Comparison of colorimetric methods for the analysis of total polyphenols in green tea extracts.

Two colorimetric methods are used to determine the total polyphenol contents of tea, namely, "the Folin-Ciocalteu method," defined by the International Organization for Standardization, and the "iron tartrate method," specified in the Standard Tables of Food Composition in Japan. In this study, we compared the Folin-Ciocalteu and iron tartrate methods using green tea extracts. When comparing the 2 methods, the sum of the 4 major catechins measured using high-performance liquid chromatography (HPLC) was regarded as the standard value. The total polyphenol contents obtained using the Folin-Ciocalteu method were closer to the HPLC value than those obtained using the iron tartrate method. However, the iron tartrate method is adequate if the current official method is improved, that is, our results suggest that the coefficients appropriate for common green tea varieties, as well as the degree and duration of cover cultivation, in the official iron tartrate method must be considered.

Total urinary polyphenol excretion: a biomarker of an anti-inflammatory diet and metabolic syndrome status.

BACKGROUND: Chronic inflammation is associated with noncommunicable diseases, including obesity, metabolic syndrome (MetS), and CVDs. The Mediterranean diet has been shown to have strong anti-inflammatory effects, attributed in part to the polyphenol richness of many of its components. OBJECTIVES: This study aimed to assess the value of polyphenols as a urinary biomarker of an anti-inflammatory diet and their influence on MetS status. METHODS: A longitudinal analysis was performed in Spain considering 543 participants with high CVD risk in a PREDIMED study. Approximately 52% of the participants were women and 48% were men with a mean age of 67.5 (5.9) y. Total polyphenol excretion (TPE) in urine was determined at baseline and 5 y of intervention using a validated Folin-Ciocalteu spectrophotometric method, and the dietary inflammatory index (DII) was calculated from a validated 137-item food-frequency questionnaire. Three categories were built according to tertiles of change in the DII score. Multivariable linear regression analyses were performed to assess the association of changes in TPE with changes in the DII scores and with MetS status at 5 y. RESULTS: Tertiles 2 and 3 compared with tertile 1 presented a lower anti-inflammatory potential of the diet and were inversely associated with TPE in women [-0.30 mg gallic acid equivalent (GAE)/g creatinine; 95% CI: -0.46, -0.15; P value = 0.006 and -0.29 mg GAE/g creatinine; 95% CI: -0.43, -0.15; P value = 0.005], respectively. The mean changes in TPE were 7.9 (56.1) mg GAE/g creatinine in women and 7.7 (48.2) mg GAE/g creatinine in men. In addition, TPE was inversely associated with changes in MetS status [-0.06 (-0.09; -0.02), P value = 0.009] in both men and women. CONCLUSIONS: Urinary polyphenols may be a potential biomarker of anti-inflammatory diet consumption in women and are prospectively associated with improvement in MetS.

Edible Insects an Alternative Nutritional Source of Bioactive Compounds: A Review.

Edible insects have the potential to become one of the major future foods. In fact, they can be considered cheap, highly nutritious, and healthy food sources. International agencies, such as the Food and Agriculture Organization (FAO), have focused their attention on the consumption of edible insects, in particular, regarding their nutritional value and possible biological, toxicological, and allergenic risks, wishing the development of analytical methods to verify the authenticity, quality, and safety of insect-based products. Edible insects are rich in proteins, fats, fiber, vitamins, and minerals but also seem to contain large amounts of polyphenols able to have a key role in specific bioactivities. Therefore, this review is an overview of the potential of edible insects as a source of bioactive compounds, such as polyphenols, that can be a function of diet but also related to insect chemical defense. Currently, insect phenolic compounds have mostly been assayed for their antioxidant bioactivity; however, they also exert other activities, such as anti-inflammatory and anticancer activity, antityrosinase, antigenotoxic, and pancreatic lipase inhibitory activities.

Influence of Carbon Sources on the Phenolic Compound Production by Euglena gracilis Using an Untargeted Metabolomic Approach.

