Patent Publication Number: US-4370315-A

Title: Post-depilatory composition reducing progressively the growth of body hair

Description:
This invention concerns a new way of extending the duration of depilation carried out with classical methods, such as complete extraction of body hair on humans and living animals with the help of depilatory nipper, wax or paste. In this case, it takes about 2 or 3 weeks before new hair appears. This makes frequent renewal of the depilation procedure necessary. Furthermore, these operations are very irritating for the skin, and other soothing and softening preparations are needed. 
     The said invention concerns a new process of extending the action of depilation by reducing noticeably the fresh growth of hair. 
     From Kantorowicz&#39;s observations made in 1907 (German Pat. No. 196 617), it was shown that some metallic peroxides and peroxidized anions delayed the growth of body hair. In the same objective, the authors of the present invention have noticed more precise facts, and proposed new means without the disadvantages of the peroxidized compounds cited hereabove. 
     The invented process consists in incorporating enzymes with their substrate into the preparation. These enzymes are lipoxygenases, extracted from soya beans (G. Hispida), classified: EC 1.13.11.12 [1]. They are commercially available under the name of lipoxydase. Lipoxygenases of different vegetal origin could be used as well. 
     The substrate used is linoleic acid, also called vitamin F acid. Its derivatives, such as methyl-, ethyl-, glyceric esters. diethanolamide or its metallic soaps (sodium or potassium) can also be used as substrate, in the same way as α linolenic or γ linolenic acids. One remarks that linoleic acid is normally present in fatty acids of the human skin, at about 0.65% for a healthy skin [2]. 
     The preparations which incorporate these substances are ointments, creams, milks, lotions and generally any cosmetics preparation either fluid or not. The dosage is 250,000 to 1,000,000 enzymatic activity units [3] for 100 grams of end-product. The substrate represents 0.5 to 2% w/w. The preparation may also contain classical substances which are interesting for the above-mentioned use. 
    
    
     For example, the following formula can be used for a lotion: 
     
         ______________________________________                                    
Tegin [4]            2.500                                                
Cetiol HE [5]        0.200                                                
P.E.G. 400           3.500                                                
Water                90.290                                               
Titanium dioxyde     1.000                                                
Propylene glycol     0.800                                                
Preservative         0.300                                                
Linoleic acid        1.000                                                
Lipoxidase           0.010                                                
Menthol              0.100                                                
Fragrance            0.300                                                
Polysorbate 20       0.500                                                
Sodium borate        q.s.p. pH 8.0                                        
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     The lipoxygenases used had an activity of 48,000 A.U./mg. One can of course use batches with other specific activities by changing proportionally the amount of enzymes. 
     This lotion was used by 20 female volunteers, aged 20 to 35, after depilation of certain body parts (legs, arms, under-arms). The lotion is uniformly and quickly spread over the depilated parts, using 1 g. per 50 sq. cm, by slight massages. The absorption is fast and leaves no greasy film; the depilation can then be renewed either on an adjoining region or on the same spot, if the first operation was insufficient. 
     No subject experienced irritation, not even on normally sensitive parts (under-arms, internal surface of legs). A feeling of freshness was noted every time. 
     On 16 cases, i.e. 80%, fresh growth of hair was clearly perceptible only 6 or more weeks later. Volunteers using this preparation for several and successive depilations at the same parts noted that hair growth was delayed progressively up to 2 months. Moreover, they noticed a decreasing density of hair. 
     All these volunteers had used classical commercial preparations in the past. Under these conditions, the regrowth of hair was complete after 3 weeks at the latest. 
     The products obtained by reaction of lipoxygenases on the above-mentioned substrates are their hydroperoxides. When the substrate is linoleic acid, the principal product is 13-L-hydroperoxy-cis, trans-9, 11-octadecadienoic acid [6], under the physical conditions of manufacture and use of these preparations: moderately alkaline medium (8≦pH≦9), ambient temperature and exposure to the air. 
     Another achievement of this invention is the fact that the hydroperoxides of linoleic or linolenic acids, previously synthesized by chemical or biological ways, then purified, can be incorporated directly into cosmetic preparations. 
     It has been shown that the peroxides of linoleic acid considerably change the ionic conductivity of phospholipidic membranes in alkaline medium [7]. We suggest that the observed effect is related to this increased membrane conductivity, particularly to the bottom of the follicle where the metabolism leading to the growth of the hair takes place. 
     REFERENCES 
     [1] Enzyme Nomenclature, Recommendations (1972) of the IUPAC-IUB, p. 104, American Elsevier Pub. Co., New York, NY, (1973). 
     [2] Krakow R., Downing D. T., Strauss J. S., and Pochi P. E., J. Invest. Dermatol., 61, 286 (1973). 
     [3] Enzyme Nomenclature, Recommendations (1972) of the IUPAC-IUB, p. 26, ibid. 
     [4] Trade mark of Theodor Goldschmidt AG, Essen, W. Germany. 
     [5] Trade mark of Henkel GmbH, Du sseldorf, W. Germany. 
     [6] Leu K., Lebensm.-Wiss. Technol., 7, 82 (1974). 
     [7] Antonov V. F., Vladimirov Yu. A., Rossel&#39;s A. N., Korkina L. G., Korepanova Ye. A. and Trukhmanova K. I., Biofizika, 18, 668 (1973).