Sibanomicin, a new pyrrolo[1,4]benzodiazepine antitumor antibiotic produced by a Micromonospora sp.

A new memberof the anthramycin group of antibiotics1"'115, sibanomicin has been found in the culture filtrate of Micromonospora sp. SF2364. The antibiotic exhibited a marked antitumor activity in mice bearing leukemia P388 cells and a weak activity against Grampositive bacteria. In this communication, the production, isolation, characterization, structural elucidation and biological properties of the antibiotic are reported. A slant culture of strain SF2364 was inoculated into a 100-ml Erlenmeyer flask which contained 20ml of a seed medium consisting of starch 2.0%, glucose 1.0%, wheat germ 0.6%, Polypepton (Daigo Eiyo Kagaku) 0.5 %, yeast extract 0.3%, soybean meal 0.2% and CaCO30.1% (pH 7.0). The inoculated flask was cultured on a rotary shaker (220rpm) at 28°C for 4 days. The first seed culture (4 ml) was inoculated into 80 ml of the same mediumin a 500-ml Erlenmeyer flask (shaking at 28°C for 2 days). The second seed culture (50ml) was added to a 5liter Erlenmeyer flask containing 1 liter of the same medium (shaking at 28°C for 2 days). The third seed culture (1 liter) was transferred into a 50-liter jar fermentor containing 35 liters of the same mediumand fermentation maintained at 28°C for 2 days. The fourth seed culture (6 liters) was added to a 300-liter fermentor containing 200 liters of the production medium (sucrose 3.0%, cotton seed meal 1.0%, wheat germ 1.0%, soluble vegetable protein 0.6%, CaCO3 0.1 %, MgSO4-7H2O 0.1 %, FeSO4-7H2O 0.0005% and CoCl2-6H2O 0.0005% in a tap water, pH 7.0 before sterilization) and fermentation was carried out at 28°C for 3 days with aeration of 100 liters/minute, and agitation of 100rpm (0-41 hours) and 150rpm (41-72 hours). The activity of the antibiotic was assayed by the paper-disc method using Escherichia coli (DNArepair deficient mutant) as the test organism. 1281