240 



DESCRIPTIONS OF ANTIBIOTICS 



bivalent metallic ion complex. Precipitate slurried 

 in water and a methanolic solution of the precipi- 

 tate adjusted to pH 2.5 to precipitate impvirities. 

 Solution adjusted to pH 7.0 to precipitate the 

 antibiotic (131). II. Adsorbed from broth-filtrate 

 on Florisil or charcoal columns. Developed with 

 acidic alcohol or acetone at pH <5.0 under ultra- 

 violet light. First band (blue) discarded; yellow 

 band which follows is active. Eluate concentrated 

 in vacuo. Concentrate taken uj) in butanol, re- 

 concentrated, and precipitated from concentrate 

 with absolute ether (15). III. Earth metals pres- 

 ent in, or added to the whole broth at pH 7.0 to 

 8.5 precipitate chlortetracycline as a salt . All 

 solids filtered off, and wet cake extracted with 

 n-l)utanol, isopropanol, or sec -butanol at pH 1.2 

 to 1.4 (adjusted with sulfuric or hydrochloric 

 acids). Extracts containing the sulfate shaken 

 with sodium chloride solution to salt out chlor- 

 tetracycline. (This has the effect of increasing the 

 distribution coefficient of chlortetracycline where 

 K = C solvent /C aqueous.) Solvent concentrated 

 under reduced pressure to incipient precipitation, 

 chilled, and pH adjusted to 0.8 to precipitate the 

 antibiotic. Extracts containing the hydrochloride 

 are concentrated under reduced pressure at 45- 

 55° C, added to/3-ethoxyethanol-ethanol-HCl, and 

 cooled (60-62, 121). Three purification procedures 

 are used: (a) Crude chlortetracycline dissolved in 

 such basic compounds as triethylamine, ammonia, 

 ethanolamine, or morpholine in a lower alcohol 

 (such as ethanol) or a lower alkoxy-lower alkanol 

 (2-ethoxyethanol or ethylene chlorohydrin), filter- 

 ing off insoluble impurities and acidifying (85). 

 (b) Aciueous solution of crude chlortetracycline 

 treated at pH 3.0 with an anionic sulfuric acid 

 derivative such as di-(2-ethylhexyl) sidfosuccinate 

 ("Aerosol OT"). The salts thus formed are ex- 

 tracted into methyl isobutyl ketone, ethylene 

 dichloride, or n-propyl acetate, decolorized, then 

 concentrated under reduced pressure at <55°C 

 and acidified (86). (c) Heavy metal chelating 

 agents are used to sequester impurities before 

 I)recipitating the antibiotic as a salt. Such agents 

 include various aminopolycarboxylic acids, svich 

 as (ethvlenedinitrilo)tetraacetic acid and others 

 (132). ■ 



Chemical and phi/sical prupertiea: Ami)hoteric 

 (88). Free base: Yellow, acicidar to bladed crystals 

 (15, 88); m.p. 168-109°C (decomposition) (12). 

 Soluble in water to 0.5 to 0.6 mg per ml at 25°C. 

 Very soluble in aqueous solutions above pH 8.5, 

 dioxane, pyridine, Cellosolves, and carbitol (12, 

 15). Soluble in methanol, ethanol, butanol, ace- 

 tone, ethyl acetate, and benzene. Insoluble in 

 ether and petroleum ether. Ultraviolet absorption 



spectrum maxima at 230, 262.5, and 367.5 vajj. (0.1 

 N HCl) ; at 255, 285, and 345 m^ (0.1 N NaOH) 

 (12) and at 230, 275, and 367.5 m,x (water) (35). 

 Infrared spectrum given in reference 15. [a]'^ = 

 — 275.0° (methanol) (12). Treatment with alco- 

 holic FeCls gives a green-brown color with re- 

 flected light and a reddish color with transmitted 

 light (12). Fluoresces intensely yellow in neutral 

 or slightly alkaline solution, changing to blue in 

 marked alkaline solution or after heating. No 

 fluorescence in acid solution (22). Alkaline fusion 

 products include 5-chlorosalicylic acid, dimethyl- 

 amine, and ammonia. Other degradation products 

 given in reference 40. Reductive dehalogenation 

 with 10 per cent palladium on charcoal and 1 mole 

 of triethylamine yields tetracycline (68). Acid 

 degradation products include biologically active 

 anhydrochlortetracycline (water is removed from 

 ring C) (104). Heating produces biologically in- 

 active, nontoxic isochlortetracycline (127, 128). 

 Chlortetracycline is 7-chloro-4-dimethylamino- 

 l,4,4a,5,5a,6,ll,12a-octahydro-3,6, -10,12,12a, 

 pentahydroxy -6 - methyl -1,11- dioxo - 2 - naphtha - 

 cenecarboxamide. C22H23N2O8CI: C = 55.10%; 

 H = 4.90%; N = 5.72%,; CI = 7.27%. Structural 

 formula (39, 88) given in Chapter 6. Forms com- 

 ple.xes with metal halides (41), and salts with 

 metals and acids. Hydrochloride: Clear vitreous 

 lemon-yellow tabular or orthorhombic crystals 

 (12, 15). Decomposes without melting at >210°C 

 (12, 20), or darkens at 208°C; m.p. 234-236°C (de- 

 composition) (88, 121). Soluble in water to 14 mg 

 per ml at 25°C (12). Soluble in methanol. Slightly 

 soluble in ethanol. Soluble in acetone to 0.13 mg 

 per ml at 25°C. Ultraviolet absorption spectrum 

 maxima at 229, 251, 265, and 370 m^i (pH 4.3, 0.1 

 M KH.2PO4 buffer); at 223, 240, 248, and 276 m^ 

 (pH 8.9, 0.1 M K2HPO4 buffer) (15) and at 224 nip 

 (e = 29,480) 254 m/x (« = 14,635), 287 m^ (« = 

 14,378) and 346 m^ (e = 7,008) (in 0.25 N NaOH) 

 (106). [a]f = -235° (c = 1 per cent in water) (88). 

 Crystallographic data given in references 12, 15, 

 and 16. pKa' = 3.4, 7.4, and 9.2 (39). Most stable 

 at about pH 2.0. Stable at pH 1 to 10 at low tem- 

 peratures for 18 hours, but loses 50 per cent of 

 activity at 37°C overnight (3). In distilled water, 

 65 per cent of initial activity remains after heat- 

 ing at 100°C for 15 minutes. In pH 7.0 phosphate 

 buffer, 0.062 M, under the same conditions, only 

 0.44 per cent of the activity remains (107). Meth- 

 anolate: Yellow plates; m.p. 172-174°C (decom- 

 position). Very stable to drying (88). Ca salt: 

 Amorphous. Decomposes over a range of 200- 

 300°C with gradual darkening at lower tempera- 

 ture (121). 



Biological activity: Bacteriostatic. Active on 



