Stilbenes phenolics

Chlorophorin (= 2,4,3, 5 -Tetrahydroxy-4 -geranylstilbene) (stilbene, phenolic) Artocarpus incisus (Moraceae) [leaf] 5aR (37)... 

Extractives. Extractives are the extraneous plant components that can be dissolved away from the insoluble cell wall material. They include many different kinds of chemicals. The reactive functional groups encountered include acids, aldehydes, alcohols, stilbenes, phenols, quinones, and esters. 

SCHEME 16.6 The photochemistry stilbene phenols in lignin (Redrawn from Ruffin, B., and Castellan, A., Can J Chem 78, 73-83, 2000.)... 

Biological Effect Monoterpenes Diterpene Acids Stilbene Phenolics... 

These peroxides also form 1 1 adducts with styrene and form hydroben2oin diarenesulfonates with stilbenes. Di(ben2enesulfonyl) peroxide decomposes in water to phenol and sulfuric acid (33). 

The oxidation of 4-bromophenols to quinones can also be accompHshed using periodic acid (113). A detailed study of this reagent with stericaHy hindered phenols provided insight about the quinonoid product (114). The highest yield of 2,6-di-/-butyl-l,4-ben2oquinone [719-22-2] is for the case of R = OCH. The stilbene stmcture [2411-18-9] is obtained in highest yield for R = H. 

Photoaddhion of electron donor olefins such as vinyl ethers and stilbene to variously methyl and halogeno-substituted 1,4-benzoquinones resulted in the formation of dihydrobenzofurans via a dienone-phenol rearrangement of the primary product spirooxetanes <96H(43)619>. High-temperature water seems to be an alternative to use of acid catalysts or organic solvents by the cyclization of allyl phenyl ethers to dihydrobenzofurans <96JOC7355>. 

Food and plant phenolics are commonly detected using DAD detectors (Tan and others 2008). Photodiode array detection allows collection of the entire UV spectrum during the elution of a chromatographic peak, which makes it possible to identify a phenolic compound by its spectra. Simple phenols, phenolic acids, flavanones, benzophenones, isoflavones, and flavan-3-ols have maximum absorbance at 280 nm, hydroxycinnamic acids at 320 nm, flavonols, flavones, and dihydroflavonols at 365 nm, and anthocyanins at 520 nm (Ibern-G6mez and others 2002 Merken Hand Beecher 2000). Hydrolyzable tannins show a characteristic shoulder at 300 nm, suitable for identifying them (Arapitsas and others 2007). For stilbenes, maximum absorbance of trans-forms are at 306 nm and at 285 nm for cA-forms (Lamuela-Raventos and others 1995). 

Titanium ions can also he used as redox catalysts for the indirect cathodic reduction of nitro compounds (417). The electroreduction is carried out in an H20-H2S04/Ti(S04)2-(Pb/Cu) system at 45 80°C under 5 20Am . Nitrobenzene, dinitrobenzene, nitrotoluene, 2,4-dinitrotoluene, 2-nitro-m-xylene, nitro-phenol, 2,4-dinitrophenol, nitrophenetole, o-nitroanisole, 4-nitrochlorotoluene, ni-trobenzenesulfonic acid, and 4,4 -dinitro-stilbene-2,2 -disulfonic acid can all be reduced by this procedure to the corresponding amino compounds (418) in good yields (Scheme 146) [513-516]. Tin... 

Complex phenolics Coumarins, phenolic quinones, lignins, flavonoids, stilbenes, hydrolyzable tannins, condensed (or catechin) tannins, phenolic lipids... 

Cell walls in the necrotic tissue of these wounds were browned. Staining with diazotized Q-tolidine and toluidine blue confirmed the polypheno-lic nature of these brown depositions, which may have resulted from the polymerization of the stilbenes present in large quantities in spruce bark. Phenolic residues were deposited on the walls of certain cells internal to the necrotic tissues by 10 days after wounding. By 36 days these cells had become thick-walled. The precise nature of substances responsible for this thickening has not been determined, variable responses being obtained with histochemical tests for lignin (cf. Table I). Suberin was detectable in cells immediately underlying the thick walled cells, which corresponded to the... 

The technique of CPC was also employed as a key step in the purification of 26 phenolic compounds from the needles of Norway spruce (Picea abies, Pinaceae). An aqueous extract of needles (5.45 g) was separated with the solvent system CHCl3-Me0H-i-Pr0H-H20 (5 6 1 4), initially with the lower phase as mobile phase and then subsequently switching to the upper phase as mobile phase. Final purification of the constituent flavonol glycosides, stilbenes, and catechins was by gel filtration and semipreparative HPLC. °... 

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