritional Composition of Two Different Types of Ficus carica Leaves Cultivated in Saudi Arabia

Ficus carica grows in tropical and subtropical regions of Saudi Arabia. The current study was conducted to evaluate the proximate analyses, minerals, alpha-tocopherol and vitamin C contents, and to investigate the antioxidant capacities of aqueous and methanolic extracts prepared from Ficus carica leaves. The antioxidant capacities in the forms of DPPH and FRAP were evaluated by spectrophotometric methods. Alpha-tocopherol and vitamin C contents were determined by using a high-performance liquid chromatography (HPLC)-UV method. Total phenolic content was determined by using the Folin-Ciocalteau method. The results indicated that TPC, DPPH and FRAP values were higher in methanolic extract of big Ficus carica leaf (412.37±57.9mg GAE/100 g, 63.29±2.51% and 131.39±13.96 mmol Fe /100 g) i n 2+ comparison to small leaf. Total phenolics were however higher in aqueous extract compared to methanolic. The results clearly demonstrate that these extracts have antioxidant capacity though there was no significant correlation between total phenolic content and antioxidant activity. Also, nutritional composition of Ficus carica leaves showed that they are good sources of minerals. Ficus carica leaf is therefore a rich source of polyphenols and has high antioxidant properties.

Evaluation of the Chemiluminometric Method for Determination of Polyphenols in Wine

The Pholasin chemiluminometric method for determination of polyphenols in wine was evaluated by comparison with liquid chromatography with mass-spectrometric detection. The results were also compared with the conventional Singleton-Rossi spectrophotometric method for determination of total polyphenols. A total of 141 wine samples were examined using all three methods and the results indicated a good agreement between the chemiluminometric and the Singleton-Rossi methods; however, the chromatographic data correlated reasonably well with the chemiluminometric data only for gallic acid, but less well or not at all with other determined phenolic antioxidants: trans-resveratrol, (+)-catechin, (−)-epicatechin, quercetin, vanillic-, caffeic-, caftaric-, p-coumaric-, 3,4-dihydroxybenzoic-, ellagic-, sinapic-, ferullic-, and ellagic acid.

Total polyphenols from Syzygium cumini (L.) Skeels fruit extract

A precise, accurate and low cost spectrophotometric method was developed and validated for routine determination of total polyphenols, as pyrogallic acid equivalents, from the percolated and lyophilized extract of Syzygium cumini (L.) Skeels fruits. Validation was assessed experimentally and data were rigorously treated by statistical analysis. Analytical parameters were: linearity, interval (range), precision and recovery/accuracy, limit of detection (LOD, μg mL-1) and limit of quantification (LOQ, μg mL-1). The visible spectrophotometric method presented linearity (r² = 0.9979 ± 0.0010) over the concentration range 0.25-7.5 μg mL-1 of standard pyrogallic acid, precision < 2.918171%, recovery/accuracy ranging from 96.228693 to 107.17701%, LOD = 0.21 μg mL-1 and LOQ = 0.64 μg mL-1.

Flow Injection Analysis-Spectrophotometry for Rapid Determination of Total Polyphenols in Tea Extracts

A simple flow injection analysis-spectrophotometric system for the rapid determination of total polyphenols (TP) in tea extracts was developed. The method is based on Folin-Ciocalteu (FC) reaction, which involves the oxidation/reduction of polyphenolic compounds by FC reagent in alkaline medium, producing a blue molybdenum-tungsten complex. The linear range of the calibration graph was 10 – 500 mg gallic acid equivalent (GAE)/l. The relative standard deviation (RSD) (n=5) of the calibration graph was 2.93%. The precisions (%RSD, n=10) of the determination at low and high concentrations were 2.74% for the 10 mg GAE/l and 3.02% for the 500 mg GAE/l, respectively. The detection limit was 7 mg/l. The sample throughput was 30 per hour. The TP contents in tea extracts determined by the developed system were compared with those determined by the standard batch method and no significant difference was found (t test, at 95% confidence level).

Simultaneous determination of total polyphenols and caffeine contents of green tea by near-infrared reflectance spectroscopy

This paper indicates the possibility to use near infrared (NIR) spectroscopy as a rapid method to predict quantitatively the content of caffeine and total polyphenols in green tea. A partial least squares (PLS) algorithm is used to perform the calibration. To decide upon the number of PLS factors included in the PLS model, the model is chosen according to the lowest root mean square error of cross-validation (RMSECV) in training. The correlation coefficient R between the NIR predicted and the reference results for the test set is used as an evaluation parameter for the models. The result showed that the correlation coefficients of the prediction models were R = 0.9688 for the caffeine and R = 0.9299 for total polyphenols. The study demonstrates that NIR spectroscopy technology with multivariate calibration analysis can be successfully applied as a rapid method to determine the valid ingredients of tea to control industrial processes.

Spectrophotometric methods to differentiate beers and evaluate beer ageing

The methodology most widely used to detect the antioxidant capacity (indirectly by ABTS + discoloration) has been modified to be applied to beer samples due to signal instabilities. A new and direct method to follow beer ageing has been developed based on a simple organic solvent extraction follow by molecular absorption spectrophotometry UV–VIS (MAS) measurement. Polyphenols and Maillard reaction products (MRPs) implied in beer ageing have been identified in the organic extract. A wide sampling of beers has been performed considering different countries, raw materials and brewing process. The two methods mentioned have been applied to the samples as well as the determination of total polyphenols, iron, copper and manganese by its role in ageing and in fermentation. In all cases, the data were obtained by triplicates. High correlation coefficients have been obtained between the ABTS + and the extraction method, therefore, this second method is proposed to differentiate antioxidant capacity and to follow beer ageing. The analysis of variance (ANOVA) has shown the possibility to differentiate types of beers and ecological from non-ecological beers.

