Patent Publication Number: US-4220665-A

Title: Bacteriostatic composition and method

Description:
The present invention relates to a bacteriostatic composition and method of combating growth of certain Gram-positive skin bacteria. 
     A large number of various bacteria settle on the human skin. These are mostly non-pathogenic and do not affect skin condition or odor. Others, by their presence, on the other hand, prevent penetration of pathogenic bacteria which cause disease of portions of the skin. The degeneration of normally substantially odorless or weakly smelling substances contained in perspiration by the bacterial flora of the skin, leads to formation of products having an unpleasant odor which can be of considerable discomfort to the person affected. 
     For the purpose of removing such products having an unpleasant odor, or for the purpose of preventing their formation, cosmetic preparations are employed which either reduce perspiration at the skin surface (antiperspirant) or which substantially destroy the natural bacterial flora of the skin (bacteriocidal deodorants). In both cases significant disruptions of natural conditions at the skin surface occur. The deodorants which are of particular interest here practically always comprise strongly halogenated phenol compounds, the use of which is according to most recent knowledge not necessarily without problem, and in view of their strong bacteriocidal activity destroy practically all bacterial skin flora. 
     Products are therefore being sought which prevent or strongly diminish growth of bacterial flora of the skin, which are present also after conventional bathing, which products however do not further disturb the natural equilibrium of biological procedures at the surface of the skin. 
     It has now been found that the substance farnesol (3,7,11-trimethyl-dodeca-2,6,10-trien-1-ol) which occurs widely in nature, is higly effective in inhibiting the growth of odor-forming bacterial flora of the skin at relatively low concentrations, without influencing the biological equilibrium at the skin surface. 
     The invention accordingly relates to the use of farnesol as a bacteriostatic agent, or a component thereof, in cosmetic products for application to the human skin. 
     Although farnesol has long been known to be present in ether oils, and experimentation has been carried out on the bacteriostatic or bacteriocidal activity of such ether oils, the bacteriostatic activity of the natural substance farnesol has remained unrecognized. This is no doubt to be attributed to the fact that farnesol is normally present in the ether oils in extremely low amounts and that the concentration, at which a bacteriostatic activity is exhibited, has not been reached. 
     It has been found that at a concentration of more than 0.15% by weight of farnesol, calculated on the total weight of the composition or cosmetic product, a significant bacteriostatic activity is exhibited. At a concentration of 0.3% by weight of farnesol, a complete inhibition of the odor-forming Gram-positive bacteria Staphylococcus aureus and Staphylococcus epidermidis as well as an effective inhibition of Coryne-bacterium spec. takes place. Here, the sensitivity to farnesol of the pathogenic Staphylococcus (Staph. aureus) is greater than the epidermal Staphylococcus (Staph. epidermidis). The growth of pathogenic Staphylococcus is completely inhibited at a concentration of 0.2% farnesol. Growth of gram-negative bacteria and yeasts is not inhibited by farnesol. A definite fall in activity of farnesol is observed at a concentration of 0.15% so that this is the lower concentration limit for useful products, at least for products to be employed for achieving incomplete inhibition. 
     For cosmetic preparations, a farnesol concentration of 0.25% is sufficient in all circumstances. The minimum inhibition concentration to achieve a total inhibition of growth of the odor-forming Gram-positive bacteria to be observed is 0.3%, whereby it is however to be noted that a total inhibition is not in all circumstances desirable. All percentage contents which are here given are percentum by weight. 
     Important for the usefulness of farnesol as a bacteriostatic in the cosmetic field is the duration of action in practical application, the so-called depot effect. This activity was tested with the aid of a &#34;contact growth index method&#34;, in which pieces of filter paper are treated with 0.2 ml of an alcoholic solution of corresponding concentration, dried and then exposed for different time periods to a medium having a 90% relative humidity at 37° C. These pre-treated samples were then tested for their contact growth index with Staphylococcus aureus and Staphylococcus epidermidis as well as Corynebacterium spec. These tests show that a cosmetically significant depot effect is definitely present for a period of 6 hours, which is in practice adequate for deodorant remanence. 
     Since farnesol can also be employed as a component of perfume compositions, such compositions having a correspondingly high content of farnesol were tested for their bacteriostatic activity. The activity of such farnesol-rich perfume compositions could similarly be clearly shown. Antagonistic effects due to the presence of other components of the perfume composition could not be determined. Since the amount of perfume in cosmetic finished products is normally from about 0.5 to about 1%, a perfume or perfume oil which comprises farnesol as active bacteriostatic must consist of from about 30 to about 60% farnesol. Farnesol as a sesquiterpene alcohol possesses only a relatively weak smell, but has good fixative properties and can thus be employed without reservation in high concentrations as a component of perfume compositions. 
     The following Tables provide a survey of the microbiological test results obtained with farnesol as substance and with perfume compositions containing farnesol. The same perfume compositions, without farnesol, show practically no inhibition in the test. 
     
