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D- and L-lactaldehyde are also good substrates for aldose reductase. The aldose reductase-catalyzed reduction of methylglyoxal produces 95% acetol, 5% D-lactaldehyde. (PMID: 1537826). D-lactaldehyde is an intermediate in the pyruvate metabolic pathway. Pyruvaldehyde is irreversibly produced from D-lactaldehyde via the enzyme glyoxylate reductase (NADP+, Swiss-Prot: Q5T945).

L-lactaldehyde is an intermediate metabolite in the pyruvate metabolism pathway. L-lactaldehyde is irreversibly produced from pyruvaldehyde via the enzyme aldehyde reductase (EC:1.1.1.21) which is then irreversibly converted to propylene glycol via aldehyde reductase (EC:1.1.1.21).

3-Hydroxypropanal is a broad-spectrum antimicrobial substance termed reuterin produced by Lactobacillus reuteri. L. reuteri resides in the gastrointestinal tract of healthy humans and animals, and is believed to. function as a symbiont in the enteric ecosystem. Synthesis of such an antimicrobial substance by an enteric resident raises a number of interesting questions and possibilities as to the role these residents may play in the health of the host. (PMID 3245697). In vivo, glycerol is converted in one enzymatic step into 3-Hydroxypropanal. The 3-Hydroxypropanal -producing Lactobacillus reuteri is used as a probiotic in the health care of humans and animals. 3-Hydroxypropanal forms, together with Hydroxypropanal-hydrate and Hydroxypropanal-dimer, a dynamic, multi-component system (Hydroxypropanal system) used in food preservation, as a precursor for many modern chemicals such as acrolein, acrylic acid, and 1,3-propanediol (1,3-PDO), and for polymer production. 3-Hydroxypropanal can be obtained both through traditional chemistry and bacterial fermentation. To date, 3-HPA has been produced from petrochemical resources as an intermediate in 1,3-PDO production. The biotechnological production of 3-Hydroxypropanal from renewable resources is desirable both for use of 3-Hydroxypropanal in foods and for the production of bulk chemicals. The main challenge will be the efficient production and recovery of pure 3-Hydroxypropanal. (PMID 14669058).

Glycidol is an odorless clear colorless liquid. (NTP, 1992) Glycidol is an epoxide and a primary alcohol. It is functionally related to a 1,2-epoxypropane. Glycidol is slightly viscous, colorless and odorless liquid cyclic ether. Glycidol is used as a stabilizer for natural oils and vinyl polymers, as an alkylating agent, a sterilant, a demulsifier, a dye-leveling agent and it is also used as an intermediate in the synthesis of glycerol, glycidyl ethers and amines. Exposure to Glycidol irritates the skin, eyes, and mucous membranes and depresses the central nervous system in humans. Glycidol induces mutations in human lymphocytes and is reasonably anticipated to be a human carcinogen. (NCI05) Glycidol can cause cancer according to The National Toxicology Program. Glycidol is an organic compound that contains both epoxide and alcohol functional groups. Being bifunctional, it has a variety of industrial uses. The compound is a slightly viscous liquid that is slightly unstable and is not often encountered in pure form. Glycidol is an irritant of the skin, eyes, mucous membranes, and upper respiratory tract. Exposure to glycidol may also cause central nervous system depression, followed by central nervous system stimulation.

Hydroxyacetone, also known as acetol or acetone alcohol, belongs to the class of organic compounds known as alpha-hydroxy ketones. These are organic compounds containing a carboxylic acid, and an amine group attached to the alpha carbon atom, relative to the C=O group. Hydroxyacetone exists in all living organisms, ranging from bacteria to humans. Hydroxyacetone is a sweet, caramel, and ethereal tasting compound. hydroxyacetone has been detected, but not quantified in several different foods, such as bog bilberries, cardoons, amaranths, black salsifies, and komatsuna. This could make hydroxyacetone a potential biomarker for the consumption of these foods. Hydroxyacetone is an intermediate in glycine, serine, and threonine metabolism.

A member of the class of propanals obtained by the reduction of the carboxylic group of lactic acid (2-hydroxypropanoic acid)." []

Methyl acetate belongs to the class of organic compounds known as carboxylic acid esters. These are carboxylic acid derivatives in which the carbon atom from the carbonyl group is attached to an alkyl or an aryl moiety through an oxygen atom (forming an ester group). Methyl acetate is present in apple, grape, banana and other fruits. Methyl acetate is a flavouring ingredient and it is an ester that, in the laboratory, is synthesized from acetic acid and methanol in the presence of strong acids such as sulfuric acid in an esterification reaction. In the presence of strong bases such as sodium hydroxide or strong acids such as hydrochloric acid or sulfuric acid it is hydrolyzed back into methanol and acetic acid, especially at elevated temperature. Methyl acetate, also known as acetic acid methyl ester or methyl ethanoate, is a clear, flammable liquid with a characteristic, not unpleasant smell like certain glues or nail polish removers. Methyl acetate has characteristics very similar to its analog ethyl acetate. Methyl acetate is used as a solvent in glues, paints, and nail polish removers, in chemical reactions, and for extractions. Methyl acetate is a non-polar (lipophilic) to weakly polar (hydrophilic) aprotic solvent. Methyl acetate has a solubility of 25% in water at room temperature. At elevated temperature its solubility in water is much higher. Methyl acetate is not stable in the presence of strong aqueous bases or acids. The conversion of methyl acetate back into its components, by an acid, is a first-order reaction with respect to the ester. The reaction of methyl acetate and a base, for example sodium hydroxide, is a second-order reaction with respect to both reactants

