Odor precursors

Zeng, X.-N., Leyden, J. J., Brand, J. G., etal. (1992). An investigation of human apocrine gland secretion for axillary odor precursors. JournalofChemicalEcology 18,1039-1055. 

Latif A. and Salib A.G. (1975a) Odor and constitution of some natural products of roasted coffee beans. I. Chemical nature, functional groups and odor precursors. Alexandria J. Agric. Res. 23, 113-120. 

Akao, M., Shibuya, T., Shimada, S., Sakurai, H., and Kumagai, H. 2008. In vivo production of bioactive compounds from S-allyl-L-cysteine sulfoxide, garlic odor precursor, that inhibit platelet aggregation. J Clin Biochem Nutr Suppl 43 1-3. 

HLA Tarr. The MaiUard reaction in flesh foods. Food Technol 8 15-19, 1954. RL Macy, HD Naumann, ME Bailey. Water-soluble flavor and odor precursors of meat. I. Qualitative study of certain amino adds, carbohydrates, non-amino acid nitrogen compounds, and phosphoric acid esters of beef, pork, and lamb. J Food Sd 29 136-141, 1964. 

Environmental Aspects. Airborne particulate matter (187) and aerosol (188) samples from around the world have been found to contain a variety of organic monocarboxyhc and dicarboxyhc acids, including adipic acid. Traces of the acid found ia southern California air were related both to automobile exhaust emission (189) and, iadirecfly, to cyclohexene as a secondary aerosol precursor (via ozonolysis) (190). Dibasic acids (eg, succinic acid) have been found even ia such unlikely sources as the Murchison meteorite (191). PubHc health standards for adipic acid contamination of reservoir waters were evaluated with respect to toxicity, odor, taste, transparency, foam, and other criteria (192). BiodegradabiUty of adipic acid solutions was also evaluated with respect to BOD/theoretical oxygen demand ratio, rate, lag time, and other factors (193). 

Attempts have also been made to reduce the odor associated with the peracid in the home laundry. Use of a precursor that generates the peracid of a fatty acid can result in an objectionable odor in the wash bath (106). This odor is exacerbated by the higher piC of the peracid versus its parent acid resulting in a greater proportion of the peracid in the unionized and therefore less water-soluble form. To mitigate this circumstance, functionalization of the fatty tail typically alpha to the carbonyl has been utilized (112). The modifications include alpha-chloro and alpha-methoxy substituents on the parent acid portion of the precursor ester. 

Choline base [123-41 -17, [(CH2)3NCH2CH20H] 0H, triniethyl(2-hydroxyethyl)-ammonium hydroxide, derives its name from bile (Greek chole from which it was first obtained. This so-called free-ch oline is a colorless, hygroscopic Hquid with an odor of trimethyl amine. The quaternary ammonium compound (1) choline [62-49-7] or a precursor is needed in the diet as a constituent of certain phosphoHpids universally present in protoplasm. 

The earliest references to cinnamic acid, cinnamaldehyde, and cinnamyl alcohol are associated with thek isolation and identification as odor-producing constituents in a variety of botanical extracts. It is now generally accepted that the aromatic amino acid L-phenylalanine [63-91-2] a primary end product of the Shikimic Acid Pathway, is the precursor for the biosynthesis of these phenylpropanoids in higher plants (1,2). 

Preti G., Spielman A., Zeng X.-N. and Leyden J.J. (1995). The characteristic female axillary odors and their precursor proteins qualitative compraison to males. Chem... 

Spielman A., Sunavala G., Harmony J., Stuart W., et al. (1998). Identification and immunohistochemjcal localization of protein precursors to human axillary odors in apocrine glands and secretions. Arch Dermatol 134, 813-818. 

Spielman A., Zeng X., Leyden J. and Preti G. (1995). Proteinaceous precursors of human axillary odor — isolation of two novel odorant binding proteins. Experientia 51, 40-47. 