Spectrophotometric method for polyphenols analysis: Prevalidation and application on Plantago L. species

The prevalidation strategy was applied to evaluate UV–vis spectrophotometric procedure with Folin–Ciocalteu's reagent for polyphenols determination. Favourable prevalidation characteristics verified this procedure as a valuable tool in polyphenols analysis and it was successfully applied for determination of total polyphenols and tannins in leaves, stems and flowers of Plantago L. species growing in Croatia. The results showed the variety of total polyphenols content between different plant parts (leaves: up to 10.15%; stems: up to 4.34% and flowers: up to 5.56%). The content of tannins in stems was from 0.28% to 1.00%, while leaves and flowers contained tannins in concentrations of 2.26% and 2.21%, respectively. The results of polyphenols determination were evaluated by using multivariate analysis (UPGMA and PCA) as a contribution to elucidation of relations between different taxa of genus Plantago L.

Phenolic compounds profile of cornicabra virgin olive oil.

This study presents the phenolic compounds profile of commercial Cornicabra virgin olive oils from five successive crop seasons (1995/1996 to 1999/2000; n = 97), determined by solid phase extraction reversed phase high-performance liquid chromatography (SPE RP-HPLC), and its relationship with oxidative stability, processing conditions, and a preliminary study on variety classification. The median of total phenols content was 38 ppm (as syringic acid), although a wide range was observed, from 11 to 76 ppm. The main phenols found were the dialdehydic form of elenolic acid linked to tyrosol (p-HPEA-EDA; 9 +/- 7 ppm, as median and interquartile range), oleuropein aglycon (8 +/- 6 ppm), and the dialdehydic form of elenolic acid linked to hydroxytyrosol (3,4-DHPEA-EDA; 5 +/- 8 ppm). In many cases the correlation with oxidative stability was higher when the sum of the dialdehydic form of elenolic acid linked to hydroxytyrosol (3,4-DHPEA-EDA) and oleuropein aglycon (r (2) = 0.91-0.96) or the sum of these two and hydroxytyrosol (r (2) = 0.90-0.97) was considered than was observed with HPLC total phenols (r (2)= 0.91-0.95) and especially with colorimetric determination of total polyphenols and o-diphenols (r (2) = 0.77-0.95 and 0.78-0.92, respectively). 3,4-DHPEA-EDA, p-HPEA-EDA, the aglycons of oleuropein and ligstroside, and HPLC total phenols content presented highly significant differences (p = 0.001-0.010) with respect to the dual- and triple-phase extraction systems used, whereas colorimetric total polyphenols content did not (p = 0.348) and o-diphenols showed a much lower significant difference (p = 0.031). The five variables that most satisfactorily classified the principal commercial Spanish virgin olive oil varieties were 1-acetoxypinoresinol, 4-(acetoxyethyl)-1,2-dihydroxybenzene (3,4-DHPEA-AC), ligstroside aglycon, p-HPEA-EDA, and RT 43.3 contents.

SCREENING OF POLYPHENOLS IN GRAPE MARC BY ON-LINE SUPERCRITICAL FLUID EXTRACTION–FLOW THROUGH SENSOR

An on-line supercritical fluid extraction continuous flow manifold including a flow through sensor was used and applied to the quantitative determination of total polyphenols in grape marc samples. A clean, highly selective supercritical fluid extraction (SFE) method for the isolation of phenols from grape marc samples was optimised. Dried, ground, and sieved grape marc (0.1 g) were subjected to SFE with CO2 modified with 5% methanol at 350 bar and 50°C(CO2 density 0.9 g ml(−1) for 15 min at a liquid flow-rate of 4 ml min−1. Diatomaceous earth was used to reduce the void volume of the extraction vessel. The analytes were concentrated on a PorapackQ or ODS trap and subsequently eluted with methanol. The influence of extraction variables such as modifier content, pressure, temperature, flow-rate, extraction time, and collection/elution variables, were studied. Total phenol extracts were determined by using a direct measurement at 270 nm as screening method.

Coupled robot-flow injection analysis system for fully automated determination of total polyphenols in olive oil

Coupled robot-flow injection analysis system for fully automated determination of total polyphenols in olive oil

Stabilization of the Prussian blue color in the determination of polyphenols

A stabilized reagent for the determination of total polyphenols by the Prussian blue method was developed. H3PO4 complexed with excess Fe3+ in the mixture, stopping the reaction. Gum acacia, a protective colloid, prevented precipitation by impeding the coalescence of the colloidal particles formed. Efficiency of chelating agents tried was H3PO4 (A) Na4EDTA (B) sodium hexametaphosphate (C). Effectiveness of protective colloids was gum acacia (D) = Reten (an anionic polyacrylamide) (E) Methocel 60 HG (F) phosphomannan 2448 (G) starch (H) polysaccharide B 1828 (I). Both the chelating agent and the protective colloid must be added to effect stabilization. Effectiveness of combinations was (A + D or E) (B + D) (A + F) (A + G) all other combinations. (A + D) prevented change in color density and prevented precipitation for up to 60 h with catechin as the polyphenol

Determination of total polyphenols in beers by flow injection analysis

Two automatic flow injection methods for the determination of total polyphenols in beers based on classical reactions (the Folin-Ciocalteu reagent method and the International Official method) are proposed. Their usefulness was tested by applying them to different beers. The results obtained agree with those provided by the corresponding batch methods.

A METHOD FOR ESTIMATING TOTAL POLYPHENOLS IN BEER

A procedure is described whereby polyphenols in beer are extracted under acid and alkaline conditions. These fractions are analysed to obtain the net amount of polyphenols and these are in turn used as standards for calibration in developing a colorimetric method for the determination of total polyphenols in beer.