[Effect of antioxidants and complexons on the stability of the microbiological standard for mycoheptin]. / Izuchenie vliianiia antioksidantov i kompleksonov na stabil'nost' mikrobiologicheskogo standarta mikogeptina.

Stability is one of the most important indices of the quality of antibiotic microbiological standards. At present the expiry date of the mycoheptin standard (a specially purified preparation) is 1 year when stored in sealed ampoules in an inert gas at a temperature of -20 degrees C. To prolong the expiry date of the standard the effect of various antiohidants and complexons on its stability was studied with the method of "accelerated aging". Sodium hexametaphosphate and Trilon B were tested as complexing agents and propyl gallate, ionol, N-phenyl-2-napththyl amine, mannitol and their mixtures were tested as antioxidants. The substances were applied in an amount of 3 per cent of the antibiotic weight. The favourable effect of the complexons on mycoheptin stability was shown. Their stabilizing effect was potentiated by addition of certain antioxidants.

[Physicochemical and biological characteristics of mycoheptin components A1 and A2]. / Fiziko-khimicheskaia i biologicheskaia kharakteristika komponentov A1 i A2 mikogeptina.

Mycoheptin, an original antifungal polyenic antibiotic is a complex of several heptaen components. 2 heptaen components designated as mycoheptins A1 and A2 were isolated from the mycoheptin complex with the counter-current distribution technique in a system of methanol-chloroform-forate buffer, pH 8.3 (2:2:1). It was found that component A2 was the main one. Its content in the preparation is at least 80 per cent. The components were studied comparatively with respect to the elemental composition, UV and IR spectra, distribution coefficients in different solvent systems, specific rotation, biological activity and acute toxicity. Both components are original in the subgroup of "nonaromatic" heptaens. Mycoheptin A1 has a lower biological activity and toxicity but its chemotherapeutic efficiency is higher.

[Study of the possibility of stabilizing a levorin microbiological standard]. / Izuchenie vozmozhnosti stabilizatsii mikrobiologicheskogo standarta levorina.

The effect of a number of factors, providing increased stability of the levorin microbiological standard was studied. It was shown that air-tight packing and inert gas atmosphere (antibiotic storage in ampoules sealed under nitrogen) significantly increased the antibiotic stability. It was also shown that hydrochinone had the highest positive effect on levorin stability.

[Effect of gamma-irradiation on some biological and physico-chemical properties of polyene antibiotics]. / Vliianie gamma-oblucheniia na nekotorye biologicheskie i fiziko-khimicheskie svoistva polienovykh antibiotikov

Deep effect of gamma-rays on polyenic antibiotics was studied. It was shown that gamma-radiation induced radiation-chemical oxidation of the substances. The chromatographic analysis showed that the levorin degradation products were identical to the polyenic products of the antibiotic oxidative destruction. As for mycoheptin and amphotericin B, destruction of their molecules to non-polyenic products was observed. It was found that toxicity of the levorin aromatic heptaen did not practically change after gamma-irradiation in high doses. The toxicity of mycoheptin and amphotericin B, non-aromatic heptaens increased after exposure to high doses of gamma-rays.

[Variability of the levorin producer, Actinomyces levoris Krass]. / Izmenchivost' produtsenta levorina--Actinomyces levoris Krass

Natural variation of the levorin-producing organism Act. levoris, strain 28 was studied with respect to the colony morphology and production of levorin and levoristatin. The population of strain 28 consisted of 3 morphological colony types, the main type amounting to 99.7 percent. The strain variation with respect to production of levorin and levoristatin ranged from 20 to 180 and from 0 to 300 percent respectively as compared to the control. Mutant M-28 differing from the initial strain by the colony morphology, moderate phage titer and preferable production of levoristatin was isolated as a result of repeated passages of strain 28 onto agarized Chapek media with starch without maintaining selection. Variants differing from the population of strains 28 and M-28 by the ratio of levorin and levoristatin in the culture fluid were selected. No correlation in production of the above antibiotics by strain 28 was noted. Preparations obtained with strain M-28 differed from those obtained with strain 28 in a significant content of levoristatin.