Polyphenols in plants

Methods used for the detection of PAs in cmde or partially purified extracts can also be adapted for post-column analysis after fractionation (see below). Direct quantitative analysis of PAs in crude grape phenolic extracts is often impossible due to the complex sample matrix. Thus, fractionation or purification is often necessary before analysis. The Folin-Ciocalteu and Pmssian Blue assays are widely used for the quantification of total polyphenols in plants [27,28]. These methods are not specific for PAs due to the reaction of other phenolic compounds with these reagents. 

In earlier times, thin-layer chromatography (TLC), polyamide chromatography, and paper electrophoresis were the major separation techniques for phenolics. Of these methods, TLC is still the workhorse of flavonoid analysis. It is used as a rapid, simple, and versatile method for following polyphenolics in plant extracts and in fractionation work. However, the majority of published work now refers to qualitative and quantitative applications of high-performance liquid chromatography (HPLC) for analysis. Llavonoids can be separated. 

Ellagitannins are among the most diverse and structurally complex class of polyphenolics in plants. They are important contributors to color, flavor and stability in fruits as well as oaked wine and distilled spirits. Recently, consumption of ellagitannins has also been linked to potential health benefits. The extraction, isolation, and identification... 

The presence of polyphenols in plant foods was largely influenced by genetic factors. 

The mechanism of green synthesis of gold and silver nanoparticles is due to the presence of polyphenol in plant extracts which is responsible for reduction of nanoparticles. The molecular mechanism which gives the antioxidant properties of gold and silver nanoparticles endorses reduction of Au ions to Au atoms and Ag ions to Ag atoms (Figure 6.8). This reduction takes place by abstraction of hydrogen because of the OH groups in the polyphenol... 

Watson RR (2014) Polyphenols in plants isolation, purification and extract preparation. Academic, London... 

Coulson CB, Davis RI, Lewis DA (1960) Polyphenols in plant, humus and soil. II. Reduction and transport by polyphenols of iron in model soil columns. J Soil Sci 11 ... 

Figure 1. Schematic outline of various products and associated enzymes from the shikimate and phenolic pathways in plants (and some microorganisms). Enzymes (1) 3-deoxy-2-oxo-D-arabino-heptulosate-7-phosphate synthase (2) 5-dehydroquinate synthase (3) shikimate dehydrogenase (4) shikimate kinase (5) 5-enol-pyruvylshikimate-3-phosphate synthase (6) chorismate synthase (7) chorismate mutase (8) prephenate dehydrogenase (9) tyrosine aminotransferase (10) prephenate dehydratase (11) phenylalanine aminotransferase (12) anthranilate synthase (13) tryptophan synthase (14) phenylalanine ammonia-lyase (15) tyrosine ammonia-lyase and (16) polyphenol oxidase. (From ACS Symposium Series No. 181, 1982) (62).

Duthie GG, Duthie SJ and Kyle JAM. 2000. Plant polyphenols in cancer and heart disease implications as nutritional antioxidants. Nutt Res Rev 13(1) 79-106. 

Lea AGH. 1992. Flavor, color and stability in fruit products the effect of polyphenols. In Hemingway RW and Leaks PE, editors. Plant Polyphenols. New York Plenum Press, pp. 827-847. 

In recent years, numerous papers have been published about one of the most important groups of phytochemicals, the polyphenols (Manach and others 2004). These compounds, which possess an array of healthy properties, but also some disadvantages that will be discussed in this chapter, are present in a variety of plants used in both human and animal diets. However, the structure of this type of compound means that they can be oxidized by several pro-oxidant agents. The objective of this chapter is to describe the main enzymatic agents responsible for the degradation of polyphenols. In order to understand the mechanisms of degradation that will be described in the following sections, a brief summary of the main properties of the polyphenols is required. 

Mayer AM. 2006. Polyphenol oxidases in plants and fungi going places A review. Phytochemistry 67 2318-2331. 

George S, Brat P, Alter P and Amiot MJ. 2005. Rapid determination of polyphenols and vitamin C in plant-derived products. J Agric Food Chem 53(5) 1370-1373. 

Boettcher AA, Targett NM (1993) Role of polyphenolic molecular-size in reduction of assimilation efficiency in Xiphister mucosus. Ecology 74 891-903 Bolwell GP, Butt VS, Davies DR, Zimmerlin A (1995) The origin of the oxidative burst in plants. Free Radical Res 23 517-532... 

Yates JL, Peckol P (1993) Effects of nutrient availability and herbivory on polyphenolics in the seaweed Fucus vesiculosus. Ecology 74 1757-1766 Zangerl AR, Bazzaz FA (1992) Theory and pattern in plant defense allocation. In Fritz RS, Simms EL (eds) Plant resistance to herbivores and pathogens. Chicago Press, Chicago, pp 363-391... 

Scalbert A (1992) Quantitative methods for the estimation of tannins in plant tissues. In Hemingway RW, Laks PE (eds) Plant polyphenols synthesis, properties, significance, vol 59. Plenum Press, New York, NY, pp 259-280... 

As its name suggests, supercritical fluid extraction (SEE) relies on the solubilizing properties of supercritical fluids. The lower viscosities and higher diffusion rates of supercritical fluids, when compared with those of liquids, make them ideal for the extraction of diffusion-controlled matrices, such as plant tissues. Advantages of the method are lower solvent consumption, controllable selectivity, and less thermal or chemical degradation than methods such as Soxhlet extraction. Numerous applications in the extraction of natural products have been reported, with supercritical carbon dioxide being the most widely used extraction solvent. However, to allow for the extraction of polar compounds such as flavonoids, polar solvents (like methanol) have to be added as modifiers. There is consequently a substantial reduction in selectivity. This explains why there are relatively few applications to polyphenols in the literature. Even with pressures of up to 689 bar and 20% modifier (usually methanol) in the extraction fluid, yields of polyphenolic compounds remain low, as shown for marigold Calendula officinalis, Asteraceae) and chamomile Matricaria recutita, Asteraceae). " ... 

Wolfender, J.-L. and Hostettmann, K., Liquid chromatographic-UV detection and liquid chromatographic-thermospray mass spectrometric analysis of Chironia (Gentianaceae) species. A rapid method for the screening of polyphenols in crude plant extracts, J. Chromatogr. A, 647, 191, 1993. 

Fulcrand, H. et al.. Electrospray contribution to structural analysis of condensed tannin oligomers and polymers. In Plant Polyphenols 2. Chemistry, Biology, Pharmacology, Ecology (eds G.G. Gross, R.W. Hemingway, T. Yoshida, and S.J. Branham), Kluwer Academic/Plenum Publisher, New York, 1999, p. 223. 

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