Industrial development and urbanization has led to the diverse presence of metals in wastewater that are often improperly treated. The microalgae Euglena gracilis can tolerate high concentrations of metal via the excretion of organic metabolites, including phenolics. This study aims to evaluate how carbon amendment stimulates phenolic compound production by E. gracilis. The number, relative intensity and molecular composition of the phenolic compounds were significantly different between each of four carbon amended cultures (i.e., glutamic acid, malic acid, glucose, reduced glutathione) during the log phase. Phenolic compounds were mainly produced during the minimum growth rate, likely a response to stressful conditions. A better understanding of phenolic compounds production by E. gracilis and the impact of growth conditions will help identify conditions that favor certain phenolic compounds for dietary and metal chelation applications.

Implementation of an Analytical Method for Spectrophotometric Evaluation of Total Phenolic Content in Essential Oils.

Over the past decade, there has been growing interest in polyphenols' research since these compounds, as antioxidants, have several health benefits, such as preventing neurodegenerative diseases, inflammation, cancer, cardiovascular diseases, and type 2 diabetes. This study implements an analytical method to assess the total phenolic content (TPC) in essential oils using Folin-Ciocalteu's phenol reagent and quantifies the individual phenolic compounds by liquid chromatography. Thus, the research design and methodology included: (1) extraction of essential oil from dried thyme leaves by hydrodistillation; (2) spectrophotometric measurement of TPC by Folin-Ciocalteu method; and (3) identification and quantification of individual phenolic compounds by high-performance liquid chromatography-diode array detection/electrospray ionization mass spectrometry (HPLC-DAD-ESI-MS). Results revealed a TPC of 22.62 ± 0.482 mg GAE/100 µL and a polyphenolic profile characterized by phenolic acids (52.1%), flavonoids (16.1%), and other polyphenols (31.8%). Thymol, salvianolic acid A, and rosmarinic acid were the major compounds of thyme essential oil. The proposed analytical procedure has an acceptable level of repeatability, reproducibility, linearity, LOD (limit of detection), and LOQ (limit of quantification).

A validated Folin-Ciocalteu method for total phenolics quantification of condensed tannin-rich açaí (Euterpe oleracea Mart.) seeds extract.

ABSTRACT: The widely used methodology to quantify polyphenols-the Folin-Ciocalteu (FC) method-cannot be applied indiscriminately since different matrices may impair the assay's accuracy. Thus, this study aimed to adapt the FC method for the açaí seed extract, a tannin-rich extract with potential applications for various therapies. Firstly, a pre-method standardization was established to determine parameters such as reading wavelength (765 nm), reaction time (30 min), and the reference substance (pyrogallol). In the validation step, the adapted method responded linearly to the analyte (R2 = 0.9910), ensuring its selectivity (linearity and selectivity curves statistically parallel) and accuracy (99.18-101.43%). Furthermore, the method proved to be precise (RSD ≤ 2.63%) at the two levels assessed (repeatability and intermediate precision) and robust (RSD ≤ 4.45%) concerning variation on the Na2CO3 concentration and the reaction time. The limits of detection and quantification were also calculated (9.9 µg/mL and 33.1 µg/mL, respectively). An additional step for tannins quantification based on its reported selective precipitation by complexing agents was also evaluated; however, unspecific precipitation was observed, reducing the results' accuracy. Our work successfully adapted and validated a method for total phenolics quantification of açaí seed extract, resulting in 38 g of pyrogallol equivalent/100 g of extract.

Determination of selenium species in beetroot juices.

