United States Patent Office Patented Apr
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3,509,255 United States Patent Office Patented Apr. 28, 1970 1. 2 biotics Annual, 1953-1954, pages 191-194, Medical En 3,509,255 cyclopedia, Inc., New York, N.Y. PROCESS FOR THE RECRYSTALLIZATION The recovery of nystatin by isopropanol extraction of OF NYSTATIN Harold Mendelsohn, Nanuet, N.Y., assignor to American the whole broth resulting from the fermentation of the Cyanamid Company, Stamford, Conn., a corporation of nystatin producing Streptomyces noursei is described in Maine U.S. Patent No. 2,786,781 to Vandeputte et al. The par No Drawing. Filed July 2, 1968, Ser. No. 741,912 tially purified product obtained by the Vandeputte et al. Int. Cl. A61k 21/00 process is a therapeutically useful product of about 65 U.S. C. 424-123 10 Claims 70% purity. At best, however it is only partially crystal line and for the most part is substantially non-crystalline or amorphous in character. The purification of nystatin ABSTRACT OF THE DISCLOSURE employing methanolic-calcium chloride is also described This disclosure describes a process for preparing highly in U.S. Patent No. 2,832,719 to Vandeputte and in U.S. purified crystalline nystatin by extracting crude nystatin Patent No. 2,865,807 to Dutcher et al. The product ob with acetone which is saturated with sodium iodide, 15 tained by the Vandeputte and Dutcher et al. processes is Sodium thiocyanate, potassium thiocyanate or ammonium a therapeutically useful highly refined product substan thiocyanate; and precipitating highly purified crystalline tially crystalline in character. nystatin from the extract by displacement of the acetone The processes described above produce crystalline ny with water. statin but are objectionable due to the presence of im 20 purities or low yields. They are also objectionable as they are relatively difficult to control and are not of the type BRIEF SUMMARY OF THE INVENTION desired in large-scale commercial operations. The present invention relates to the antifungal anti It is known that pure crystalline nystatin is indicated biotic nystatin (originally termed fungicidin) and more for certain uses in the antifungal field and attempts have particularly, is concerned with an improved process of 25 been made to develop improved, simplified processes of preparing highly purified crystalline nystatin. The present obtaining the pure crystalline material in high yield. At invention is based upon the discovery that crude or par tempts in particular have been made to prepare pure tially purified nystatin may be readily converted to highly crystalline nystatin directly from the relatively crude par purified crystalline nystatin by a process involving (1) tially purified plant material obtained by isopropanol ex slurrying crude nystatin in a solution of acetone which is 30 traction of the whole broth by the use of this material in Saturated with sodium iodide, sodium thiocyanate, potas the methanolic-calcium chloride process. In the past, with sium thiocyanate or ammonium thiocyanate, or mixtures the processes available, this approach has not been found thereof, at a temperature of from about 10° C. to about to be entirely satisfactory or completely successful as the 45 C.; (2) removing undissolved material from the re product obtained was seldom uniform and was also fre Sulting slurry; (3) removing part of the acetone solvent 35 quently contaminated by amorphous material. With con from the resulting solution by evaporation; (4) adding tinued investigation, I have discovered that crude par water to the resulting concentrated solution in an amount tially purified nystatin may be readily converted to highly of at least about one tenth of the volume of salt saturated purified crystalline nystatin by a process comprising two acetone solution; and (5) recovering the resulting precipi basic steps; (A) extracting crude nystatin with acetone tate of highly purified crystalline nystatin. 40 which is saturated with sodium iodide, sodium thiocyanate, potassium thiocyanate or ammonium thiocyanate or any DETAILED DESCRIPTION OF THE INVENTION mixture thereof, and (B) precipitating highly purified crystalline nystatin from the extract by dilution or dis The antibiotic nystatin (fungicidin) and its method of placement of the acetone with water. preparation from Streptomyces noursei are described in 45 Various crude or semi-purified nystatin containing U.S. Patent No. 2,797,183 to Hazen et al. See also Hazen preparations may be employed as starting materials in the et al., "Fungicidin, an Antibiotic Produced by a Soil novel process of the present invention. The mycelial mat Actinomycete,” Proc. Soc. Exptl. Biol. Med. 76, 93 (1950) or crude concentrates prepared therefrom by any of vari and Brown et al., “Effect of Fungicidin (nystatin) in ous extraction and fractional precipitation procedures may Mice Injected with Lethal Mixtures of Aureomycin and 50 be used. Partially purified nystatin prepared by any of the Candida albicans,” Science 117, 609 (1953). The anti various procedures known to the art, such