Biotransformation, antioxidant activity

An interesting oxidative coupling mechanism has been proposed for the biotransformation of p-coumaric acid with peroxidase, leading to dimer and trimer structures with stronger antioxidant activities [38]. 

Biotransformation of (-)-nopol benzyl ether (455 ) was carried out at 30°C for 8-13 days at the concentration of 277 mg/200 mL medium by A. niger TBUYN-2, A. sojae IFO 4389, and A. usami IFO 4338. (-) Nopol benzyl ether (455 ) was biotransformed by A. TBUYN-2 to give 4-oxo-nopol-2, 4 -dihydroxy benzyl ether (456 ), and ( )-oxonopol (454 ). 7-Hydroxymethyl-l-/ -menthen-8-ol benzyl ether (457 ) was not formed at all (Figure 19.185). 4-Oxonopol-2, 4 -dihydroxybenzyl ether (456 ) shows strong antioxidative activity (IC50 30.23 pM). The antioxidative activity of 4-oxonopol 2, 4 dihydroxybenzyl ether (456 ) is the same as that of butyl hydroxyl anisole (BHA) (Noma and Asakawa, 2006b,c). 

Van DerMerwe J.D., Joubert E., Manley M., De Beer D., Malherbe C.J., Gelderblom W.C.A. In vitro hepatic biotransformation of aspalathin and nothofagin, dUiydrochalcones of rooibos (Aspalathus linearis), and assessment of metabolite antioxidant activity. Journal of Agricultural and food Chemistry, 58 2214-2220 (2010). 

L-Ascorbic acid serves as a reductant for several important enzymatic biotransformations. These characteristic biological activities result from its enediol structure, which confers a strong electron-donating ability. In addition, there is considerable evidence that biological antioxidants, including ascorbic acid, play an important role in the prevention of a large number of chronic diseases such as cancer, cerebral apoplexy, diabetes, myocardial damage, and AIDS.367,368... 

Little is known of the mechanisms by which environmental chemicals deplete retinoid stores. In many field studies there is evidence of increased activity of phase I and II biotransformation enzymes, and both are thought to directly metabolize retinoids. P450 enzymes also produce oxyradicals causing oxidative stress34,72,73, which may lead to retinoid use as antioxidants. There was evidence of oxidative stress and retinoid depletion in lake trout inhabiting an area contaminated with iron-ore mine tailings80, yet it is unlikely that this exposure would be associated with induction of phase I or II biotransformation enzymes. 

Raxofelast (IRFI 016 ( )-5-(acetyloxy)-2,3-dihydro-4,6,7-trimethyl-2-benzofiiranacetic acid) is a new hydrophilic vitamin E-hke antioxidant (Campo et al. 1997). Its activity depends on biotransformation to the deacetylated active metabolite IRFI 005, which has, therefore, been used in vitro in chemical, subcellular and cellular models. 

Feruloyl Esterases. Psychrophilic feruloyl esterases are employed in industry for biomass degradation, biotransformation, and isolation of ferulic acid derivatives useful as antioxidant, antimicrobial, and photoprotectant properties. For instance, one studied feruloyl esterase from the psychrophilic bacterium, P. haloplanktis TAG 125, is a family 1 carbohydrate esterase and displays significant activity toward pNP-acetate, a- and yS-naphthyl acetate, and 4-methylumbelliferyl p-trimethylammonio cinnamate chloride (a model substrate for determining ferulolyl esterase activity) (23). 

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