Over the past years, there is an increasing demand for healthy, natural foods. Due to the high content of betalains, beetroots are widely used in the food industry as a natural colorant. In this study, beetroot juices are shown as a great source of selenium compounds. The juices were purchased from a local store and the ecological one was purchased form organic street market. The content of organic selenium species, as well as betalains, were evaluated using hydrophilic interaction liquid chromatography (HILIC) chromatography. The concentrations of selenomethionine (SeMet) and methylselenocysteine (MeSeCys) in analyzed juices were comparable except for juice from ecological cultivation. In that case, the concentration of SeMet is the highest of all studied juices, but simultaneously the concentration of MeSeCys was the lowest one. No traces of major inorganic species of Se, such as Se(IV) and Se(VI) was detected. The reducing power of juices evaluated by Folin-Ciocalteu assay was in range 50.78-166.7 mg GA/L. Juices obtained from beetroot from ecological cultivation showed the highest ability to scavenge the 1,1-diphenyl-2- picrylhydrazyl (DPPH) radicals. There was a correlation between the yellow pigment content and the presence of selenocysteine in studied juices.

Quality assessment of fresh tea leaves by estimating total polyphenols using near infrared spectroscopy.

This paper reports on the development of an integrated leaf quality inspecting system using near infrared reflectance (NIR) spectroscopy for quick and in situ estimation of total polyphenol (TP) content of fresh tea leaves, which is the most important quality indicator of tea. The integrated system consists of a heating system to dry the fresh tea leaves to the level of 3-4% moisture, a grinding and sieving system fitted with a 250 micron mesh sieve to make fine powder from the dried leaf. Samples thus prepared are transferred to the NIR beam and TP is measured instantaneously. The wavelength region, the number of partial least squares (PLS) component and the choice of preprocessing methods are optimized simultaneously by leave-one-sample out cross-validation during the model calibration. In order to measure polyphenol percentage in situ, the regression model is developed using PLS regression algorithm on NIR spectra of fifty-five samples. The efficacy of the model developed is evaluated by the root mean square error of cross-validation, root mean square error of prediction and correlation coefficient (R2) which are obtained as 0.1722, 0.5162 and 0.95, respectively.

Microwave-assisted extraction in dry fruit of andean species Vaccinium meridionale: Experimental conditions on the recovery of total polyphenols / Extração assistida por microondas para frutos da espécie andina Vaccinium meridionale: Condições experimentais na remoção de polifenóis totais

ABSTRACT Due to their nutraceutical properties, the fruits of the species Vaccinium meridionale, which inhabit the Andean region, are of scientific interest. Microwave-assisted extraction has been applied to different vegetal matrices for to extract efficiently polyphenolic compounds. In this work we study in microwave assisted extraction processes, the effect on the extraction of total polyphenols in dried fruits of Vaccinium meridionale, using response surface methodology. The main objective of this research was to analyze the relationships between power, temperature, solid-liquid ratio, time and ethanol concentration in aqueous media on the effectiveness of total polyphenols recovery in dry fruits of Vaccinium meridionale. A central composite design face-centered with three levels for each variable was used: P = 300 - 900 W; T = 70 -110 °C; L:Srat. = 30:1 - 70:1 w/w; t = 5 - 15 min; [EtOH] = 0 - 80%. In this sense, the effect of the input variables on the recovery of total polyphenols, the optimization process for maximum extraction, and the comparison to other solid-liquid extractions in terms of quantity of total polyphenols, are reported. It was found that the significant variables in the extraction process were ethanol concentration, temperature and time; the best yields were obtained in the range [EtOH] = 44 - 49%, T = 110 °C, and t = 10 - 15 min. In terms of quantity, time and consumption of energy, microwave-assisted extraction technique is more efficient than other solid-liquid extraction processes for the extraction of total polyphenols.

