Phenols accumulation

Effects of PEF on extracellular Tc and phenolics accumulation in suspension cultures of T. 

HowelF and Howell and Kremer found phenol accumulation assodated with the exposure of plants to ozone. Menser and Chaplin also reported an increase in the phenol content of tobacco leaves injured by ambient oxidants. Hoffman reported as much as an 80% increase in nicotine in leaves exposed to ozone at 0.24 ppm for 4 h. No increase was found after exposure to 0.06 or 0.12 ppm. Keen and Taylor found accumulation of several isoflavonoid compounds in soybean (Harosay 63) exposed to ozone. The presence of these compounds suggests a defense mechanism against ozone that is similar to that for disease resistance. 

Phenolic accumulation in B-deficient tissues can activate a group of enzymes that use these compounds as substrates. In B-deficient sunflower leaves, PPO activity progressively augments as symptoms characteristic of this deficiency appear. Plants with sensitivity to B deficiency differ in PPO activity. The accumulation of phenolics and PPO activity are reportedly greater in more sensitive plants, such as sunflower, than in less deficiency-sensitive plants, such as com (Zea mays) [125]. 

Phenolic compounds in plants play a role in disease resistance (Morandi, 1996). Mycorrhizal plants of maize accumulated more phenolic compounds p-hydrocinnamic acid and ferulic acid in roots than non-mycorrhizal plants (Huang, 2003). Mycorrhizal Ri T-DNA transformed carrot roots accumulated more phenolic compounds when challenged by Fusarium oxysporum (Benhamou et al., 1994). All cultivars of pea colonized with G. mosseae accumulated more phenolic acids, and total phenolic accumulation were closely correlated to disease intensity (Singh et al., 2004). 

With the establishment of the primary phototriplet reduction mechanism we now turn to the explanation for the effect of flow rates and the formation of polarized phenoxy radicals. Since reaction [2] is a relatively fast secondary process it is readily understood that the observation of the primary ketyl radicals will be dependent upon flow rate. The triplet polarization (E) of the secondary phenacyl radical should not have been affected but the increased contribution of the E/A Radical-Pair polarization altered the overall appearance of the polarization pattern. The diffusion model of the Radical-Pair theory relates the E/A polarization magnitude to the radical concentration within the reaction zone. Since the phenacyl radical is considered to be very chemically reactive, and the product phenol "accumulated" within the reaction zone is also a much better hydrogen donor, the following reactions will proceed within the reaction zone ... 

In the structure CS2 (Figure 5.24) the phenol fresh feed is raised to 165 kmol/h, while the hydrogen flow to reactor is kept constant at the value from the nominal steady state at 388kmol/h. This control structure does not work. Phenol accumulates in recycle because the hydrogen is insufficient for reaction, leading to plant upset. 

Aliette (aluminum tris-0 ethylphosphonate) has been reported to enhance defense reactions and phytoalexin accumulation in grapes and tomatoes in response to infection by Plasmopara viticola and Phytophthora spp., respectively, and to trigger phenolic accumulation and hypersensitive cell death in tomatoes, peppers, and beans in response to infection while possessing little direct fungitoxicity (116,117). However, recent data cast doubt on the earlier reports of the low activity of Aliette as an inhibitor of Phytophthora sporulation mi vitro (118), and have attributed the protective properties of the compound to phosphorous acid which is formed in plant tissues or in certain buffer solutions of Aliette (119,120). Toxicity of phosphorous acid to Oomycetes is reversible by phosphate ion, and this may explain Aliette s lack of fungitoxicity in certain growth media. 

When 2-propanol is oxidized in the presence of benzene, the latter is hydroxylated to form phenol [116]. Phenol is oxidized in the course of the reaction giving a resin displaying a strong inhibiting action. Hydroxyla-tion of benzene is observed in 2-propanol oxidation at temperatures of 150—200°C. Phenol accumulates in concentrations up to 0.2 mole l-1. The ratio of rate coefficients is... 

Minimal processing of carrots induces phenylalanine ammonia lyase (PAL) activity and phenolics accumulation. In shredded carrots, chlorogenic acid, which is rapidly accumulated, represents 60% of the total phenolics. In addition traces of 3 -caffeoylquinic and 4 -caffeoylquinic acids are biosynthesised, and 3, 4 -dicaffeoylquinic and 3, 5 -dicaffeoyl quinic acids also accumulate [44]. p-Hydroxybenzoic acid derivatives are also biosynthesised but more slowly, and are related to defence against microbial attack (phytoalexin response), the degree and speed of which depends on the cultivar [45],... 

The distribution of the phenols into sediment and a polyethylene liner sample is given in Figure 10.7. So little compound was associated with the liner that it was not considered a significant factor in accounting for their overall fate. Pentachloro-phenol accumulated in sediments to a greater extent than the tetrachlorophenol. This tendency is illustrated by the fact that at 15 days the concentration of the former in the wet sediment was 8.8 pg kg with a water column concentration of 1.8pg L while the corresponding values for the tetra phenol were 2.0 pg kg and 28.6 pg The sediments contained >90% water and the amount of tetrachlorophenol in sediment can be accounted for by what is dissolved... 

This points to a regulatory function of PAL in the flow of carbon from phenylalanine to phenolics derived from cinnamic acid. However, in a recent review article Margna (2) has advanced arguments that phenol accumulation in plant cells is controlled at the level of substrate (phenylalanine) supply. 

His arguments were (a) the lack of a correlation between changes in PAL level and in the rate of phenol accumulation as observed in a niiraber of cases,(fc) the large surplus of PAL one finds in many plants - often the lowest level of PAL activity was more than sufficient for the maximum rate of phenol synthesis under optimum conditions -and (o) the fact that feeding of phenylalanine to plant tissues generally led to increased accumulation of phenolics but to lower PAL levels. In this paper arguments... 

Palacio L, Cantero JJ, Cusido R, Goleniowski ME (2010) Effect of inoculum age on kinetic of biomass formation and phenolic accumulations in Larrea divaricata Cav. cell suspension culture. Mol Med Chem 21 64... 

Cle C, Hill LM, Niggeweg R, Martin CR, Guisez Y, Prinsen E, Jansen MAK (2008) Modulation of chlorogenic acid biosynthesis in Solarium lycopersicum-, consequences for phenolic accumulation and UV-tolerance. Phytochemistry 69 2149-2156... 

Yamaguchi T, Fukuzumi T, Yoshi T 1986 Effects of phytohormones on phenolic accumulations in callus of Eucalyptus robusta. Mokuzai Gakkaishi 32 209-212... 

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