Biochemistry of Human Axilla Malodor and Chemistry of Deodorant Ingredients

Abstract

Key human axilla malodorants are hexenoic acid (3) and 3-hydroxy-3-methyl-hexanoic acid (5), accompanied by some 25 structurally related hydroxyalkanoic acids and alkenoic acids. These sweat acids are secreted in the axilla in the form of odorless glutamine conjugates and are released upon enzymolysis by AMRE (Axillary Malodor Releasing Enzyme), produced by Corynebacteria. The sulfanylalkanols 8–11 represent another important group of axilla malodor compounds that are also secreted in the form of odorless precursors. The major precursors are cysteine–glycine sulfanylalkanol conjugates of type 14 and the minor precursors are cysteine sulfanylalkanol conjugates like 15. The release occurs upon action of a ?-lyase of axilla bacteria. Besides the classical approaches of axilla malodor masking using fragrances, the use of chemicals to neutralize malodorants is described. The elucidation of the biochemistry of the sweat acid release has allowed the development of fragrance precursors that act as competitive substrates to the natural malodor precursors as well as the development of specific antagonists that block AMRE. Finally, the characterization and functional expression of a first human malodor receptor presents an interesting approach for future development of axilla malodor blockers.

Profragrances and Properfumes

“…The structure elucidation of malodour precursors and the determination of their enzymatic degradation by skin bacteria are the key steps for the development of new deodorant strategies, either by developing efficient enzyme inhibitors or by preparing competitive substrates which release volatiles with a neutral or pleasant smell. 17 Based on the fact that the same Zn 2þ -dependent aminoacylase from Corynebacteria releases a variety of hexenoic acid derivatives, 16 Natsch and coworkers showed that the enzyme is indeed strongly selective to the L-glutamine residue but tolerates structural variations at the acyl part of the substrate. When fed to the Corynebacteria at the moment of the malodour formation, carbamate 5 releases 3-methyl-5-phenylpentanol (Phenoxanol) as Scheme 13.2 Generation of volatiles by bacterial enzymes on the skin a masking fragrance alcohol together with CO 2 and glutamine (Scheme 13.2).…”

Perfumes

“…However, the perfume industry has researched the origins of sweat odor for decades (eg, see Reference (19)) and identified a host of opportunities for creating perfumes and/or perfume additives that inhibit/counteract body odor quite effectively (20). For the APD sector, the need to perform well is particularly demanding, and clinical trials are often conducted to support claims.…”

“…Orris has a violet-like odor useful in fine perfumes, luxury soaps, and fragrances for powders and other cosmetic products. Its most important odor contributors are the irones, for example γ-irone (19) [79-68-5]. Orange Flower.…”

Controlled Release of Volatiles under Mild Reaction Conditions: From Nature to Everyday Products

“…Suitably designed fragrance precursors, which are cleaved by the malodor-creating enzyme to release neutral or pleasant odors, represent an interesting alternative to the use of antibacterial agents or enzyme inhibitors. [93] The cleavage of precursors by pyridoxal phosphate dependent amino acid b-lyases was reported to give a pyruvate, ammonia, and-depending on the substitution of the precursor-an alcohol, thiol, or carboxylic acid (Scheme 14 a). [94,95] The release of phenethylol (from 36) successfully reduced the formation of malodors from protein- containing secretions in a deodorant formulation.…”