Publisher Summary This chapter discusses the analysis of total phenols and other oxidation substrates and antioxidants by means of Folin-Ciocalteu reagent. Analyses of the Folin-Ciocalteu (FC) type are convenient, simple, and require only common equipment and have produced a large body of comparable data. Under proper conditions, the assay is inclusive of monophenols and gives predictable reactions with the types of phenols found in nature. Because different phenols react to different degrees, expression of the results as a single number—such as milligrams per liter gallic acid equivalence—is necessarily arbitrary. Because the reaction is independent, quantitative, and predictable, analysis of a mixture of phenols can be recalculated in terms of any other standard. The assay measures all compounds readily oxidizable under the reaction conditions and its very inclusiveness allows certain substances to also react that are either not phenols or seldom thought of as phenols (e.g., proteins). Judicious use of the assay—with consideration of potential interferences in particular samples and prior study if necessary—can lead to very informative results. Aggregate analysis of this type is an important supplement to and often more informative than reems of data difficult to summarize from various techniques, such as high-performance liquid chromatography (HPLC) that separate a large number of individual compounds .The predictable reaction of components in a mixture makes it possible to determine a single reactant by other means and to calculate its contribution to the total FC phenol content. Relative insensitivity of the FC analysis to many adsorbents and precipitants makes differential assay—before and after several different treatments—informative.

Analysis of total phenols and other oxidation substrates and antioxidants by means of folin-ciocalteu reagent

Physiological and ecological constraints play key roles in the evolution of plant growth patterns, especially in relation to defenses against herbivores. Phenotypic and life history theories are unified within the growth-differentiation balance (GDB) framework, forming an integrated system of theories explaining and predicting patterns of plant defense and competitive interactions in ecological and evolutionary time. Plant activity at the cellular level can be classified as growth (cell division and enlargement) of differentiation (chemical and morphological changes leading to cell maturation and specialization). The GDB hypothesis of plant defense is premised upon a physiological trade-off between growth and differentiation processes. The trade-off between growth and defense exists because secondary metabolism and structural reinforcement are physiologically constrained in dividing and enlarging cells, and because they divert resources from the production of new leaf area. Hence the dilemma of plants: Th...

https://www.jstor.org/stable/pdfplus/2830650.pdf

The dilemma of plants: To grow or defend.

A method for the quantitative recovery of protein in dilute solution in the presence of detergents and lipids

Polyphenols constitute one of the most numerous and ubiquitous groups of plant metabolites and are an integral part of both human and animal diets. Ranging from simple phenolic molecules to highly polymerized compounds with molecular weights of greater than 30,000 Da, the occurrence of this complex group of substances in plant foods is extremely variable. Polyphenols traditionally have been considered antinutrients by animal nutritionists, because of the adverse effect of tannins, one type of polyphenol, on protein digestibility. However, recent interest in food phenolics has increased greatly, owing to their antioxidant capacity (free radical scavenging and metal chelating activities) and their possible beneficial implications in human health, such as in the treatment and prevention of cancer, cardiovascular disease, and other pathologies. Much of the literature refers to a single group of plant phenolics, the flavonoids. This review offers an overview of the nutritional effects of the main groups of polyphenolic compounds, including their metabolism, effects on nutrient bioavailability, and antioxidant activity, as well as a brief description of the chemistry of polyphenols and their occurrence in plant foods.

Polyphenols: Chemistry, Dietary Sources, Metabolism, and Nutritional Significance

Antinutritional factors present in plant-derived alternate fish feed ingredients and their effects in fish

. A method for gravimetric determination of tannins based on binding with insoluble polyvinylpyrrolidone (PVP) is presented. The gravimetric method gives the absolute amount of tannins and avoids problems of standards associated with spectrophotometric methods. The method was applied to nine browse and tree leaves. The values obtained correlate significantly with tannins determined spectrophotometrically, protein precipitation capacities and protein precipitable phenotics. This method together with other tannin assays will be useful in nutritional studies. The present study also demonstrates the different behaviour of tannic acids from different commercial sources towards PVP suggesting the presence of different moieties in tannic acids from different commercial sources and even among batches from the same source thereby affecting the results obtained using the spectrophotometric methods. Use of well-defined tannic acid as a standard in spectrophotometric methods is suggested which will allow meaningful comparison of values obtained from different laboratories.

