Transformation of 3,5‐dimethoxy,4‐hydroxy cinnamic acid by polyphenol oxidase from the fungus Trametes versicolor: Product elucidation studies

Abstract

Sinapic acid (SA), 3,5-dimethoxy,4-hydroxy cinnamic acid, was incubated with a crude polyphenol oxidase from the fungus Trametes versicolor. Some products of this transformation were isolated and their structures identified using mass spectrometry, nuclear magnetic resonance and Fourier transform infrared spectroscopy, and X-ray crystallography. It was found that the enzymatic oxidation of SA includes two distinct phases. In the initial phase SA is enzymatically transformed to r-1H-2c,6c-bis-(4'-hydroxy-3', 5'-dimethoxyphenyl)-3,7-dioxabicyclo-[3,3,0]-octane-4,8-dione, dehydrodisinapic acid dilactone. The mechanism of this reaction may involve coupling of two phenoxy radicals by the beta-beta mode and subsequent intramolecular nucleophilic attack. In the second phase dehydrodisinapic acid dilactone is transformed by polyphenol oxidase into several intermediate products, including 4-(4-(3, 5-dimethoxy-4-oxo-2,5-cyclohexadienyliden)-1, 4-dihydroxy-(E)-2-butenylidene)-2,6-dimethoxy-2, 5-cyclohexadien-1-one. The final product of the overall transformation of SA is 2,6-dimethoxy-p-benzoquinone. The obtained results were used to propose a part of the transformation pathway for the enzymatic oxidation of SA by polyphenol oxidase.

Purification and characterization of a 32-kDa laccase-like stilbene oxidase produced by Botrytis cinerea Pers.:Fr.

“…The analysis method allowed 95% of resveratrol recovery (control) from the enzymatic mixture. Production of O-viniferin from the oxidation of resveratrol is in accordance with several authors [15,19], who described the oxidation to quinone of hydoxyphenols and the polymerization of these oxidation products.…”

Improving the functional expression of a Bacillus licheniformislaccase by random and site-directed mutagenesis

“…The main products of the laccases' reactions with sinapic acid, ferulic acid, and caffeic acid were dimers. The highest level of regioselectivity was obtained with sinapic acid, which was dimerized to dehydrodisinapic acid dilactone [ 36 ] (79%, m/z of 446) and two unknown products in a smaller quantity. Control reactions carried out in the absence of laccases did not lead to the oxidation of the compounds investigated.…”

Biotransformation of 3-hydroxydibenzo-a-pyrone into 3,8 dihydroxydibenzo-a-pyrone and aminoacyl conjugates by Aspergillus niger isolated from native shilajit

“…It was shown in earlier reports, that the enzymatic mechanisms involved in biotransformation by fungi include oxidation (Lacki and Duvnjak, 1998;Santos et al 2003), reduction or hydrolysis; formation of conjugates with products of intermediary metabolism such as acetic acid, cysteine, glucuronic acid, glycine and ornithine (Carey et al 2006). These mechanisms are two-phased, Phase I -metabolism (e.g.…”