2-Nonenal
Encyclopedia
2-Nonenal is an unsaturated
Saturation (chemistry)
In chemistry, saturation has six different meanings, all based on reaching a maximum capacity...

 aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....

 which some research has associated with human body odor
Body odor
Body odor or body odour, sometimes colloquially abbreviated as B.O., is the smell of bacteria growing on the body. The bacteria multiply rapidly in the presence of sweat, but sweat itself is almost completely odorless to humans....

 alterations during aging. The substance is also an important aroma component of aged beer
Beer
Beer is the world's most widely consumed andprobably oldest alcoholic beverage; it is the third most popular drink overall, after water and tea. It is produced by the brewing and fermentation of sugars, mainly derived from malted cereal grains, most commonly malted barley and malted wheat...

  and buckwheat
Buckwheat
Buckwheat refers to a variety of plants in the dicot family Polygonaceae: the Eurasian genus Fagopyrum, the North American genus Eriogonum, and the Northern Hemisphere genus Fallopia. Either of the latter two may be referred to as "wild buckwheat"...

. The odor of this substance is perceived as orris
Orris root
Orris root is a term used for the roots Iris germanica, Iris florentina, and Iris pallida. Once important in western herbal medicine, it is now used mainly as a fixative and base note in perfumery, as well as an ingredient in many brands of gin....

, fat
Fat
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...

 and cucumber
Cucumber
The cucumber is a widely cultivated plant in the gourd family Cucurbitaceae, which includes squash, and in the same genus as the muskmelon. The plant is a creeping vine which bears cylindrical edible fruit when ripe. There are three main varieties of cucumber: "slicing", "pickling", and...

.

In the April 2001 issue of the Journal of Investigative Dermatology
Journal of Investigative Dermatology
The Journal of Investigative Dermatology is a peer-reviewed scientific journal of dermatology published by the Nature Publishing Group. It is the highest impact factor journal in the category "Dermatology" for 2008, according to the Journal Citation Reports.-Indexing:The journal is indexed in:...

, Shinichiro Haze, et al. published an article entitled: "2-Nonenal, Newly Found in Human Body Odor Tends to Increase with Aging".

In this article they reported on their work which involved the analysis of body odor components collected via headspace gas chromatography/mass spectrometry, from shirts worn for three days by subjects between the ages of 26 and 75. They found that the concentration of many components of body odor were unaffected by age. They found that the concentration of 2-nonenal tended to increase with the age of the subjects, and determined that that 2-nonenal is generated by the oxidative degradation of omega-7 unsaturated fatty acids
Fatty acid
In chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually derived from...

, such as palmitoleic acid
Palmitoleic acid
Palmitoleic acid, or -9-hexadecenoic acid, is an omega-7 monounsaturated fatty acid with the formula CH35CH=CH7COOH that is a common constituent of the glycerides of human adipose tissue. It is present in all tissues, but generally found in higher concentrations in the liver...

 and vaccenic acid
Vaccenic acid
Vaccenic acid is an omega-7 fatty acid. It is a naturally occurring trans-fatty acid found in the fat of ruminants and in dairy products such as milk, butter, and yogurt. It is also the predominant fatty acid comprising trans fat in human milk....

, found on the skin surface.

They analyzed concentrations of various lipid
Lipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...

s on the skin surface by collecting samples in a gauze pad sewn into the shirts and then extracting the lipids with a hexane solvent. The article reported that concentrations of omega-10 fatty acids such as sapienic acid
Sapienic acid
Sapienic acid is a fatty acid that is a major component of human sebum. Among hair-bearing animals, sapienic acid is unique to humans . The equivalent fatty acid in mouse sebum is palmitoleic acid...

 showed no change with age. Concentrations of omega-7 fatty acids do increase with age.

Because of these findings, some observers have concluded that Haze's team has identified the cause of the phenomenon commonly known as "old lady smell", "old man smell" or "old person smell", a meme
Meme
A meme is "an idea, behaviour or style that spreads from person to person within a culture."A meme acts as a unit for carrying cultural ideas, symbols or practices, which can be transmitted from one mind to another through writing, speech, gestures, rituals or other imitable phenomena...

 found in pop culture
Popular culture
Popular culture is the totality of ideas, perspectives, attitudes, memes, images and other phenomena that are deemed preferred per an informal consensus within the mainstream of a given culture, especially Western culture of the early to mid 20th century and the emerging global mainstream of the...

relating to an odor that is characteristically associated with the elderly. Similarly, some consider 2-nonenal's odor to resemble that of old books and is at times casually referred to as "library aldehyde".
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