3-Hydroxy-3-methylhexanoic acid (1) and the 3-sulfanylalkan-1-ols 2-5 were identified to contribute to the odor of human axillary sweat. Quantitative analyses of axillary sweat extracts from 50 healthy men showed an unambiguous correlation between the detected levels of 1 and the intensity of the axillary odor. Chiral-GC analyses revealed 1 to be a 72:28 mixture of the (S)/(R)-isomers. Optically pure (S)-1 (>97% ee) emanated a strong spicy note, which recalled typical axillary odors. 3-Methyl-3-sulfanylhexan-1-ol (2), the enantiomeric ratio of which equaled that of 1, was present in greater quantity than any of the other 3-sulfanylalkanols. Optically pure (S)-2 (>97% ee) had a strong meaty, fruity note, also reminiscent of axillary odor. The compounds identified, in particular (S)-1 and (S)-2, contribute significantly to the olfactory impression of human axillary odor.

3-Hydroxy-3-methylhexanoic acid (1) and the 3-sulfanylalkan-1-ols 2 ± 5 were identified to contribute to the odor of human axillary sweat. Quantitative analyses of axillary sweat extracts from 50 healthy men showed an unambiguous correlation between the detected levels of 1 and the intensity of the axillary odor. Chiral-GC analyses revealed 1 to be a 72 : 28 mixture of the (S)/(R)-isomers. Optically pure (S)-1 (> 97% ee) emanated a strong spicy note, which recalled typical axillary odors. 3-Methyl-3-sulfanylhexan-1-ol (2), the enantiomeric ratio of which equaled that of 1, was present in greater quantity than any of the other 3-sulfanylalkanols. Optically pure (S)-2 (> 97% ee) had a strong meaty, fruity note, also reminiscent of axillary odor. The compounds identified, in particular (S)-1 and (S)-2, contribute significantly to the olfactory impression of human axillary odor.Introduction. ± The human body generates a variety of different odors. Scalp, hair, mouth, axillae, foot, and even the general skin surface all possess characteristic odors that are formed by septic action due to bacterial degradation. Of all the human scents, axillary odor is probably the most powerful and impressive. The axillary odor has been examined and discussed from an analytical, biological, and behavioral-physiology point of view. In particular, there is a wealth of information suggesting that it may contain chemical signals that affect the menstrual cycle [1] or may be involved in mate selection depending on a major-histocompatibility-complex (MHC) allele [2]. There are also several reports on actual axillary odorants [3], of which (E)-3-methylhex-2-enoic acid (3M2 H; see below) is considered one of the most important. 3M2 H was first reported by Zen and co-workers in 1991 [3d], who analyzed axillary odors collected from Americans, and, since then, researchers have mainly focused on this unsaturated acid. However, our own experiments have established that 3M2 H is not solely responsible for axillary odors. After a thorough analysis of the chemical composition of axillary odor, we discovered two new constituents, which also contribute significantly to the overall odor. One of them possesses a spicy note, while the other has a sulfury odor.Results and Discussion. ± 1. Analysis of the Spicy Constituent. A total of 50 healthy Japanese male volunteers were asked to collect their underarm odors by wearing clean white T-shirts that had fully defatted cotton inserts stitched into both of the armpit positions. Each insert was evaluated: 20% of the volunteers showed typical axillary odors, and 80% had a sour, acidic odor. The inserts were extracted with diethyl ether, and the ethereal extracts were treated with base. As this made the strong distinctive spicy odor disappear, the characteristic axillary odor was apparently caused by acidic

In our daily lives we are confronted with various kinds of malodour problems. Detailed analysis at the molecular level of the malodorous constituents with gas chromatography–mass spectrometry and gas chromatography–olfactometry can be used to identify the key chemicals responsible for the malodours, and such information can provide novel starting points for the development of new deodorants. This paper describes two characteristic sources of malodour in daily life: axillary and laundry malodour. Detailed analytical studies identified specific major contributors to these malodours: 3‐hydroxy‐3‐methylhexanoic acid, 3‐mercapto‐3‐methylhexan‐1‐ol and 4‐methyl‐3‐hexenoic acid. Biochemical and microbiological studies then elucidated the mechanisms generating these odours and proved the involvement of microbes in odour formation. In this review, we discuss the importance of the branched C7 chain, which is common to all the major volatile substances identified in these studies and perceived by the human nose with an extraordinary sensitivity. Copyright © 2012 John Wiley & Sons, Ltd.

An in vitro system was developed to mimic the structural and flow conditions of the human olfactory epithelium and to measure the dynamics of odorantbinding to odor-binding protein (OBP). A hydrophilic fused silica capillary, coated internally with a thin (about 1.3 µm) aqueous film of recombinant rat-OBP3 mimicked the human olfactory epithelium. Isobutylthiazole in air was introduced into the capillary, and the outflow gas was monitored in real-time using on-line mass spectrometry. Time-dependent changes in the gas phase odorant concentration gave an indication of the rate and extent of mass transfer between the gas phase and the aqueous OBP layer during the initial uptake phase, during the steady state (when the OBP was fully loaded with odorant) and then during a release phase when clean air was introduced into the capillary. Control experiments showed no significant isobutylthiazole interaction with the system and measured the contribution of water to odorant uptake. Isobutylthiazole uptake was then measured under different flow and concentration regimes, from which the stoichiometry of binding was calculated. The measured flow and structural characteristics in the model system were comparable with the situation in vivo. Uptake and release of isobutylthiazole with OBP3 during a simulated tidal flow regime showed strong uptake but little release of odorant due to the strong binding characteristics of this particular compound. The model system (dynamic biomimetic odorant-binding system) allowed monitoring of the dynamic binding and release of airborne odorants to OBP, and the resulting kinetic data provide an insight into the way OBP functions in vivo.