Gravimetric determination of tannins and their correlations with chemical and protein precipitation methods

Effects and fate of tannins in ruminant animals, adaptation to tannins, and strategies to overcome detrimental effects of feeding tannin-rich feeds

http://www.anuragaja.staff.ipb.ac.id/files/2012/10/Kumar_2010_FC_Phytate-human-rev.pdf

Dietary roles of phytate and phytase in human nutrition: A review

1. Chemical, Protein Precipitation and Bioassays for Tannins, Tannin Levels and Activity in Unconventional Feeds, and Efects and Fate of Tannins.- 2. Treatment of Plant Material, Extraction of Tannins, and an Overview of Tannin Assays Presented in the Manual.- 3. Measurement of Total Phenolics and Tannins Using Folin-Ciocalteu Method.- 4. Determination of Condensed Tannins (Proanthocyanidins).- 5. Gallotannin Determination by Rhodanine Assay.- 6. Gallotannin Determination Using HPLC.- 7. Determination of Hydrolysable Tannins (Gallotannins and Ellagitannins) after Reaction with Potassium Iodate.- 8. Determination of Protein-Precipitable Phenolics.- 9. Protein-Binding Capacity by Filter Paper Assay.- 10. Radial Diffusion Assay.- 11. Tannin Bioassay.- 12. Radiolabelled BSA Precipitation Method.- 13. Simplified Radiolabelled BSA Precipitation Method.- 14. Characterization of Phenolic Compounds by Thin Layer Chromatography (TLC).- 15. References.- 16. A Summary of Results from the First Phase of the Coordinated Research Project.- 17. List of Participants in the Co-Ordinated Research Project.

Quantification of Tannins in Tree and Shrub Foliage: A Laboratory Manual

Various tannin-complexing agents have been used to study the potential adverse effects of tannins on rumen metabolism. Using a method based on turbidity formation, the binding of various tannin-complexing agents (polyvinyl polypyrrolidone (PVPP), polyethylene glycol (PEG) of molecular weights 2000 to 35,000, and polyvinyl pyrrolidone (PVP) of molecular weight 10,000, 40,000 and 360,000) to tannins (tannic acid, purified tannins from quebracho (Aspidosperma quebracho) and leaves of trees and shrubs (Acioa barteri, Dichostachys cinerea, Guiera senegalensis, Piliostigma reticulatum)) was investigated at different pH values. The binding of all the tannins with PVPP was highest at pH 3-4 and lowest at pH 7. For all the pH range (3-7) studied, the binding of PEG was higher than that of PVP. For all the tannins except tannic acid, the binding to PVP was the same from pH 4.7 to 7. Similar results were observed for the PEG of molecular weight 6000 or higher for all the tannins except quebracho tannins for which the binding increased as the pH increased from 3 to 7. The binding with PEG 2000 decreased to a greater extent as the pH reached near neutral and for PEG 4000 this decrease was slightly lower. Addition of these tannin-complexing agents to the in vitro gas system resulted in higher gas production from tannin-rich feeds (increase varied from 0 to 135%). The PEG were the most effective followed by PVP and PVPP. The PEG 35,000 was least effective. The efficiency of other PEG was similar. The PEG 6000 was preferred to PEG 2000 or 4000 as its binding to tannins was higher at near neutral pH values. The gas production increased with an increase in the amount of PEG 6000 up to 0.6 g/40 ml rumen-fluid-containing medium containing 0.5 g tannin-rich feed, beyond which no increase was observed. The percentage increase in gas value at 24 h fermentation correlated significantly with tannin values, the highest correlation (r 0.95) being with protein precipitation capacity of tannins. The increase in gas production was associated with higher production of short-chain fatty acids with little change in their molar proportions, suggesting an increase in organic matter digestibility by inclusion of the PEG in tannin-rich feeds. However, apparent and true digestibilities were lower on addition of the PEG, due to the presence of PEG-tannin complexes in the residues. The use of this bioassay (percentage increase in gas production in the presence of PEG 6000) along with other tannin assays would provide a better insight into the nutritional significance of tannins.

/pdf/formation-of-complexes-between-polyvinyl-pyrrolidones-or-cwslmwkn8n.pdf

Formation of complexes between polyvinyl pyrrolidones or polyethylene glycols and tannins, and their implication in gas production and true digestibility in in vitro techniques

Harinder P. S. Makkar

Papers

Gravimetric determination of tannins and their correlations with chemical and protein precipitation methods

Effects and fate of tannins in ruminant animals, adaptation to tannins, and strategies to overcome detrimental effects of feeding tannin-rich feeds

Dietary roles of phytate and phytase in human nutrition: A review

Quantification of Tannins in Tree and Shrub Foliage: A Laboratory Manual

Formation of complexes between polyvinyl pyrrolidones or polyethylene glycols and tannins, and their implication in gas production and true digestibility in in vitro techniques