trans-3-Methyl-2-hexenoic acid

trans-3-Methyl-2-hexenoic acid (TMHA) is an unsaturated short-chain fatty acid that occurs in sweat secreted by the axillary (underarm) apocrine glands of Caucasians and some Asians.[1]

trans-3-Methyl-2-hexenoic acid
Names
IUPAC name
(E)-3-Methylhex-2-enoic acid
Other names
E3M2H
3M2H
TMHA
MHA
C7:2 (Lipid numbers)
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.225.656
UNII
Properties
C7H12O2
Molar mass 128.171 g·mol−1
Density 0.97 g/cm3
Melting point −3.4 °C (25.9 °F; 269.8 K)
Boiling point 225.2 °C (437.4 °F; 498.3 K)
Hazards
Flash point 132 °C (270 °F; 405 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N (what is YN ?)
Infobox references

Hexanoic acids such as TMHA have a hircine odor. Of the fatty acids contributing to Caucasian men's underarm odor, TMHA has the most prominent odor.[2]

Schizophrenia odor

It has long been claimed that schizophrenia patients exhibit a particular peculiar body odor, and it has been postulated the odor may be caused by underlying metabolic abnormalities associated with the condition, among other factors.[3][4] Initial studies identified the causal component as TMHA,[5] however, subsequent studies failed to reproduce such results,[3][6] with subsequent researchers suggesting the initial research may have had misidentified impurities in samples as TMHA due to poor methodology.[3] However, a 2007 study found schizophrenia patients to have reduced olfactory sensitivity to TMHA, possibly indicating sensory habituation; the decreased ability to smell the substance due to the presence of the substance as a constant component of subjects' own sweat and body odor. Furthermore, the researchers noted a positive association between reduced ability to smell TMHA and greater severity of disorganised and negative symptoms.[4]

An allusion to TMHA and its purported link to the smell of the mentally ill is made in the 1996 David Foster Wallace novel, Infinite Jest,[7] and in the 1988 novel The Silence of the Lambs by Thomas Harris.

References
  1. Akutsu, T.; Sekiguchi, K; Ohmori, T; Sakurada, K (2006). "Individual Comparisons of the Levels of (E)-3-Methyl-2-Hexenoic Acid, an Axillary Odor–Related Compound, in Japanese". Chemical Senses. 31 (6): 557–63. doi:10.1093/chemse/bjj060. PMID 16690870.
  2. Sun, Lixing; Williams, Wendy A.; Avalos, Corinna (2005). Human sweaty smell does not affect women's menstrual cycle. pp. 308–312. doi:10.1007/0-387-25160-X_34. ISBN 978-0-387-25159-2.
  3. Perry, Thomas L.; Melançon, Serge B.; Lesk, Donna; Hansen, Shirley (December 1970). "Failure to detect trans-3-methyl-2-hexenoic acid in the sweat of schizophrenic patients". Clinica Chimica Acta. 30 (3): 721–725. doi:10.1016/0009-8981(70)90266-4. ISSN 0009-8981. PMID 5493894.
  4. Brewer, Warrick J.; Wood, Stephen J.; Pantelis, Christos; Berger, Gregor E.; Copolov, David L.; McGorry, Patrick D. (January 2007). "Olfactory sensitivity through the course of psychosis: Relationships to olfactory identification, symptomatology and the schizophrenia odour". Psychiatry Research. 149 (1–3): 97–104. doi:10.1016/j.psychres.2006.03.005. ISSN 0165-1781. PMID 17156856. S2CID 37511465.
  5. Smith, K.; Thompson, G. F.; Koster, H. D. (1969-10-17). "Sweat in schizophrenic patients: identification of the odorous substance". Science. 166 (3903): 398–399. Bibcode:1969Sci...166..398S. doi:10.1126/science.166.3903.398. ISSN 0036-8075. PMID 5818039. S2CID 21377002.
  6. Gordon, S. G.; Smith, K.; Rabinowitz, J. L.; Vagelos, P. R. (July 1973). "Studies of trans-3-methyl-2-hexenoic acid in normal and schizophrenic humans". Journal of Lipid Research. 14 (4): 495–503. ISSN 0022-2275. PMID 4715330.
  7. Foster., Wallace, David (1996). Infinite jest : a novel (1st ed.). Boston: Little, Brown and Co. pp. 748–749. ISBN 9780316073851. OCLC 669069481.
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