Preparation and Properties of Circulin

The culture medium, after the growth of B. circulans, is filtered, and the antibiotic is adsorbed on active charcoal (Daroo G-60) and eluted into tertiary butanol saturated with acidified water. The circulin, isolated as its sulfate, is further purified by successive chromatographic separations on active charcoal. 

The biological assay of circulin was carried out by the technique of Murray et al. (431). The elementary analysis of the free base gives the following formula (Cs9H7409Ni2)n which corresponds to a cyclic peptide. 

The circulin sulfate is an amorphous white powder, melting at 226-228 C. is levorotatory [a]o = —61 6 (c = 1.25% in water) and is very soluble in water, but less so in the lower alcohols, and is insoluble in the nonpolar solvents. The circulin sulfate can be chromatographed on paper, and with the solvent (50 parts n-butanol + 25 parts acetic acid + 25 parts water) appears to be homogeneous. This basic peptide can also be obtained as the picrate, helianthate, Reineckate, and hydrochloride. The formol, 2,4-dinitrofluorobenzene, and acetyl derivatives have been described by Peterson and Reinecke (458). 

The circulin obtained from B. circulans Q 19 has been resolved into at least five different constituents by chromatography on celite (354a). 

The industrial production of circulin has been described by Nelson et al. (432). 

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