as the isoprop biotic is referred to hereinafter by the single term “ny anol extraction of the whole broth, may also be used. In statin.' short, any nystatin containing material may be employed Crude concentrates of nystatin can be prepared by ex as a starting material in the purification process of the tracting the myceliel mat with several portions of methanol 55 present invention provided only that it be substantially and then processing the methanolic solution by fractional free from water. precipitation with ethyl acetate, washing the precipitate The extraction step is readily carried out by merely with 0.85% sodium chloride solution, redissolving in slurrying the nystatin containing starting material in a methanol and fractional precipitation with diethyl ether. Solution of acetone saturated with sodium iodide, sodium See Hazen et al., U.S. Patent No. 2,797,183, supra. Low 60 thiocyanate, potassium thiocyanate, ammonium thiocya yields of active crystalline material can be obtianed from nate or mixtures thereof. The slurry is stirred for a pe the resulting crude concentrates by distribution between riod of time of from a few minutes to about an hour n-butanol and saline and by partial precipitation from at a temperature of from about 10° C. to about 45° C. methanol. Crystalline nystatin of high purity has been ob Neither the amount of salt saturated acetone solution tained by distribution of partially purified nystatin con 65 employed nor the stirring time is critical since a nystatin and Brown et al., “Effect of Fungicidin (nystatin) in salt complex is rapidly formed with is extremely soluble butanol, methanol, water and hexane and allowing this in acetone. To illustrate, the solubility of nystatin in ace system to stand exposed to air evaporation until a crop tone at room temperature (25-27 C.) is approximately of crystals collects at the interface. Dutcher et al., Anti 49 units/milliliter. In contrast, the solubility of nystatin 3,509,255 3 4. in salt saturated acetone solutions at 25-27 C. is set ceous earth was added and the impurities were removed forth in Table I below: by filtration. The filter cake was washed with 25 milli TABLE I liters of fresh sodium thiocyanate saturated acetone. The Salt saturated acetone Solubility of nystatin combined filtrates were concentrated under vacuum at solution therein, units/ml. 25-35 C. and 40 milliliters of water was added. After NaI/acetone ------------------------ 786,000 concentration to about one-half volume 75 milliliters of NaSCN/acetone -------------------- 278,000 4:1 (v./v.) Water-acetone solution was added and the KSCN/acetone --------------------- 1,000,000 concentration to one-half volume was repeated. The ny NH4SCN/acetone ------------------- 900,000 Statin precipitated during this displacement of acetone 10 with water. To the concentrate was added 35 milliliters However, illustrative amounts of salt saturated acetone of the 4:1 water-acetone solution. The process was com solution which may be conveniently used with various pleted by aging for 1% hours at 40° C. followed by 2 types of nystatin containing starting materials are set hours at room temperature (27 C.). The crystallized forth in the specific examples appended hereinafter. nystatin was filtered, washed with the water-acetone solu The salt saturated acetone solution may be readily pre 5 tion and dried in vacuo. The yield was 10.01 grams of pared by stirring acetone with an excess of one of the crystalline nystatin assaying 4113 units/milligram (mi four salts enumerated hereinabove or with an excess of crobiological assay). a mixture of two or more of these salts at room tem Example 2-Recrystallization of nystatin from crude peratures. After the acetone is salt saturated, it is filtered from the excess insoluble salt. Salt mixtures which nystatin using sodium iodide saturated acetone are particularly useful in the present process are A Saturated solution of sodium iodide in acetone at NaI--NHSCN, NaI-I-NasCN, and NaSCN--KSCN. 25-27 C. was prepared. A 50 gram portion of crude The extraction step is conveniently carried out at a tem nystatin, having a potency of 2650 units/milligram by perature of from about 10° C. to about 45 C., preferably microbiological assay, was added to 200 milliliters of the at room temperature (25-30 C.). After the extraction 25 Sodium iodide Saturated acetone. The nystatin was essen of the nystatin containing starting material is complete, tially dissolved by stirring for 1 hour. The solution was any undissolved material is removed from the salt satu clarified by centrifuging and decanting the supernatant. rated acetone extract by any convenient means such as The orange colored supernatant had a volume of 250 filtration or centrifugation. The nystatin containing ace milliliters. To 40 milliliters of this supernatant (assay tone extract may be further clarified, if desired, by treat 30 ing 658,400 units/milliliter) was quickly added, with stir ment with charcoal, diatomaceous earth, and the like ring, 128 milliliters of n-butanol followed by 32 milli followed by filtration or centrifugation.