Propionic acid (PA) is an organic acid. It exists a clear liquid with a pungent and unpleasant smell somewhat resembling body odor. Propionic acid (PA) is widely used as an antifungal agent in food. It is present naturally at low levels in dairy products and occurs ubiquitously, together with other short-chain fatty acids (SCFA), in the gastro-intestinal tract of humans and other mammals as an end-product of the microbial digestion of carbohydrates. The metabolism of propionic acid begins with its conversion to propionyl coenzyme A, the usual first step in the metabolism of carboxylic acids. Since propionic acid has three carbons, propionyl-CoA cannot directly enter either beta oxidation or the citric acid cycles. In most vertebrates, propionyl-CoA is carboxylated to D-methylmalonyl-CoA, which is isomerised to L-methylmalonyl-CoA. Propionic acid has significant physiological activity in animals. Propionic acid is irritant but produces no acute systemic effects and has no demonstrable genotoxic potential (PMID 1628870). The human skin is host of several species of bacteria known as Propionibacteria, which are named after their ability to produce propionic acid. The most notable one is the Cutibacterium acnes (formerly known as Propionibacterium acnes), which lives mainly in the sebaceous glands of the skin and is one of the principal causes of acne. Propionic aciduria is one of the most frequent organic acidurias, a disease that comprise many various disorders. The outcome of patients born with Propionic aciduria is poor intellectual development patterns, with 60% having an IQ less than 75 and requiring special education. Successful liver and/or renal transplantations, in a few patients, have resulted in better quality of life but have not necessarily prevented neurological and various visceral complications. These results emphasize the need for permanent metabolic follow-up whatever the therapeutic strategy (PMID 15868474). Decreased early mortality, less severe symptoms at diagnosis, and more favorable short-term neurodevelopmental outcome were recorded in patients identified through expanded newborn screening. (PMID 16763906)↵ When propionic acid is infused directly into rodents' brains, it produces hyperactivity, dystonia, social impairment, perseveration and brain changes (e.g., innate neuroinflammation, glutathione depletion) that may be used as a means to model autism in rats. Propionic acid is a metabolite of Bacteroides, Clostridium, Dialister, Megasphaera, Phascolarctobacterium, Propionibacterium, Propionigenum, Salmonella, Selenomonas and Veillonella (https://www.mdpi.com/2311-5637/3/2/21).

Ethyl formate, also known as areginal or ethyl methanoate, belongs to the class of organic compounds known as carboxylic acid esters. These are carboxylic acid derivatives in which the carbon atom from the carbonyl group is attached to an alkyl or an aryl moiety through an oxygen atom (forming an ester group). Ethyl formate is an alcohol, bitter, and cognac tasting compound. Ethyl formate has been detected, but not quantified, in several different foods, such as citrus, pineapples, apples, fruits, and pomes. This could make ethyl formate a potential biomarker for the consumption of these foods. It occurs naturally in the body of ants and in the stingers of bees. Ethyl formate has the characteristic smell of rum and is also partially responsible for the flavor of raspberries. The U.S. National Institute for Occupational Safety and Health (NIOSH) also considers a time-weighted average of 100 ppm over an eight-hour period as the recommended exposure limit. Ethyl formate is an ester formed when ethanol (an alcohol) reacts with formic acid (a carboxylic acid). According to the U.S Occupational Safety and Health Administration (OSHA), ethyl formate can irritate eyes, skin, mucous membranes, and the respiratory system of humans and other animals; it is also a central nervous system depressant. Ethyl formate has been identified in dust clouds in an area of the Milky Way galaxy called Sagittarius B2 and it is among 50 molecular species identified using the 30 metre IRAM radiotelescope. In industry, it is used as a solvent for cellulose nitrate, cellulose acetate, oils, and greases.

Dioxolane appears as a clear colorless liquid. Slightly denser than water. Vapors heavier than air. 1,3-dioxolane is a cyclic acetal that is pentane in which the carbon atoms at positions 1 and 3 are replaced by oxygen atoms respectively. It is a dioxolane and a cyclic acetal.

A cyclic acetal that is pentane in which the carbon atoms at positions 1 and 3 are replaced by oxygen atoms respectively." []