                                           Table 1                                 
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Results of the contact growth index test of farnesol as against different 
types                                                                     
of micro-organisms at different concentrations.                           
                       Contact Growth Index Against                       
                       Staph.  Coryne-                                    
                       aureus                                             
                           Staph.                                         
                               bact.                                      
                                    E. Aerob.                             
                                           Pseud.                         
                                               Candi                      
Formulation                                                               
       Concentration                                                      
               Application                                                
                       SG 511                                             
                           epid.                                          
                               spec.                                      
                                    colli                                 
                                       Klebs.                             
                                           pyoc.                          
                                               albio                      
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Farnesol                                                                  
       0.3%    0.2 ml/15.9 cm.sup.2                                       
                       0   0   1    4  4   4   4                          
&#34;      0.25%   &#34;       0   1   1-2  4  4   4   4                          
&#34;      0.2%    &#34;       0   1-2 2-3  4  4   4   4                          
&#34;      0.15%   &#34;       3   3-4 4    4  4   4   4                          
&#34;      0.1%    &#34;       3-4 4   4    4  4   4   4                          
96% Ethyl-                                                                
alcohol                                                                   
       conc.   &#34;       4   4   4    4  4   4   4                          
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                                           Table 2                                 
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Results of the contact growth index test at o.3% concentration of         
farnesol after                                                            
physical treatment by temperature and increased humidity after different  
times.                                                                    
                         Contact growth                                   
                         index of                                         
                         coated plates                                    
                         left at 37° C.                            
                         and 90% relative                                 
                         humidity after                                   
Formulation                                                               
        Application                                                       
                Bacteria type                                             
                         1 2 4 6  12                                      
                                    24 hours                              
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Farnesol o.3%                                                             
        0.2 ml/15.9 cm.sup.2                                              
                 Staph. aureus                                            
                SG 511   0 0 0 0-1                                        
                                  4 4                                     
&#34;       &#34;       Staph. epiderm.                                           
                         0 0 0 0-1                                        
                                  4 4                                     
&#34;       &#34;       Corynebact. spec.                                         
                         0 0 0 2-3                                        
                                  4 4                                     
96% Ethyl-                                                                
alcohol &#34;       Staph. aureus                                             
                SG 511                                                    
                Staph. epid.                                              
                         4 4 4 4  4 4                                     
                Corynebact. spec.                                         
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                       Table 3                                                     
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Results of the contact growth index test of different                     
formulations in 0.6% alcohol solution against                             
Staphylococcus epidermidisand Corynebacterium spec.                       
Perfume oils were mixed at a 1:1 ratio with                               
farnesol and tested in parallel with the perfume -without farnesol.       
           Concen-  Appli-  Staphyloc.                                    
                                    Coryne-                               
Perfume oil                                                               
           tration  cation  epidermidis                                   
                                    bact.                                 
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                    0.2 ml/                                               
DR 9195-1/50%                                                             
           0.6%     15.9 cm.sup.2                                         
                            0       0                                     
Farnesol            0.2 ml/                                               
DR 0/9230/50%                                                             
           0.6%     15.9 cm.sup.2                                         
                            0       1                                     
Farnesol            0.2 ml/                                               
DR 0/9195/50%                                                             
           0.6%     15.9 cm.sup.2                                         
Farnesol            0.2 ml/                                               
DR 0/9279/50%                                                             
           0.6%     15.9 cm.sup.2                                         
                            0       0                                     
Farnesol            0.2 ml/                                               
DR 9195-1  0.6%     15.9 cm.sup.2                                         
                            3-4     4                                     
                    0.2 ml/                                               
DR 0/9230  0.6%     15.9 cm.sup.2                                         
                            4       4                                     
                    0.2 ml/                                               
DR 0/9195  0.6%     15.9 cm.sup.2                                         
                            4       4                                     
                    0.2 ml/                                               
DR 0/9279  0.6%     15.9 cm.sup.2                                         
                            4       4                                     
                    0.2 ml/                                               
Deodorant Spray                                                           
           0.6%     15.9 cm.sup.2                                         
                            4       4                                     
Lavender            0.2 ml/                                               
Ethyl alcohol                                                             
           96.0%    15.9 cm.sup.2                                         
                            4       4                                     
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 Note: The above numbers are employed to identify perfume oils the base   
 composition of which is shown on pages 10 to 13.                         
 