RESUMO Devido a suas propriedades nutracêuticas em termos do conteúdo de polifenóis totais, os frutos da espécie andina Vaccinium meridionale tem associado um grande interesse cientifico. A extração assistida por microondas tem sido utilizada em diferentes matrizes vegetais para a remoção de forma eficiente de compostos polifenólicos que apresentam uma atividade biológica. Neste artigo são apresentados os principais resultados experimentais obtidos em diferentes processos de extração assistida por microondas, com respeito à quantia de polifenóis totais removidos em frutos secos de Vaccinium meridionale por meio da metodologia da superfície de resposta. O principal objetivo desta pesquisa foi analisar as relações entre as variáveis independentes da potência, a temperatura, a relação sólido-líquido, tempo e concentração de etanol com respeito à quantidade polifenóis totais extraídos de frutos secos de Vaccinium meridionale. Foi utilizado um desenho composto centrado nas caras com três diferentes níveis para cada variável: P = 300 - 900 W; T = 70 -110 °C; L:Srat. = 30:1 - 70:1 w/w; t = 5 - 15 min; [EtOH] = 0 - 80%. Foi utilizado o método de Folin-Ciocalteu para a quantificação de polifenóis totais com ácido gálico como molécula de referência. Neste sentido, foi reportado neste trabalho o efeito dos fatores de entrada com respeito a quantidade de polifenóis totais removidos, o processo de optimização para obter a máxima remoção possível, e também uma comparação dos resultados experimentais com outros processos de extração sólido-líquido. Foi achado que a concentração de etanol, a temperatura e o tempo foram a variáveis mais importantes no processo de extração. A máxima quantidade de recuperação achada neste trabalho foi obtida no intervalo [EtOH] = 44 - 49%, T = 110 °C e t = 10 - 15 min. Em termos de quantidade, tempo e gasto de energia, a extração assistida por microondas é uma técnica eficiente para a remoção de polifenóis totais em frutos secos de Vaccinium meridionale.

Optimization and validation of Folin-Ciocalteu method for the determination of total polyphenol content of Pu-erh tea.

Pu-erh tea is a post-fermented tea that has recently gained popularity worldwide, due to potential health benefits related to the antioxidant activity resulting from its high polyphenolic content. The Folin-Ciocalteu method is a simple, rapid, and inexpensive assay widely applied for the determination of total polyphenol content. Over the past years, it has been subjected to many modifications, often without any systematic optimization or validation. In our study, we sought to optimize the Folin-Ciocalteu method, evaluate quality parameters including linearity, precision and stability, and then apply the optimized model to determine the total polyphenol content of 57 Chinese teas, including green tea, aged and ripened Pu-erh tea. Our optimized Folin-Ciocalteu method reduced analysis time, allowed for the analysis of a large number of samples, to discriminate among the different teas, and to assess the effect of the post-fermentation process on polyphenol content.

Comparison of Protein Content Determination Respectively by Folin-Ciocalteu Method and Coomassie Bril-liant Blue Binding Method for Mannatide Oral Solution / 中国药师

Objective:To establish the protein content determination method respectively by Folin-Ciocalteu method and Coomass-ie brilliant blue binding method for mannatide oral solution and compare the results. Methods:The limit of detection, linearity, accu-racy, repeatability, recovery and content of Folin-Ciocalteu method and Coomassie brilliant blue binding method were investigated. Re-sults:As for Folin-Ciocalteu method, the limit of detection was 0. 2 μg, the range of linearity was 0-112. 0 μg(r=0. 9990), the av-erage recovery was 105. 2%(RSD=1. 9%), the RSD of accuracy was less than 1%, and the content result of three batches of samples was 47. 45, 58. 34 and 40. 99 μg·ml-1, respectively. As for Coomassie brilliant blue binding method, the limit of detection was 0. 8 μg, the range of linearity was 0-99. 6 μg(r=0. 9980), the average recovery was 102. 0%(RSD=2. 7%), the RSD of accuracy was less than 1%, and the protein content of samples was not detected out by the method. Conclusion:Folin-Ciocalteu method can be used to determine the protein content in mannatide oral solution reliably and efficiently.

