j. Soc. Cosmet. Chem., 44, 211-220 (July/August 1993) Growth inhibition of coryneform bacteria by a mixture of three natural products Farnesol, glyceryl monolaurate, and phenoxyethanol' HGQ U.-F. HAUSTEIN, J. HERRMANN, U. HOPPE, W. ENGEL, and G. SAUERMANN, Department of Skin Diseases, University of Leipzig (U.-F. H., J. H. ), and the Paul Gerson Unna Research Center, Beiersdorf AG, Hamburg (U. H., W. E,, G. S.), Germany. Received January 11, 1993. Synopsis Axillary realodor is produced by secretions of the apocrine sweat glands that are contaminated by coryne- form bacteria. One of the mechanisms of deodorant action is to inhibit bacterial growth. This investigation was designed to study the bactericidal effect of the mixture of three natural products, HGQ,* on wild strains of axillary coryneform bacteria. Thirty corynebacteria species could be isolated and identified biochemically from 530 underarm swabs. Their sensitivity to the HGQ mixture was determined by means of the minimum bactericidal concentration. It ranged from 0.025% to 1% HGQ. 47% of the strains were inhibited by less than 0.1% HGQ, 30% by less than 0.3%, and 23% by less than 1.0% HGQ. The sensitivity to HGQ did not correlate with specific corynebacteria strains but with the survival time of the strains, i.e., the most sensitive strains had the shortest survival times at 4øC, both on blood agar and in the stab culture. Our studies show that HGQ, a mixture composed of three products occurring in plant or animal species, farnesot, gtyceryl monolaurate, and phenoxyethanol, kills corynebacteria and that it can be recommended for use as an effective deodorant, as has already been confirmed by its successful use in practice. HGQ and its components are biologically degradable to more than 60% within 28 days. Only CO 2 and H20 are formed, since there is no nitrogen contained in HGQ. Furthermore, this finding indicates that although the synergistically acting HGQ mixture has a selective bactericidal effect, it is degraded naturally after use, which is not true of the first generation of deodorants. INTRODUCTION The underarms play an important role in the generation of body odor. Odor is generated here from secretions of the apocrine sweat glands, which are primarily contaminated by coryneform bacteria (20). C3-fatty acids, (iso)butyric acid, isovaleric acid, and androgen steroids such as I6, 5-0-androsten-3•-ol and 16,5-0-androsten-3-1 have been identified as the odorous substances. The latter are excreted in odorless axillary sweat as water- * Farnesot Plus ©, Dragoco Gerberding & Co. GmbH, D-3450 Holzminden, Germany. 211

212 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS soluble sulfates or glucuronides and then liberated by hydrolytic enzymes of bacteria and/or the skin as volatile steroids. A gas chromatographic analysis of axillary sweat, performed parallel to a sniff test with perfumers, gave 20 different odorous substances. A few by these substances characterized only by retention times occurred in all persons studied (2). Moreover, amino acids with a characteristic odor have been identified in eccrine sweat (15). Sweat secretion, the bacteria population, and a moist environment are the three major components contributing to odor production by the skin (4,6,14,21,22). The bacteria flora of the skin vary within broad limits both qualitatively and quantitatively (5,14). In a review, the relationships between the bacteria population, the host, and the environment have already been described (7). From the foregoing it becomes understandable why it is possible to inhibit sweat odor by different mechanisms. These include: ß inhibition of sweat secretion by systemic administration of sedatives, ataractics, parasympatholytics, and saluretics ß application of topical antiperspirants, such as formaldehyde, glutaraldehyde (danger of sensitization), and formulations containing aluminum hydroxycholoride and tan- nins ß binding of odorous substances by mixtures of zinc ricinoleate and other zinc com- pounds that act synergistically (17) ß environmental control, e.g., by body hygiene (soap or surfactants), and by absorbent, loose underwear ß deodorizing by means of an antibacterial therapy with strong disinfectants such as halogenated phenol compounds or quarternary ammonium compounds that influence virtually all of skin flora in the same way (12) Inhibition of esterases is an alternative mechanism of deodorant action. Glyceryl triace- tate, triethyl citrate, and other rapidly saponifying esters represent substances acting according to this mechanism. However, most other esters are bacteriologically inert, i.e., have no measurable antibacterial effect, when tested according to conventional methods. The aryl sulfatases and [3-glucuronidases can also be inhibited by Cu + +- and Zn + + compounds. For example, even concentrations of 10-100 •x Cu or zinc glycinate have an effect (3). If proliferation of bacteria is prevented by antimicrobial substances, the production of skin odor caused by bacterial decomposition of sweat is also largely reduced. However, it is still possible that the deodorant effect could be a result of a regulatory role of the substance in the biochemical processes on the skin surface. For years the deodorant HGQ, which is recommended as a natural synergistic complex of active substances (9), has proved successful in everyday use. It is offered as a con- centrate as well as a 50% solution in dipropylene glycol or ethanol, and consists of three individual components: ß 34% farnesol, which has been identified in cotton bud oil, cabreuva oil, musk seed oil, neroli oil, tuberose blossom oil and other volatile oils ß 11% glyceryl monolaurate, found in the feather fat or marabous (Leptoptilos cru- meniferus) ß 53% phenoxyethanol, which occurs in tropical fruits, in Cichorium endivia and in Camellia sinensis (green tea)