Plants polyphenols from

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

Polyphenolic secondary metabolites are a large and diverse group of chemical compounds which exist both in terrestrial and aquatic plants. Polyphenols from terrestrial plants are derived from gallic and ellagic acids, whereas the algal pol)q>henols are derived from polymerized... 

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. 

FIGURE 16.S Reactions catalyzed by the plant polyphenol oxidase, aureusidin synthase (AS), in the transformation of chalcones to aurones. (A) The biosynthesis of aureusidin from either tetra- or pentahydroxychalcone precursors through an ortho-diqmnone intermediate. (B) The aureusidin synthase-catalyzed formation of bracteatin from a pentahydroxychalcone precursor. 

Complex plant polyphenols readily and reversibly associate with proteins and they can precipitate them from dilute solution. This property is however a direct extrapolation of the characteristics of simple phenols themselves. The structural device represented by the plant polyphenols to a great extent obviates the need for a high molal concentration of phenol and it embodies the added feature that cross-linking between different molecular aggregates may be readily achieved. 

Polyphenolics constitute a wide range of chemical compounds composed of aromatic ring(s) with one or more hydroxyl substituents, including their functional derivatives. Methods for extraction and isolation of polyphenolics from plant material are described in this unit. Extraction and isolation are the first important steps for separation, characterization, and quantification of polyphenolics from plant material. Polyphenolics are often most soluble in organic solvents less polar than water. The solubility is dependent on the polar properties of the polyphenolics. The correct selection of the extracting solvent is not as simple as it may seem. Aqueous methanol is a popular choice of solvent (see Background Information). 

In this alternative procedure, absolute methanol rather than aqueous methanol is used to extract the polyphenolics from fresh plant material instead of freeze-dried samples. Raw plant material is washed, dried, and then immediately extracted. This protocol employs a blender to first macerate the plant material to increase the sample surface area for better contact of the solvent and the sample. 

The most common solvents used for the extraction of polyphenolics from plant material are methanol, ethanol, acetone, ethyl acetate, and their aqueous solvents. Aqueous methanol is a popular choice of solvent because it is efficient, has a high boiling point, and is eco-... 

Besides solid-phase extraction, column chromatography is also often used for cleanup and purification of polyphenolics from plant material. Ionic adsorbants (polyvinylpyrrolidone or PVP, polyamides, and Sephadex LH-20) and Amberlite XAD-2 resin have been used to isolate and purify polyphenolics from crude extracts. For the separation of polyphenolics from plant material, column chromatography using Sephadex LH-20, a gel-filtration matrix, is often used with various eluting solvents (Park and Lee, 1996). The most widely used solvents for column chromatography are aqueous methanol and aqueous ethanol. 

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. 

The chalcone synthase (CHS) (EC 2.3.1.74) superfamily of type III Polyketide synthases (PKSs) are pivotal enzymes in the biosynthesis of plant polyphenols. They are structurally and mechanistically different from the modular type I and the dissociated type II PKSs of bacterial origin the simple homodimer of 4CM-5 kDa proteins performs a complete series of decarboxylation, condensation, cyclization,... 

Plant extracts from which expressed proteins are separated are very different from animal biological liquids. Impurities include not only foreign proteins but also peculiar lipids and polysaccharides, depending on the plant organ. The presence of polyphenols must also be considered for separation by chromatography. One of questionable characteristics of antibodies expressed... 

Active medical research indicates that polyphenols from various plant foods hold the promise to favorably impact human health. For example, there is preliminary evidence that polyphenols act against these major threats ... 

The use of micronized/fine powder crospovidone as an active substance against diarrhoea depends on its ability to form complexes, as does the use of crospovidone ( PVPP ) in removing polyphenols from wine, beer and plant extracts. The... 

A major use of phenol is in phenol-formaldehyde adhesives for wood. Tannins are polyphenols from plants, as in bark,46 that may be able to replace phenol in such adhesives. A typical repeating unit is shown in (12.18). 

Free radicals are ubiquitous. They are found in living plants and for practical purposes are essential to all life. They also exist in plant material that is dried. These types of free radicals are called persistent free radicals and are normally associated with free radicals present in the structural biomass of the plant (polyphenols, carbohydrates, and lignin). The tobacco precursors of free radicals found in the particulate phase of cigarette mainstream smoke (MSS) are also long-lived, persistent free radicals but arise from the thermolysis of the tobacco biomass to form numerous types of phenolic and quinoidal free radicals [Wooten et al. (27A120)]. Short-lived free radicals are also present in the vapor phase... 

Bergenin, CmHwO, m. p. 238°, [ ]d —37.7° (ethanol), is a colorless, crystalline polyphenol which has been obtained from many plants, especially from Bergenia crassifoUa (syn. Saxifraga crassifolia)— from which it was first isolated. ... 

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