Veratryl alcohol oxidation products

These findings led to the proposition that the veratryl alcohol is degraded via the quinone intermediates (Figure 5) to CO2 through a series of transformations involving lignin peroxidase, perhydroxy radicals and the NADP-dependent aryl alcohol oxidoreductase. Veratraldehyde, the major product of lignin peroxidase catalyzed veratryl alcohol oxidation, is rapidly reduced back to veratryl alcohol it is the further metabolism of the side products of the oxidative process, viz. the quinones and lactones, that drives the overall transformation towards completion (34). 

In Figure 1 the isolated reaction products of the veratryl alcohol oxidation are depicted. 

D Annibale and his colleagues [99] performed experiments on VA oxidation using MnP from Lentinus edodes. They demonstrated two different types of reactions occurring in the presence and absence of GSH. When GSH was not included in the reaction mixture of MnP, Mn +, VA, H2O2 and chelator, aromatic ring cleavage, side chain oxidization and dimerization of VA were detected. (The main metabolite was y-muconolactone (58%), and three dimerization products were also observed [31] 2.3 and 1.8%, respectively). However, with the addition of GSH, veratraldehyde was the only metabolite formed. Veratryl alcohol oxidation was 32 and 14% in nonthiol and thiol mediated reactions, respectively. Under both conditions, oxidation depended strictly on the presence of both Mn + and H2O2. 

Another iron porphyrin complex with 5,10,15,20-tetrakis(2, 6 -dichloro-3 -sulfonatophenyl)porphyrin was applied in ionic liquids and oxidized veratryl alcohol (3,4-dimethoxybenzyl alcohol) with hydrogen peroxide in yields up to 83% to the aldehyde as the major product [145]. In addition, TEMPO was incorporated via... 

Activity Assays. The standard activity assay mixture of 3 ml contained about 0.1 U/ml lignin peroxidase, 0.4 mM veratryl alcohol (Fluka, purum >97%) and 0.1M sodium tartrate, pH 3.0. The reaction was started by adding 15 fil of 54 mM H2O2 to make a final concentration of 0.28 mM in the reaction. The production of veratraldehyde was followed by recording the change of absorbance for 12 seconds at 310 nm in a cuvette which was thermostated to 37°C. The reaction was started 24 seconds before the recording. One unit of lignin peroxidase is defined as the amount of enzyme required to oxidize one imol of veratryl alcohol to veratraldehyde in one minute. 

Metabolism of Monomeric Lignin Models. Leisola and coworkers (31,37) have reported on the products of the lignin peroxidase catalyzed oxidation of veratryl alcohol. Veratraldehyde was the major product (> 70% yield), together with a number of minor products, the quinones 13 and 14 and the ringopened lactones 16 and 17. In addition, Shimada et al. (38,39) showed that the 6-lactone 18 was also formed. Recently we obtained evidence that the ortho-quinone 15 and the 6-lactone 19 were also products of the lignin peroxidase catalyzed oxidation of veratryl alcohol (Schmidt ef al, Biochemistry, in press). Mechanisms for the formation of those compounds... 

I. 4-methoxyacetophenone (30 //moles) was added as an internal standard. The reaction was stopped after 2 hours by partitioning the mixture between methylene chloride and saturated sodium bicarbonate solution. The aqueous layer was twice extracted with methylene chloride and the extracts combined. The products were analyzed by GC after acetylation with excess 1 1 acetic anhydride/pyridine for 24 hours at room temperature. The oxidations of anisyl alcohol, in the presence of veratryl alcohol or 1,4-dimethoxybenzene, were performed as indicated in Table III and IV in 6 ml of phosphate buffer (pH 3.0). Other conditions were the same as for the oxidation of veratryl alcohol described above. TDCSPPFeCl remaining after the reaction was estimated from its Soret band absorption before and after the reaction. For the decolorization of Poly B-411 (IV) by TDCSPPFeCl and mCPBA, 25 //moles of mCPBA were added to 25 ml 0.05% Poly B-411 containing 0.01 //moles TDCSPPFeCl, 25 //moles of manganese sulfate and 1.5 mmoles of lactic acid buffered at pH 4.5. The decolorization of Poly B-411 was followed by the decrease in absorption at 596 nm. For the electrochemical decolorization of Poly B-411 in the presence of veratryl alcohol, a two-compartment cell was used. A glassy carbon plate was used as the anode, a platinum plate as the auxiliary electrode, and a silver wire as the reference electrode. The potential was controlled at 0.900 V. Poly B-411 (50 ml, 0.005%) in pH 3 buffer was added to the anode compartment and pH 3 buffer was added to the cathode compartment to the same level. The decolorization of Poly B-411 was followed by the change in absorbance at 596 nm and the simultaneous oxidation of veratryl alcohol was followed at 310 nm. The same electrochemical apparatus was used for the decolorization of Poly B-411 adsorbed onto filter paper. Tetrabutylammonium perchlorate (TBAP) was used as supporting electrolyte when methylene chloride was the solvent. 

Furthermore, oxidation of veratryl alcohol by sulfonated metalloporphyr-ins yields the same two major products observed when LiP is used [63a]. 

The electrical potential and/or current required for electroenzymatic treatment have been shown to be lower than those needed in electrochemical treatment, which are not economically viable for large-scale. Electroenzymatic oxidation by peroxidases was proposed for the oxidation of veratryl alcohol by LiP [40], Then, electroenzymatic reactors have been used for the treatment of petrochemical wastewater [91], dyes, and textile wastewater [90, 92, 118] and phenol streams [93] utilizing peroxidase immobilized onto inorganic porous Celite beads or directly onto the electrode. The integration of a second electrochemical reactor, which generated hypochlorite in the presence of sodium chloride, has been used for indirect oxidation of the reaction products of the electroenzymatic treatment [91]. 

Kervinen et al. (2005) investigated a homogeneous catalytic reaction, namely, the oxidation of veratryl alcohol to its aldehyde in the liquid phase. In this case, UV-vis spectroscopy, performed by immersing a fiber probe in the reacting medium, allowed detection of changes in the Co (salen) catalyst as well as monitoring of product formation. 

Meunier has developed model chemistry for peroxidases such as ligninase with KHSO5 as oxo-transfer oxidant and Fe or Mn-tetrasulfoporphyrin in aq. MeCN. These catalysts oxidize lignin models such as veratryl alcohol (3,4-methoxybenzyl alcohol) to give biologically relevant products such as quinones. 

An aryl-alcohol oxidase produced optimally under carbon limitation from Bjerkandera adusta oxidized a number of benzyl alcohols including 4-methoxybenzyl alcohol, 3,4-dimethoxybenzyl alcohol (veratryl alcohol), and 4-hydroxy-3-methoxybenzyl alcohol, with the production of H202 from 02 monosaccharides were not oxidized (Muheim et al. 1990). An aryl-alcohol oxidase from Pleurotus eryngii is a flavoprotein with range of substrates comparable to that from B. adusta (Guillen et al. 1992). 

Oxidation with ceric nitrate has been developed as a new degradative procedure in the study of bisbenzylisoquinoline alkaloids. This reagent splits lau-danosine to veratric aldehyde and the N-methyl-6,7-dimethoxy-3,4-dihy-droisoquinolinium ion, isolated as veratryl alcohol and N-methyl-3,4-dimethoxytetrahydroisoquinoline after reduction. In the same way, tetrandrine, hernandezine, and O-methylmicranthine have been degraded to the bis-tetra-hydroisoquinolines (48 R = H), (48 R = OMe), and (49), the second product in each case being the diphenyl ether (50). ... 

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