Polyphenols occurrence

Jurd, L., Review of polyphenol condensation reactions and their possible occurrence in the aging of wines. Am. J. Enol. Vitic. 20, 197, 1969. 

Pietta, P., Minoggio, M., and Bramati, L., Plant polyphenols structure, occurrence and bioactivity, Studies in Natural Products Chemistry, 28 (Bioactive Natural Products (Part I)), Elsevier Science Publishers, Amsterdam, 257, 2003. 

The term, complex tannin, appears to be established as descriptor for the class of polyphenols in which a flavan-3-ol unit, representing a constituent unit of the condensed tannins (proanthocyanidins), is connected to a hydrolyzable (gallo-or ellagi-) tannin through a carbon-carbon linkage. Since the first demonstration of their natural occurrence, a considerable number of these unique secondary metabolites have been reported. " New additions (Table 11.17) to this series of compounds come exclusively from the groups of Nonaka and Nishioka, and Okuda and Yoshida in Japan. 

Solvent evaporation should be done under reduced pressures at low temperatures to minimize the degradation of extracted polyphenolics. Due to the likely occurrence of hydrolysis, isomerization, and polymerization at higher temperatures, temperatures for the evaporation process should be maintained at 40°C or below. 

Polyphenolic phytochemicals are ubiquitous in the plant kingdom. These important aromatic secondary metabolites of plants are consumed in significant amounts in daily life. Their occurrence among plant-based materials is frequently varied. They contribute to sensory qualities such as color, flavor, and taste of plant-based materials. The composition of polyphenolic phytochemicals is influenced by maturity, cultivar (Lee and Jaworski, 1987), cultural practices, geographic origin, climatic... 

Many excellent discussions of natural occurrence, structure, characterization, and analysis of phenolic compounds are available in the literature, and a series of books devoted to flavonoid chemistry has also been published. Detailed discussions on various chromatographic modes, including HPLC, GC, column chromatography (CC), capillary electrophoresis (CE), PC, and TLC, of simple phenolics and polyphenols are also presented in the recent book, Handbook of Food Analysis, volume 1, edited by Nollet (1). Due to their diversity and the chemical complexity of phenolic compounds, this chapter is limited to phenolic compounds that are considered to be important to foods and the food industry. 

Erickson M, Miksche GE (1974d) On the occurrence of lignin or polyphenols in some mosses and liverworts Phytochemistry 13 2295-2299... 

The conversion of animal hides into leather by treatment with water-soluble plant extractives has been practiced since antiquity. This process became known as tanning and obviously involved the reaction of a naturally occurring extractive, tannin, with the protein in the hide. We now know, of course, that tannins comprise a whole spectrum of chemical compounds, but generally they are polyphenolic and polymeric. Tannins have been isolated from a wide variety of raw materials, including insect galls, fruit skins, seed hulls, leaves, bark, and heartwood. Indeed, tannins are of nearly ubiquitous occurrence in higher orders... 

Grapes and berry fruits are rich sources of flavonoids and polyphenolics. Labor-intensive investigations over the years, initially from botanists and later from chemists and food scientists, provide a vast amount of knowledge about chemical structure, occurrence and stability of these compounds. As a consequence, food products, extracts, tinctures and dry powders are available with documented levels of flavonoids and other phenolics. 

Despite the current popularity of the polyphenol theory, a completely satisfactory scheme for the occurrence of humic and fulvic acids in diverse geologic environments has yet to be established. In practice, all pathways may be operative, but not to the same extent in all environments or in the same order of importance. A lignin pathway may-predominate in wet sediments, such as peats and swamps. The drastic conditions existing in soils under a harsh continental climate (e.g., some Mollisols) may favor humus synthesis by sugar-amine condensation. The disappearance of amino acids from buried sediments has been attributed to the formation of brown nitrogenous polyelectrolytes by reaction with reducing sugars (Stevenson, 1974). 

The oxidised polyphenols give the black colour, its aroma depends on the occurrence of a volatile oil and the tannins of a catechin type give the harsh taste. The caffeine content of a cup of tea is approximately 30—40 mg. 

In this chapter an attempt has been made to discuss the methods available for the isolation and analysis of higher plant cell walls. Because the structures and properties of the cell wall polymers from various tissue tyjDes show considerable differences, it is emphasized that, where possible, separation of the tissues in a plant organ prior to preparation of the cell walls is desirable. Attention is drawn to the problems associated with coprecipitation of intracellular compounds with cell wall polymers, particularly in view of the occurrence of small amounts of proteoglycan and proteoglycan-polyphenol complexes in the walls and the covalent attachment of phenolics and phenolic esters with some of the cell wall polymers of parenchymatous and suspension-cultured tissues. The preparation of gram quantities of relatively pure cell walls from starch- and protein-rich tissues is discussed at some length because of the importance of dietary fiber in human nutrition and an understanding of the composition, structure, and properties of dietary fiber would be hampered without such methods (Selvendran, 1984). 

About 80 lactones have been identified in tobacco smoke. These compounds, especially they-butyrolactones, andothers, have alkylating potential and some have been reported to be carcinogenic in laboratory animals [Lawley (6A12)]. [see also Appendix 2, pp. 387-394) in (1870)]. Quantitatively, about half the lactones in the smoke consist of y-butyrolactone [lARC (6A10)] (about 10 pg/cigarette) and its derivatives 5-valerolactone and some alkylated and unsaturated 5-valerolactones, as well as coumarin [see pp. 427-430 in Wynder and Hoffmann (4332)], 6-methylcoumarin, and 3,4-dihydrocoumarin have also been isolated [Schumacher et al. (3553)]. The occurrence of coumarin derivatives in smoke could be due to pyrolysis of polyphenols with a coumarin structure. .. or of plant extracts added to tobacco to enhance flavour [see pp. 427-430 in Wynder and Hoffmann (4332)]. Coumarin itself is carcinogenic to rats after oral administration [lARC (6A10)]. 

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