Phenols, inhibition

The most likely explanation for these results is that simple phenolics inhibit a very large array of enzymes in vitro. The most likely explanation for the CNS effects of Uncaria rynchophylla would be that indole alkaloids, such as dihydrocorynanteine or hirsutine (32), interact with the central neurotransmission and possibly the serotonin ergic system. 

Jo and others (2006) applied this assay to determine the antioxidant properties of methanolic extracts from Japanese apricot in chicken breast meat. Likewise, Pearson and others (1998) assessed two types of Japanese green tea from Japan and two of their active compounds, catechin and epicatechin, for their relative abilities to inhibit the oxidation of LDL. Also, Pearson and others (1999) assessed the ability of compounds in apple juices and extracts from fresh apple to protect LDL. Heinonen and others (1998b) observed that berry phenolics inhibited hexanal formation in oxidized human LDL. 

Aerobic The growth kinetics was described by an interacting, balanced and unstructured model characterized by phenol inhibition and oxygen limitation according to a double limiting kinetics [60, 62],... 

Equations (in the form T = A/B) for the Bounday Mechanisms of the Phenol-Inhibited Oxidation of RH [69]... 

Phenolic compounds naturally occurring in plants have induced many physiological responses that duplicate those reported for ozone and/or peroxyacetylnitrate (PAN). Chlorogenic acid is a competitive inhibitor of lAA-oxidase (35) and plant growth is adversely affected by increased concentrations of auxins (36). Concentrations of chlorogenic acid are increased in tobacco tissue exposed to ozone ( ) Phenols inhibit ATP synthesis (37), oxidative phosphorylation ( ) and SH enzyme activity (27) they increase respiration (38), reduce CO2 fixation (22), modify both membrane permeability (40) and oxidation rate of reduced NADH... 

Equation C (analogous to Equation A) can thus be derived for the theoretical rate of phenol-inhibited oxidation. 

If hydrogen abstraction from the zinc salt is fast enough to compete with that from the hydrocarbon substrate, then Scheme 2 amounts to a chain-transfer reaction similar to that illustrated in Reaction 9 for phenolic inhibition. Also, an alternative termination via the peroxyalkyl-ester radical (X) is conceivable since this radical might be expected to cyclize... 

FIGURE 14.2 Domains of realization of various mechanisms of phenol-inhibited hydrocarbon oxida-... 

In all cases, the authors propose technical solutions permitting one to reach non-negligible grafting rates knowing that the maj ority of natural starting compounds contain substances such as phenols inhibiting all polymerization of monomers when using conventional methods. So, ozonization... 

Phenol is redistilled under nitrogen, saturated with water or 10 mM Tris-HCl, 0.5 mM EDTA, pH 8.0, and stored frozen in small aliquots at -20°C. The addition of 0.1 % hydroxyquinoline to the phenol inhibits atmospheric oxidation. Also, the strong yellow colour helps in defining the interface between the phenol and aqueous layers after small-scale extractions. 

Inhibition of Chloride Passage Across Red Cell Membranes. Phenols inhibit the passage of chloride ion across the red cel 1 membrane. Motais et al. (15) examined this property for some of the same phenols (Table V) as those used for uncoupling studies by Stockdale Selwyn. A fair correlation can be obtained with log D and pKa (eq 19). Half of these phenols are not appreciably ionized under the experimental conditions. Since many nonacidic compounds are also active, we wondered if it really mattered for the unionized phenols whether the pKa was 9 or 10 or 11. Why not use Cp as a parameter which will parallel the pKa for ionized phenols, but will be zero for unionized phenols A superior treatment results when a Cp term is used, eq 20. Cp is the logarithm of the fraction of phenol unionized. The following interpretation is possible Cp is zero for unionized phenols... 

Furan is produced by the catalytic decarbonylation of 2-furaldehyde or by decarboxylation of 2-fiiroic acid with copper powder in quinoline. Furan is a colourless, water-insoluble liquid of pleasant odour, bp 32°C. Addition of hydroquinone or other phenols inhibits polymerization, which occurs slowly at room temperature. 

Phenols inhibit variations in potential. Antho-cyanins, in particular, consume oxygen rapidly, leading to a rapid drop in potential. Catechins and oligomeric procyanidins are more active than polymers. A wine with a high concentration of flavonols and not very highly condensed tannins consumes more oxygen than one that only contains condensed tannins. 

Many epidemiological studies have shown that green and black tea phenolics inhibit esophageal cancer. It is thought that tea can be beneficial in other ways as well. Studies are currently being conducted. 

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