. The actinomycetes. Actinomycetales. DESCRIPTIONS OF ANTIBIOTICS 267 tatively from sohitions of ethanolic ;iimnonia as the ammonium salt, leaving almost all impurities in solution. This colorless, crystalline salt is un- stable in the dry state and decomposes to the pure antibiotic in vacuo (10). Chemical and physical properties: Macrocyclic peptide lactone, containing eight amino acids. Weakly basic (1) or amphoteric (3). Base: Color- less amorphous powder (10). Soluble in lower alco- hols and ketone, benzene, chloroform, carbon tetrachloride, carbon disulfide, ethyl acetate, ether, 1 .V HCl
. The actinomycetes. Actinomycetales. DESCRIPTIONS OF ANTIBIOTICS 267 tatively from sohitions of ethanolic ;iimnonia as the ammonium salt, leaving almost all impurities in solution. This colorless, crystalline salt is un- stable in the dry state and decomposes to the pure antibiotic in vacuo (10). Chemical and physical properties: Macrocyclic peptide lactone, containing eight amino acids. Weakly basic (1) or amphoteric (3). Base: Color- less amorphous powder (10). Soluble in lower alco- hols and ketone, benzene, chloroform, carbon tetrachloride, carbon disulfide, ethyl acetate, ether, 1 .V HCl, and 1 X NaOH. Slightly soluble in water. Insoluble in petroleum ether (1, 9). \^l° 350 (E\7n. 71) with a shoulder at 303 (^I?,„ 34) (3). [a]f = +° (c = 2 per cent in methanol) (1). Positive tests for an active methylene group, pep- tide bond, ester, and amide groupings (hydroxamic acid test). Brownish red color with F'eCh test. Weakly positive Folin-Ciocalteau and Bayer tests. Negative ninhydrin and Sakaguchi tests (1, 3). pKa' = (10 per cent acjueous ethanol). Stable at acid pH and neutrality; inactivated by alkali. Esterihcation destroys microbiological activity. Calculated formula: C44H620„N8-H20: C = ; H = ; N = ; N—Me = Molecular weight, 800 to 900. Proposed structure (9): OH negative bacteria and C. albicans. Active in vivo against experiniental D. pneumomae and Staph, aureus infections in mice and E. histolytica in- fections in rats and dogs. Some antirickettsial activity; no antiviral activity. Active against bovine mastitis, infectious bronchitis of chicks, and panleukemia of cats (1. 4, 6). Active in ovo on pleuropneumonia-like organisms (avian) (7). Intermediate activity on sarcoma 180 in mice (8). Toxicity: LD50 (mice) mg per kg intra- peritoneally, >2000 mg per kg subcutaneously, >3000 mg per kg orally. Etamycin produces a reversible leukopenia in dogs (1). At certain con- centrations, given orally or subcutaneousl
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