DF and its precursor, DC are organophosphonic acids. They will react with alcohols to form crude lethal nerve agents, such as crude GB. High overexposure may cause inhibition of cholinesterase activity. Although much less toxic than GB, DF and DC are toxic and corrosive materials. Because DF and DC are relatively volatile compounds, the primary route of exposure is expected to be the respiratory system. However, ingestion also results from inhalation exposures in animals and could occur in humans. DF and DC vapors have a pungent odor and may cause severe and painful irritation of the eyes, nose, throat, and lungs. Data provided is for DF only, DC has similar properties. 

Sulfur compounds such as furfuryl mercaptans have a rotten odor but in small amounts are coffee-like.15 Furfuryl mercaptan itself has an odor threshold of 0.005 ppb in water but at 10 ppb in water it imparts a distinctly stale odor.19 The particular precursors of furfuryl mercaptan seem to be the coffee cell wall material which contains both arabinogalactan as a pentose sugar source and protein such as glutathione.84 Other sulfur compounds such as kahweofuran and methyldithiofurans impart a meaty odor if their concentrations are high enough.19... 

Carotenoids are one of the most abundant groups of pigments found in nature. Every year more than 100 million tonnes of them are being synthesized in the biosphere. Nearly 600 molecular species of carotenoids are currently identified (Del Campo et al., 2007). As powerful antioxidants, vitamin precursors, natural colorants, and odorants they became a serious global market commodity accounting for almost 1 billion dollars of the yearly trade (BCC research, 2007). 

Lenthionine has the characteristic shiitake flavor. It is formed from the precursor, lentinic acid 14 by complex reactions involving a C-S lyase enzyme.30 Cyclic polysulfides occur in other Basidiomycete mushrooms (Genus Micromp-hale and Colly bid), in some red alga, and in seeds of Parkia speciosa. The latter contain lenthionine and 1,2,4-trithiolane (1,2,4-trithiacyclopentane) 17 as well as compounds with 4, 5, or 6 sulfur atoms.31 These seeds are valued in Indonesia for a unique, onion-like odor. Djenkolic acid and dichrostachinic acid S -[(2-carboxy-2-hydroxyethylsulfonyl)-methyl]cysteine are converted by a C-S lyase enzyme to cyclic polysulfides djenkolic acid yields 1,2,4-trithiolane and 1,2,4,6-tetrathiepane the latter is also formed from dichrostachinic acid.32... 

As you might guess from their names, these molecules have notably unpleasant odors. They were initially identified as degradation products of the action of bacteria on animal tissue. Cadaverine is also notably toxic. Putrescine is found in most cell types and is a precursor to spermidine. Note that both molecules have two amino groups. 

If you park at a trailer-type park with electric hook-ups and water you will most likely have neighbors. Do your work late at night so pungent or obvious odors (like ether) do not reach any outside noses. Try to work with precursors like isosafrole, which smells like black licorice, or some of the good smelling precursors. Good odors are not as suspicious as bad or strange odors. 

Besides steroids, axillary odor also contains normal, branched, unsaturated aliphatic acids with 6 to 11 carbon members. Most abundant is (E)-3-methyl-2-hexenoic acid. Both this compound and its (Z)-isomer are found in the aqueous phase hydrolysate and the aqueous phase incubated with bacteria. It is assumed that precursors are water soluble and converted to odoriferous compounds by the axillary flora (Zeng etal., 1992). 

CS076 Kobayashi, A., K. Kubota, Y. Joki, E. CS086 Wada and M. Wakabayashi. (Z)-3-hexenyl-beta-D-glucopyranoside in fresh tea leaves as a precursor of green odor. Biosci Biotech Biochem 1994 ... 

The concentrations of aldel des extracted in fraction FI at 207 bar/lS0°C were 3 to 8 times higher than those extracted at 345 bar/50°C The concentrations of 2,4-dienaIs which are responsible for the deep-fat fried odor of mai fiits and oils 14) were very high compared to similar compounds found in beef fat, and they were concentrated up to 34-fold in firaction FI compared to non-extracted control. 2,4-Decadienal (E,E) is an apparent precursor of 2-pentylpyridine, and it has also been found that the 2,4-dien contribute to fatty, oUy and tallowy odor of fats 36). 

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