Phenol solubilization

Substitution Reactions on Side Chains. Because the benzyl carbon is the most reactive site on the propanoid side chain, many substitution reactions occur at this position. Typically, substitution reactions occur by attack of a nucleophilic reagent on a benzyl carbon present in the form of a carbonium ion or a methine group in a quinonemethide stmeture. In a reversal of the ether cleavage reactions described, benzyl alcohols and ethers may be transformed to alkyl or aryl ethers by acid-catalyzed etherifications or transetherifications with alcohol or phenol. The conversion of a benzyl alcohol or ether to a sulfonic acid group is among the most important side chain modification reactions because it is essential to the solubilization of lignin in the sulfite pulping process (17). 

Lysol consists of a mixture of the three cresol isomers solubilized using a soap prepared from linseed oil and potassium hydroxide, to form a clear solution on dilution. Most vegetative pathogens, including mycobacteria, are killed in 15 minutes by 0.3—0.6% lysol. Lysol has a phenol coefficient of 2. Bacterial spores are very resistant. Lysol is also the name of a proprietary product, the formula of which has changed over the years other phenols have been substituted for the cresols. 

The phenols from the higher boiling point fractions have greater antimicrobial activity but must be formulated so as to overcome their poor solubility. A range of solubilized and emulsified phenolic disinfectants are available including the clear soluble fluids,... 

Clear soluble fluids. Cresol is a mixture of o-, m- and p-methyl phenol (Fig. 10.7A). Because of its poor solubility, it is solubilized with a soap prepared fiom linseed oil and potassium hydroxide. It forms a clear solution on dilution. This preparation, known as Lysol (Cresol and Soap Solution BP 1968) has been widely used as a general purpose disinfectant but has largely been superseded by less irritant phenolies. 

Figure 7 Mixld for iron (Fe) deficiency induced changes in root physiology and rhizo-sphere chemistry associated with Fc acquisition in strategy I plants. (Modified froin Ref. 1.) A. Stimulation of proton extru.sion by enhanced activity of the plasnialemma ATPase —> Felll solubilization in the rhizospherc. B. Enhanced exudation of reductanls and chela-tors (carhoxylates. phenolics) mediated by diffusion or anion channels Pe solubilization by Fein complexation and Felll reduction. C. Enhanced activity of plasma membrane (PM)-bound Felll reductase further stimulated by rhizosphere acidificalion (A). Reduction of FolII chelates, liberation of Fell. D. Uptake of Fell by a PM-bound Fell transporter.

Two hypotheses have been proposed to explain how phenolic acids directly increase membrane permeability. The first is that the compounds solubilize into cellular membranes, and thus cause a "loosening" of the membrane structure so that minerals can leak across the membrane (28-30, 42). Support for this hypothesis comes from the fact that the extent of inhibition of electrical potentials correlates with the log P (partition coefficient of a compound between octanol and water) for various benzoic and cinnamic acid derivatives (Figure 5). 

Polyphenol oxidase occurs within certain mammalian tissues as well as both lower (46,47) and higher (48-55) plants. In mammalian systems, the enzyme as tyrosinase (56) plays a significant role in melanin synthesis. The PPO complex of higher plants consists of a cresolase, a cate-cholase and a laccase. These copper metalloproteins catalyze the one and two electron oxidations of phenols to quinones at the expense of 02. Polyphenol oxidase also occurs in certain fungi where it is involved in the metabolism of certain tree-synthesized phenolic compounds that have been implicated in disease resistance, wound healing, and anti-nutrative modification of plant proteins to discourage herbivory (53,55). This protocol presents the Triton X-114-mediated solubilization of Vida faba chloroplast polyphenol oxidase as performed by Hutcheson and Buchanan (57). 

The versatility of permanganate as an oxidant has been greatly enhanced in the past decade by the observation that it can be solubilized in nonaqueous solvents with the aid of phase transfer agents (1). The literature contains descriptions for the use of this procedure for the oxidation of alkenes (2-13), alkynes (13-18), aldehydes (19), alcohols (20), phenols (21,22), ethers (23), sulfides (24,25), and amines (20,26). The dehydrogenation of triazolines has also been achieved by the use of permanganate and a phase transfer agent (27). ... 

Bacterial LPS used in this study were purchased from Sigma Chemical Co., St. Louis, MO., and were as follows Escherichia coli serotypes 0.26 B6 0127 B8 (prepared both by the phenolic and the TCA procedures) 0127 BB (by the butanol procedure) Serratia marcescens. and Shigella f1exneri. The LPS were solubilized in water and used as antigenic materials. 

Amines such as diethylamine, morpholine, pyridine, and /V, /V, /V, /V -tetramethylethylene-diamine are used to solubilize the metal salt and increase the pH of the reaction system so as to lower the oxidation potential of the phenol reactant. The polymerization does not proceed if one uses an amine that forms an insoluble metal complex. Some copper-amine catalysts are inactivated by hydrolysis via the water formed as a by-product of polymerization. The presence of a desiccant such as anhydrous magnesium sulfate or 4-A molecular sieve in the reaction mixture prevents this inactivation. Polymerization is terminated by sweeping the reaction system with nitrogen and the catalyst is inactivated and removed by using an aqueous chelating agent. 

At least three methods have been found to be applicable to the solubilization of chemically modified wood. The first experiment (4) (Direct method) employed severe dissolution conditions. For example, in 20-150 min at 200-250°C, wood samples esterified by a series of aliphatic acids could be dissolved in benzyl ether, styrene oxide, phenol, resorcinol, ben-zaldehyde, aqueous phenol solutions, etc. For carboxymethylated, ally-lated and hydroxyethylated woods, the conditions provided for dissolution in phenol, resorcinol or their aqueous solutions, formalin, etc., by standing or stirring at 170°C for 30 to 60 min (5). 

The bioavailability of silibinin from the extract is low and seems to depend on several factors such as (i) the content of accompanying substances with a solubilizing character such as other flavonoids, phenol derivatives, aminoacids, proteins, tocopherol, fat, cholesterol, and others found in the extract and (ii) the concentration of the extract itself (132,133). The systemic bioavailability can be enhanced by adding solubilizing substances to the extract (11,134). The bioavailability of silibinin can also be enhanced by the complexation with phosphatidylcholine or p-cyclodextrin, and possibly by the choice of the capsule material (135-137). The variations in content, dissolution, and (oral) bioavailability of silibinin between different commercially available silymarin products—despite the same declaration of content—are significant (138). 

Finally, several works have also implicated the nutrients P and Fe as possible inductors of changes in phenolic metabolism. However, studies of these relationships have been scarce. With regard to the former nutrient, P deficiency has been observed to raise the level of anthocyanins, but the reason for this rise remains unclear [4]. Meanwhile, low levels of Fe can increase the release of phenolic acids, presumably to help solubilize metals and thereby facilitate their uptake [135]. 

It is possible to oxidize alcohols in the presence of free phenols,217 although many times phenols are protected for solubilizing purposes. 

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