Phenols pyrogallol

Phytochemistry Underground parts of the plant contains tannins and phenols (pyrogallol and pyrocatechin). The aboveground parts contain flavone glycosides, saponins, alkaloids, and tannins (12-27.2 %). The whole plant is rich in tannins (Chumbalov et al. 1968 Chumbalov and Bikbulatova 1970 Plant Resources of the USSR 1988). 

Phthalic acid esters Plamitic, stearic, oleic acid Terephthalic acid Alkyl terephthalic acid esters 2,6-bis-( 1, l-methylethyl)-4-ethyl phenol Pyrogallol... 

Napthylamine Bordeaux, 4-hydroxyazobenzaie, pyrocatediol, 4-nitrophenole, ninhydrine, 2-naphtole, 1-naphtole, phenol, pyrogallol, hydroquinone. 

Phenols pyrogallol, protocatechuic acid, and p-trans-coumaric acid Triterpenes and lignans... 

Plicnoh.— If it is a free phenol, ether will extiact it from its ac ueous solution. If it is present in alkaline solution, the solution should first be saturated with cat bon dioxide. (n.B.—The alkaline solutions of catecliol, quinol and pyrogallol daiken rapidly m the air.) The following tests should then be applied. 

By boiling allyl bromide and pyrogallol dimethyl ether with acetone and potassium carbonate, he obtained a dimethoxyphenyl allyl ether, which was converted into dimethoxyallyl phenol by heating to 220°. On methylation this yields trimethoxyallyl benzene, identical with elemicin. 

Synthetic antioxidants are safer, cheaper and purer than natural antioxidants but, nevertheless, the majority of consumers still prefer natural antioxidants. This trend will surely persist in the near future. The mechanisms for the changes of synthetic antioxidants are well known, but the same cannot be stated in the case of natural phenolic antioxidants. They are usually pyrocatechol or pyrogallol derivatives, where the changes during oxidation could be different from those of synthetic antioxidants, which are mostly 1,4-substituted. 

Alkali-washed material, stabilised with 0.25% of pyrogallol, was distilled at 103°C/4 mbar until slight decomposition began. The heating mantle was then removed and the still-pot temperature had fallen below its maximum value of 135°C when the residue exploded violently [1], The presence of solid alkali [2] or 5% of phenolic inhibitor is recommended, together with low-temperature high-vacuum distillation, to avoid formation of acidic decomposition products, which catalyse rapid exothermic polymerisation. 

Two different approaches have been used to determine phenols without derivatization. In the first, the corresponding oxalate esters were synthesized in the traditional way (i.e., using oxalyl chloride and triethylamine) [111, 112]. Pen-tachlorophenol, 1-naphthol, bromofenoxim, bromoxynil, and /t-cyanophenol were treated this way, after which the POCL resulting from their reaction was measured in a static system. The second approach exploits the oxidation reaction between imidazole and hydroxyl compounds at an alkaline pH, where hydrogen peroxide is formed [113]. Polyphenols, e.g., pyrogallol, pyrocatechol, and dopa-... 

Finally gallein may be mentioned in it pyrogallol is the phenolic component. 

Wang et al. (62) reported the oxidative polymerization of a mixture of phenolic compounds in aqueous solution containing mont-morillonlte, illite, and kaolinite, each of which had been mixed with quartz in a 3 7 ratio, and by quartz alone. The mixture of phenolic compounds contained gallic acid, pyrogallol, protocatechuic acid, caffeic acid, orcinol, ferulic acid, p-coumaric acid, syringic acid, vanillic acid, and p-hydroxybenzoic acid. The oxidative... 

Phenols (p-cresol, guaiacol, pyrogallol, catechol) and aromatic amines (aniline, p-tolidine, o-phenyldiamine, o-dianisidine) are typical substrates for peroxidases [90 -109]. These compounds are oxidized by hydrogen peroxide or hydroperoxides under peroxidase catalysis to generate radicals, which after diffusion from the active center of the enzyme react with further aromatic substrates to form dimeric, oligomeric or polymeric products. 

The reaction mixture from acidified dihydroxyacetone also included a series of seven di- and tri-hydroxybenzenes (see Scheme 4), namely, 2,3-dihydroxytoluene (16), pyrocatechol (17), 3,4-dihydroxy toluene (19), 3,5-dimethyl-l,2-benzenediol (20), 1,2,3-trihydroxybenzene (pyrogallol) (21), 1,2,4-trihydroxy benzene (22), 3,4,5,6-tetrahydroxy-2-methy 1-acetophe-none, and 2,3-dihydroxy-5,6-dimethyl-p-benzoquinone. Many of these same phenolic compounds are present after hexoses are similarly treated... 

To elucidate some enzymatic characteristics of the isolated laccases I, II, and III, substrate specificities for several simple phenols, electrophoresis patterns, ultraviolet spectra, electron spin resonance spectra, copper content, and immunological similarities were investigated. Tyrosine, tannic acid, g c acid, hydroquinone, catechol, pyrogallol, p-cresol, homocatechol, a-naphthol, -naphthol, p-phenylenediamine, and p-benzoquinone as substrates. No differences in the specificities of these substrates was found. The UV spectra for the laccases under stucfy are shown in Figure 4. Laccase III displays three adsorption bands (280, 405, and 600nm), laccase II shows one band 280nm), and laccase I shows two bands (280 and 405 nm). These data appear to indicate differences in chemical structure. The results of the copper content analysis (10) and two-dimensional electrophoresis also indicate that these fractions are completely different proteins (10), Therefore, we may expect differences in substrate specificities between the three laccase fractions for more lignin-like substrates, yet no difference for some simple phenolic substrates. 

Phenolic acids and flavonoids can also act as chelating agents, complexing transition metals that are responsible of the initiation of peroxidative processes (Fenton and Haber-Weiss reactions). This property is much stronger in phenolics having a catechol, pyrogallol, or 3-hydroxy-4-carbonyl group [130]. 

Swain and Goldstein (6, 7) noted a rather large difference in the molar color yield from different phenols with the Folin-Denis reagent. They attributed this to differences in relative oxidation-reduction potentials of the different phenols, but under their conditions pyrogallol gave about half the color of catechol and more than resorcinol. However, they also reported that the molar absorptivity produced by a flavonoid was approximately equal to the sum of the values for the separate phenolic moieties which it contained. 

Table III. Molar Absorptivity in the Total Phenol Assay and Precipitability with Acidic Formaldehyde Pyrogallol Derivatives...

Phenols have definite protective action. Examples are P-hydroxybiphenyl, hydroquinine and pyrogallol, methylene di-b-napthol. 

Very simple sulfones have also been isolated from marine organisms. The isolation of sulfolane (290) from the sponge/tunicate composite Batzella spJLissoclinum sp. was the first report, either terrestrial or marine, of this compound as a natural product [213]. The pyrogallol Phenol B (291), obtained from the red alga Grateloupia filicina, was... 

The Reimer reaction is useless with compounds like phloroglueinol, pyrogallol, naphthols, poly-acid phenols of naphthalene, etc. 

Accordingly, where possible (for the p-hydroxybenzaldehydes), the aluminium chloride method (Reaction XXVIII.) should be used. The yields are better, the reactions go more smoothly, little resin being formed, while pyrogallols and naphthols, etc., also react. Unfortunately, though the non-formation of other than p-hydroxyaldehydes is often an advantage, it limits the scope of the reaction and necessitates the use of the Reimer method in many cases. It should be noted that the nitro-phenols do not condense with chloroform (B., 9, 423, 824 10, 1562 15, 2685). 

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