Identification of the Precursor of (S)-3-Methyl-3-sulfanylhexan-1-ol, the Sulfury Malodour of Human Axilla Sweat

Abstract

A careful study of human axillary microflora led us to the identification of a new strain of Staphylococcus haemolyticus. The role in axillary malodour formation of this microorganism was compared to those of Corynebacterium xerosis and Staphylococcus epidermidis, upon incubation on sterile human eccrine and apocrine axilla sweat. St. haemolyticus was responsible for the strongest sulfury malodour and the generation of the volatile sulfur compound (VSC) (S)-3-methyl-3-sulfanylhexan-1-ol (3). In this study, we investigated the nonvolatile precursors of VSCs. Human axillary sweat was collected, fractionated and analysed by HPLC/APCI-MS (High-Pressure Liquid Chromatography coupled to Atmospheric Pressure Chemical Ionisation Mass Spectrometry). The precursor of 3 was identified as [1-(2-hydroxyethyl)-1-methylbutyl]-L-cysteinylglycine (Cys-Gly-(S)-conjugate; 12). Because Cys-Gly-(S)-conjugates are key intermediates in the glutathione biodetoxification pathway, other derivatives of 12, specifically glutathione-(S)-conjugate 11 and Cys-(S)-conjugate 13, were prepared. Compounds 11 and 13 were not detected by HPLC/MS of sterile sweat. Synthetic homologues 11, 12, and 13 were incubated with C. xerosis, St. heamolyticus, and St. epidermidis. We observed efficient conversion of precursors 12 and 13 to form VSCs when incubated with St. haemolyticus, with a clear preference for 12. C. xerosis and St. epidermidis were less efficient in cleaving Cys-Gly-(S)-conjugate 12 to form the corresponding thiol 3. Incubation of glutathione-(S)-conjugate 11 never led to the formation of 3 under the experimental conditions employed.

The Sequential Action of a Dipeptidase and a β-Lyase Is Required for the Release of the Human Body Odorant 3-Methyl-3-sulfanylhexan-1-ol from a Secreted Cys-Gly-(S) Conjugate by Corynebacteria

“…We could detect cleavage of the Cys-Gly-(S) conjugate only in strains of Corynebacteria, which is in agreement with the well known fact that human subjects with a high population of Corynebacteria can form axillary malodor (2,25). However, Starkenmann et al (14) have reported that an isolate of S. haemeolyticus is releasing 3M3SH from the Cys-Gly-(S) conjugate. Thus, it appears that members of different bacterial genera present on axillary skin have adopted their enzymes to these secreted substrates.…”

“…However, the conjugate with the dipeptide Cys-Gly was later reported as the key precursor for 3M3SH (14). The presented LC-MS data now confirm the Cys-Gly-(S) conjugate as the major precursor of 3M3SH, but, in combination with the LC-MS 2 analysis, they clearly show that the Cys-(S) conjugate is also present, albeit at lower levels.…”

“…This compound can be released both from a Cys-(S) conjugate and from axilla secretions by a C-S lyase cloned from Corynebacterium Ax20, indicating that Cys-(S) conjugates could be physiological precursors for this compound class (12). However, it was later shown that a Cys-Gly-(S) conjugate of 3M3SH is secreted by human subjects (14) (for structures, see Fig. 1) and that bacterial cultures of Staphylococcus haemolyticus can release 3M3SH from * The costs of publication of this article were defrayed in part by the payment of page charges.…”

“…this dipeptide precursor. In a recent patent application, this activity was attributed to a ␤-lyase, but the corresponding enzyme was neither isolated from S. haemolyticus, nor has it been characterized (15). Thus, the enzymatic release of the key axilla odorant 3M3SH by skin bacteria from the physiological dipeptide precursor has not yet been deciphered.…”

Selective preconcentration of volatile mercaptans in small SPE cartridges: Quantitative determination of trace odor‐active polyfunctional mercaptans in wine

“…On the other hand, the most powerful aroma molecules in nature are polyfunctional mercaptans, which are molecules combining a second chemical functionality in the molecule. Most of such polyfunctional mercaptans have very strong and distinctive smells and are responsible for the aroma and flavor of numerous vegetable species, such as box, blackcurrant, grapefruit [4], passion fruit [5,6], onions [7,8] and green tea [9], of some foods such as coffee [10,11], meat [12][13][14], Iberian ham [15] and wine [16][17][18][19] and even have been described as majorly responsible for the odor of some species of mammals such as skunks [20], cats [21] or even humans [22]. There is an obvious need for analytical strategies not only for their quantitative determination, but also for their selective isolation.…”