    
     It can be seen from above that a content of at least 0.15% by weight of farnesol in cosmetic products leads to a good bacteriostatic activity on Gram-positive epidermal bacterial flora. A content of at least 0.2% leads to a complete inhibition of the growth of pathogenic Staphylococcus and is sufficient for many purposes, for example for deodorants where a content of 0.2 to 0.5% farnesol is suitable. 
     Where demands are greater, the lower concentration limit is 0.25% farnesol and for cosmetic products with which a substantially complete or complete inhibition of growth of Gram-positive bacteria should be obtained, farnesol should be present at a concentration of 0.3% or more. For practical reasons, at most 1% farnesol would be included in cosmetic products, although basically there is no upper limit. 
     
         ______________________________________                                    
DR 9195-1                                                                 
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60 g       Phenyl Ethyl Alcohol                                           
50 g       Bencyl Acetate                                                 
350 g      Hexyl Cinnamic Aldehyde alpha                                  
280 g      Hydroxy citronellal                                            
120 g      Bergamott Oil                                                  
50 g       Lemon Oil                                                      
30 g       Citronellol                                                    
40 g       Lavandin Oil                                                   
40 g       Styrallyl Acetate                                              
20 g       Lyral                                                          
40 g       Galaxolide                                                     
20 g       Linalyl Acetate                                                
20 g       Linalool                                                       
20 g       Rhodinol                                                       
20 g       Phenyl ethyl dimethyl carbinol                                 
20 g       Bencyl Salicylate                                              
20 g       Nerolidol                                                      
1200 g                                                                    
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         ______________________________________                                    
DR 9230                                                                   
______________________________________                                    
100 g            Litsea Cubeba Oil                                        
140 g            Bergamott Oil                                            
40 g             Galbanum Oil                                             
140 g            Lemon Oil                                                
60 g             Methyl Ionone                                            
120 g            Vetikone                                                 
40 g             Ylang Ylang Oil                                          
40 g             Coumarin                                                 
50 g             Phenyl Ethyl Alcohol                                     
20 g             Styralyl Acetate                                         
40 g             Sauge Sclaree                                            
10 g             Storax Resinoid                                          
40 g             Peppermint Oil                                           
40 g             Menthanyl Acetate                                        
10 g             Aldehyde C 12 MNA                                        
60 g             Dimyrcetol                                               
10 g             Macis Oil                                                
40 g             Citronellyl Nitrile                                      
1000 g                                                                    
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         ______________________________________                                    
DR 9195                                                                   
______________________________________                                    
160 g        Hydroxy citronellal                                          
120 g        Phenyl Ethyl Alcohol                                         
200 g        Hexyl Cinnamic Aldehyde alpha                                
100 g        Bencyl Acetate                                               
40 g         Ylang Ylang Oil                                              
40 g         Lyral                                                        
50 g         Lilial                                                       
60 g         Patchouly Oil                                                
80 g         Galaxolide                                                   
40 g         Isoeugenol                                                   
40 g         Labdanum Extract                                             
20 g         Coumarin                                                     
40 g         Linalool                                                     
10 g         Isobutyl chinoline                                           
1000 g                                                                    
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         ______________________________________                                    
DR 9279                                                                   
______________________________________                                    
200 g        Diheptyl Acetate                                             
80 g         Bencyl Acetate                                               
90 g         Amyl Cinnamic Aldehyde alpha                                 
90 g         Lilial                                                       
30 g         Amyl Salicylate                                              
60 g         Hydroxycitronellal                                           
30 g         Ylang Ylang Oil                                              
60 g         Cedren Epoxide                                               
20 g         Coumarin                                                     
50 g         Terpineol                                                    
90 g         Bergamott Oil                                                
50 g         Petitgrain Oil                                               
50 g         Eucalyptus Oil                                               
80 g         Orange Oil                                                   
40 g         Dimyrcetol                                                   
180 g        Phenyl Ethyl Alcohol                                         
1200 g                                                                    
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