Plant polyphenols anthocyanins

Naturally occurring oxaarenes based on polycyclic pyrans encompass a plethora of structures including the plant polyphenols such as anthocyanins and a-tocopherol (vitamin E). Halogenated dibenzo-p-dioxins and dibenzofurans are formed both as by-products during the manufacture of chlorophenols, and from the incineration of organic matter in the presence of inorganic halides. 

Anthocyanidins from Ricciocarpos natans Proanthocyanidins from Stryphnodendron adstringens Proanthocyanidins from Cassipourea gummiflua Anthocyanins from plants Polyphenols from tea... 

Alai s rich blue-purple color advertises its high content of anthocyanins, a class of plant polyphenols under study as potential anti-disease agents. Five chemically different anthocyanins, particularly cyanidins, and at least a dozen other polyphenols have been isolated, including a high content of proanthocyanidins linked to possible anti-disease effects, such as in bacterial infections, onset of cancer, and inflammation. 

Polyphenoloxidase (PPO, EC 1.14.18.1) is one of the most studied oxidative enzymes because it is involved in the biosynthesis of melanins in animals and in the browning of plants. The enzyme seems to be almost universally distributed in animals, plants, fungi, and bacteria (Sanchez-Ferrer and others 1995) and catalyzes two different reactions in which molecular oxygen is involved the o-hydroxylation of monophenols to o-diphenols (monophenolase activity) and the subsequent oxidation of 0-diphenols to o-quinones (diphenolase activity). Several studies have reported that this enzyme is involved in the degradation of natural phenols with complex structures, such as anthocyanins in strawberries and flavanols present in tea leaves. Several polyphenols... 

Plants including fruits and vegetables are a vast reservoir of different phytochemicals. As stated previously, flavonoids are a diverse group of polyphenolic compounds, some of which are relatively stable, whereas others such as anthocyanins are labile under ambient conditions. Sample preparation is of paramount importance in studying flavonoids because a good method prevents compounds of interest from being degraded... 

Anthocyanins. Like the flavones. the anthocyanins are found throughout nature. This class uf polyphenolic compounds is responsible for the pink, red. violet, and blue colors found in plants. Like many other natural phenulic substances, anthocyanins occur in plants as glycosides the sugar-free anthocyanins are known as anihocyanidins. 

The Basic Protocol describes the reversed-phase HPLC analysis of polyphenolic compounds isolated into nonanthocyanin and anthocyanin fractions by solid-phase extraction. The Alternate Protocol describes the HPLC separation of acidic and neutral polyphenolic fractions. Fractionated samples are used because significant amounts of interfering compounds are extracted along with polyphenolics from plant materials. Solid-phase extraction with C18 Sep-Pak cartridges (vnitu.2) is used to selectively eliminate undesired components from crude extracts, and may minimize the effects of sample cleanup or preparation on the integrity of polyphenolics. The isolation and purification step using solid-phase extraction of polyphenolics will make possible the efficient analysis of individual polyphenolics by reversed-phase HPLC. 

This fractionation step may be optional. Some samples can be directly analyzed by HPLC after filtration (step 2) without solid-phase extraction. Anthocyanins that can be detected at 280 nm can interfere with the separation of some polyphenolics. If the analyst is interested in nonanthocyanin polyphenolics, and especially if plant materials containing high levels of anthocyanins are being analyzed, this fractionation technique should be utilized. 

Polyphenolic flavonoids compose the largest and the most studied group of plant phenolics. More than 4000 different flavonoids have been identified to date. Flavonoids are grouped into anthocyanins and anthoxantins. Anthocyanins are glycosides... 

The polyphenols are a series of phytochemicals synthesized by plants. They include the bioflavonoids anthocyanins, coumestanes, flavonoids, isoflavonoids, and stil-benes (Figure 4.1). Each bioflavanoid class is subdivided into other groups, e.g., flavones, flavans, flavanols, flavonols, and flavanones (Figure 4.2). Another class of polyphenol is the oligomeric polyphenols, such as the proanthocyanidins, found in the grape and various berries (black currant, blueberry, etc.). 

Although these same effects could be demonstrated with other polyphenol-enriched berries, the relatively higher concentrations of anthocyanins and proanthocyanidins in aronia simplify sourcing these polyphenols to one plant. 

Anthocyanins, flavanols and phenolic acids are the main polyphenols of grapes and grape-derived foods, responsible for their major organoleptic properties. Anthocyanins are directly involved in the color of most red fruits including grapes (7) while flavanols are thought to make an important contribution to the astringency and bitterness of plant derived foods (2,3). 

Some of these phenolic compounds are directly related to colours in plants, and in particular anthocyanidins ate natural pigments present as anthocyanins in plant tissues in glucoside forms with a C6-C3-C6 skeleton. Only a few phenolic compounds absorb tight in the visible range and anthocyanins are the only significant subgroup of polyphenols visible to the human eye (Brouillard et al. 

Plants - Lignin, tannins, and pigments, flavor components of spices (cinnamon oil, wintergreen oil, bitter almond, nutmeg, cayenne pepper, vanilla bean, clove, and ginger) are derived from coniferyl alcohol. Coniferyl alcohol, in turn, is derived from phenylalanine and tyrosine. Phenylalanine is also a precursor of plant pigments and related polyphenolic compounds called flavonoids. The biosynthetic scheme leads to a class of flavonoids called anthocyanins, which are common flower pigments.. An offshoot of this pathway leads to the synthesis of cocaine. 

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