Phytochemicals fermentation

Levene and Walti also reduced phytochemically l-hydroxy-3-buta-none to the levorotatory 1,3-butanediol and l-hydroxy-2-heptanone to the dextrorotatory 1,2-heptanediol. It seems that the optically active glycols that are obtained by bioreduction of hydroxy ketones with fermenting yeast are configurationally related. But the 1,3-butanediol that is obtained by the reduction of the l-hydroxy-3-butanone has the opposite configuration from the product of bioreduction of the isomeric d,Z-acetaldol (see p. 81). 

After phytochemical reduction was noted in the case of aldehydes and ketones, interest arose in the behavior of fermenting cells toward compounds containing several carbonyl groups per molecule, such as diketones and quinones. This class deserves special consideration because the simplest representative, diacetyl, as well as its products of reduction, acetylmethylcarbinol (3-hydroxybutanone) and 2,3-butylene glycol, are connected with the metabolism of numerous cells quinones also are biologically important. 

The first experiments made by Neuberg and Nord with the simplest diketone, diacetyl, showed at once that this substance can be hydrogenated phytochemically with comparitive ease. Acetylmethylcarbinol appears as an intermediate (see below), and the end product of reduction is asymmetric and levorotatory. Reduction was effected by the action of fermenting yeast on diacetyl. The 2,3-butanediol that is formed can be isolated by alcohol-ether extraction of the fermentation mixture after concentration in the Faust-Heim apparatus or by steam distillation in an atmosphere of carbon dioxide under ordinary pressure it is then carefully concentrated with the birectifier and obtained in the pure state by final fractionation. 

The phytochemical reducibility of quinones was first demonstrated in the case of p-xyloquinone. This compound is worthy of interest since it is very easily formed from diacetyl by purely chemical means through a type of aldol condensation followed by ring closure. It is reduced to p-xylohydroquinone by fermenting yeast. Benzoquinone, thymoquinone and a-naphthoquinone similarly yield the corresponding hydroquinones. Tetrabromo-o-quinone and anthraquinone proved resistant to attack, while phenanthraquinone could be reduced phyto-chemically to phenanthrahydroquinone in poor yield (9%). Phytochemical reduction can also be accomplished in the dicyclic terpene series. According to unpublished experiments by Neuberg and Peiser, 2,3-dihy-... 

Ideas regarding the mechanism of phytochemical reduction of olefins have been advanced by Fischer and Eysenbach. They also point out that just as in the case of the simple disproportionations in the course of sugar degradation (for example, the second and third forms of fermentation), saturation of the olefinic linkage is at an optimum in the weakly alkaline range, at about pH 8.5. 

The hydrolytic reaction would not have been of interest, while the reductive formation would bring the process in line with other analogous phytochemical reductions. The fact that the presence of sodium sulfite in the fermentation mixture has been established, while sulfate is absent, proves that a true hydrogenation does take place. Previously, it was not considered that two possibilities exist for this reaction. It has been ascertained analytically that the precipitate produced by the fermenta-... 

Fermenting yeast is able to reduce added nitrobenzene to the corresponding amine, aniline, to quite a considerable extent. Part of the added nitrobenzene remains unattacked, but 70% of it could be converted to aniline. Since a direct reduction of the nitro group to the amino group is improbable, Neuberg and Welde tried phytochemical treatment of the possible intermediaries, namely, nitrosobenzene and phenylhydroxylamine on the one hand and azoxybenzene and azobenzene on the other hand. 

The connection of the aromatic mono-, di- and tri-nitro compounds with phytochemical reduction follows from their activating action in alcoholic fermentation, known for a quarter century.The same applies equally to the excellent activating effect of cinnamic aldehyde its behavior during phytochemical eduction is described on pages 79 and 105. 

Phytochemical reduction of tetrazolium salts has been observed by Kuhn and Jerschel. If 2,3,5-triphenyl tetrazolium chloride is added to fermenting yeast the corresponding formazan is formed. Like most formazyl compounds it has a red color. 

The long-known stimulating effect of mono- and polynitro com-pounds on the onset of fermentation in yeast maceration juice has been reinvestigated by Vandendriessche. The induction time is shortened significantly by 2,4- or 2,5-dinitrophenol, while 2,6-dinitro-phenol did not show such an effect. The influence is evident when using as substrates the fermentable hexoses and D-fructose-6-phosphate, but not hexose diphosphate. According to MarkoviCev a stimulation of the oxidation processes can be proved thereby. It is probable that these effects are related to the known phytochemical reduction of nitro compounds (see pp. 98 and 99). 

Effect of fermentation on the phytochemical contents and antioxidant properties of plant foods... 

Effect of fermentation on phytochemical profiles of plant foods and the bioavailability of nutrients... 

The phytochemicals that exist naturally in plant foods are mostly in bound form and less bioavailable than the free form. Bio-processing methods such as fermentation have long been adapted to improve the nutritive value of plant foods. With the aid of microorganisms capable of modifying plant constituents, such as releasing the chemically bound compound during fermentation, the fermented plant foods thereby are enriched with phytochemical contents with improved bioavailability and bioactivity, in addition to the altered ratio of nutritive and anti-nutritive components of plants, as well as improved texture and organoleptic characteristics. 

Fermentation often increases the bioavailability of phytochemicals by releasing the esterifled compounds to free form. Only the free and conjugated phenolic acid forms were found to be bio-accessible (Patel, 2012). Oboh, Ademiluyi, and Akindahunsi... 

Health-promoting effects of fermented plant foods a case of phytochemical and antioxidant property changes... 

The levels and bioavailability of phytochemicals in plant foods such as legumes, cereals, vegetables, herbs and fraits can be greatly affected by processing such as fermentation. This subsequently leads to increased antioxidant properties, which may be benehcial for treatment and/or prevention of diseases such as atherosclerosis and cancer. Thus fermentation, especially with probiotics (functional microbes), can serve as an important process not only for preservation but also for production of functional foods with enhanced bioactive and antioxidant properties. 

Hubert, J., Monique, B., Frangoise, N., Frau9oise, R, Jean, D. (2008). Effects of fermentation on the phytochemical and antioxidant properties of soy germ. Food Chemistry, 109, 709-721. 

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