John Martin Behan

Production of malodorous steroids from androsta-5,16-dienes and androsta-4,16-dienes by Corynebacteria and other human axillary bacteria.

The biotransformations of a number of steroids, chiefly 5,6,16,17-tetradehydro-androstanes, are reported. The strains investigated were Corynebacteria sp. G38, G40, G41, B, Brevis sp. CW5 and Micrococcus sp. M-DH2. Corynebacterium sp. G41 proved remarkably efficient in effecting oxidative isomerisation of 5-ene-3-sterols into the corresponding 4-en-3-ones. The main biochemical reactions involved were oxidation at C-3; no reduction processes were observed. Conversions of 3beta-sterols into the C-3 oxo-steroids were high, but were correspondingly low for the 3alpha-sterol epimers. Androsta-4,16-dien-3-one and 5beta-androsta-16-en-3-one are crucial to the formation of malodour. The rate of formation of these compounds was measured over 72 h incubation periods using three substrates: androsta-5,16-dien-3beta-ol, androsta-4,16-dien-3beta-ol and androsta-5,16-dien-3-one. Induction studies of the transformation of the androsta-5,16-dien-3beta-ol into the very odorous compound androsta-4,16-dien-3-one showed that cells incubated with a mixture of antibiotics displayed the same extent of biotransformation as normal cells if the concentration of antibiotic was low (1, 3, 5 and 7 microg/ml), although at concentrations higher than 10 microg/ml, biotransformation yields were reduced. Pre-incubation with a 3beta-fluoro-steroid inhibited the formation of the odorous androsta-4,16-dien-3-one.

Insight into how skin changes perfume

Overall consumer perception of personal products such as colognes, deodorants, talc, and soap is often strongly influenced by the presence and nature of the fragrance incorporated into these products, which is also true for the corresponding olfactory characteristics of skin during and after application. Although extensive research has been carried out to define the morphology and characteristics of living skin, relatively little is known about the physical or (bio)chemical behaviour of perfume once deposited onto skin. It is widely acknowledged that some perfumes may perform very differently on different skins, but little definitive information is available to elucidate the associated mechanism(s). Rationalization of this may necessitate understanding both the physical and the chemical interactions between perfume and skin. To assist studies in this area, techniques based on headspace analysis and solvent swabbing have been developed to monitor fragrance concentrations on and above skin in use. Using these techniques, we have carried out some initial exploration into the physical and chemical interactions between skin and perfume. (a) Physical interactions: differences in perfume behaviour when on skin and when on a relatively inert surface (vitreous tile) were quantified to build up at least a qualitative idea of the importance of physical interactions between skin and perfume. (b) Chemical interactions: the potential for skin‐mediated chemical transformation of perfume was examined across a wide range of functional groups relevant to perfumes, but was found to be low under ‘non‐forcing’conditions (i.e. clean dry skin). However, some evidence has been found for changes in perfume ingredients in the underarm, probably arising from microbially catalysed reactions. It is envisaged that it may be possible to harness such transformations usefully – for example, to deliver unusual fragrance effects or enhance fragrance longevity. In addition, product‐mediated transformation on skin is feasible, and a specific case has been investigated based on the pH sensitivity of citral acetalization.