Comparison of Protein Content Determination Respectively by Folin-Ciocalteu Method and Coomassie Bril-liant Blue Binding Method for Mannatide Oral Solution / 中国药师

Objective:To establish the protein content determination method respectively by Folin-Ciocalteu method and Coomass-ie brilliant blue binding method for mannatide oral solution and compare the results. Methods:The limit of detection, linearity, accu-racy, repeatability, recovery and content of Folin-Ciocalteu method and Coomassie brilliant blue binding method were investigated. Re-sults:As for Folin-Ciocalteu method, the limit of detection was 0. 2 μg, the range of linearity was 0-112. 0 μg(r=0. 9990), the av-erage recovery was 105. 2%(RSD=1. 9%), the RSD of accuracy was less than 1%, and the content result of three batches of samples was 47. 45, 58. 34 and 40. 99 μg·ml-1, respectively. As for Coomassie brilliant blue binding method, the limit of detection was 0. 8 μg, the range of linearity was 0-99. 6 μg(r=0. 9980), the average recovery was 102. 0%(RSD=2. 7%), the RSD of accuracy was less than 1%, and the protein content of samples was not detected out by the method. Conclusion:Folin-Ciocalteu method can be used to determine the protein content in mannatide oral solution reliably and efficiently.

Determination of total antioxidant capacity of humic acids using CUPRAC, Folin-Ciocalteu, noble metal nanoparticle- and solid-liquid extraction-based methods.

Total antioxidant capacity (TAC) of humic acid (HA) samples was determined using CUPRAC (CUPric Reducing Antioxidant Capacity), FC (Folin-Ciocalteu), QUENCHER-CUPRAC, QUENCHER-FC, Ag-NP (Silver nanoparticle)‒ and Au-NP (Gold nanoparticle)‒based methods. Conventional FC and modified FC (MFC) methods were applied to solid samples. Because of decreased solubility of Folin-Ciocalteu's phenol reagent in organic solvents, solvent effect on TAC measurement was investigated using QUENCHER-CUPRAC assay by using ethanol:distilled water and dimethyl sulfoxide:distilled water with varying ratios. To see the combined effect of solubilization (leaching) and TAC measurement of humic acids simultaneously, QUENCHER experiments were performed at 25°C and 50°C; QUENCHER-CUPRAC and QUENCHER-FC methods agreed well and had similar precision in F-statistics. Although the Gibbs free energy change (ΔG°) of the oxidation of HA dihydroxy phenols with the test reagents were negative, the ΔG° was positive only for the reaction of CUPRAC reagent with isolated monohydric phenols, showing CUPRAC selectivity toward polyphenolic antioxidants. This is the first work on the antioxidant capacity measurement of HA having a sparingly soluble matrix where enhanced solubilization of bound phenolics is achieved with coupled oxidation by TAC reagents.

Content Variation of Catechin Markers, Total Phenolics and Caffeine in Green Tea Dietary Supplements.

Green tea (Camellia sinensis) preparations are among the top selling products in the United States dietary supplements market. Numerous manufacturers claim different levels of specific catechin markers in their products while many others use total phenolic concentration instead, or not at all. Limited quality control results have been published for green tea dietary supplements over the past seven years. Thus, the goal of this work was to correlate determined levels of phenolics, catechins, and caffeine with manufacturer label claims for selected dietary supplement products (26 total) purchased in the United States. The Folin-Ciocalteu (FC) method was used to determine the total phenolic content while reversed-phase (RP) HPLC was used to quantify the major catechins: epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), epigallocatechin gallate (EGCG). The developed HPLC method was validated for accuracy and precision. It utilized a C8 column with gradient elution of acetonitrile in 0.1% aqueous formic acid over 11 min total run time. Peak detection was performed at 280 nm. Caffeine was also included in the HPLC method as another non-phenolic alkaloid marker commonly found in green tea. Both methods showed a good correlation between the content of catechins and polyphenolic compounds in the selected products. The ranges of total catechins and polyphenol concentrations were 3.8-70.2% and 3.6-95.8%, respectively, while that of caffeine was 0.8-11.2%. The selected products displayed a wide range of marker levels. A lack of conformity in disclosing the actual levels of marker compounds was also noticed in the labeling of many products.