310 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS higher concentrations of glycerol triacetate or to become resistant to the glyceride. All attempts to induce resistance of the fungi to 0.1 per cent glycerol triacetate have failed in fact, often the first colony on medium containing the glyceride is about 10 per cent larger than subsequent colonies derived from the first. Likewise attempts to induce resistance by the gradient plate procedure have been negative. It is apparent t•om these tests that triacetin certainly is not in the antibiotic class in regard to its effective concentration in laboratory tests but clinically results have been most gratifying. Here again, as many have noted in the past, there seems to be no constant relationship between in vitro and in vivo activity. TABLE 2.--TI•E EFFECT OF BLOOD SERUM ON THE FUNGISTATIC ACTIVITY OF 0.1 PER C•NT TRIACETIN Fungus TABLE 3.--MILLILITERS N/10 ACETIC ACXD PRODUCED BY ESTERASES FROM DERMATOPHYTES AND SERUM Diameter of Colony N/10 Acetic in mm. Acid Serum Added, Released in •----Per Cent------- ml. 0 1 5 10 Source of Esterase pH 6.5 pH 4.0 Epidermophyton Microsporum audouini 15.6 O . 4 floccosum 22 8 0 0 Trichophyton mentagrophytes 7.3 3.0 Trichophyton Trichophyton rubrum 6 8 O. 7 mentagrophytes 70 63 47 32 Serum, 5% 4.9 5.6 Microsporum Medium t¾om Microsporum audouini 49 21 18 13 audouini culture 12.2 0.2 Candida albicans 19 24 17 14 Boiled serum and fungi (control) 0 0 'Fable 2 shows the effect of blood serum on the fungistatic effect of 0.1 per cent triacetin. The extent of inhibition obtained in the presence of serum is the net result of opposing forces: the stimulatory effect of serum components on the fungus, the inhibitory effect caused by the increased acetic acid released by serum esterase and the inactivation, if any, of the serum on either acetic acid or triacetin. It is apparent that the inhibition caused by the increased acetic acid released by serum esterase was the dominant force. When triacetin and aliquots of serum were incubated together for twenty-four hours before addition to the test medium the results were the same, indicating that serum probably does not bind or otherwise make the triglycefide unavailable for hydrolysis. Table 3 shows that at least some of the superficial dermatophytes as well as blood serum contain esterase capable of releasing acetic acid from tri- acetin. Here again the fungi should not be compared, because no attempt was made to use the same number of cells or mass of tissue in each test. It is interesting to note that this strain of 3Iicrosporum audouini excretes considerable esterase into the medium in which it is growing if this were to occur in the infection also, the breakdown of epidermal lipids might play a part in the overall infectious process. It is noteworthy also that Candida

THERAPEUTIC POTENTIALITIES OF TRIGLYCERIDES 311 albicaus has relatively little of this particular esterase, this may account in part for the ineffectiveness of triacetin formulations in treating superficial candidiasis plus the fact that the yeast is not quite so sensitive to fatty acids as the truly filamentous fungi. The effect of pH on the hydrolysis of triacetin by esterases of various origin is shown in Table 4. In general the esterases have a rather broad TABLE 4.--THE EFFECT OF pH ON THE HYDROLYSIS OF TRIACETIN BY ESTERASES OF DERMATOPHYTES, SERUM AND SKIN • N/10 Acetic Acid Produced in 18 Hr. T. rubrum, T. menta- M. audouini, Serum, ml., pH ml. grophytes, ml. ml. Skin, ml. 35 0.3 0.4 0 4.0 1.0 4.1 0.6 4.5 2.8 1.9 5.0 3.3 •i• 4.6 5.5 3.9 3.8 6.2 6.0 4.4 4.0 11.7 6.5 5.1 5.0 12.2 7,0 7.8 3.8 12.0 7.5 10.8 5.7 12.5 8.0 9.4 4.7 9.1 32 65 80 83 76 56 3.4 3.3 4.5 5.0 0 1.3 2.4 4.0 5.6 7.8 7.4 7.6 7.0 7.0 plateau of maximum activity with rapidly decreasing activity in the region of pH 3.5 to 4.0. Note the eighteen-hour reaction time these esterases seem to have rather low turnover rates, or the conditions for testing were not optimum. Serum esterase is peculiar in that it has a very broad area of activity and maximum activity is at a comparatively low pH. The skin used in these tests was abdominal skin obtained at postmortem examina- tions. It should be pointed out that lipase assays, especially over the pH range, are unsatisfactory generally and all these figures are probably more indicative than quantitative. DISCUSSION It is apparent that the lipases of the dermatophytes, serum and skin can hydrolyze g]ycero] triacetate and that the hydrolyric enzymes are sensitive to a low pH. This property plus some of the properties mentioned earlier make g]ycero] triacetate a suitable source of a prolonged and controlled level of acetic acid whenever it is desired in chemotherapy or for the main- tenance of acidic conditions on the surface of the skin. Another fortunate characteristic is the lack of toxicity or sensitivity to both the glyceride and acetic acid. Apparently lipase may or may not be present upon the surface of normal skin, depending upon factors unknown to us. Recently Nicolaides and Wells (4) cited the sebaceous gland duct and hair-shaft canal as the location