Kobutimycins A and B, new alkaloid antibiotics produced by a Streptomyces strain.

Newalkaloid antibiotics named kobutimycins A (1) and B (2) (Fig. 1) were isolated from the culture broth of a streptomycete strain No. TA3341, which was isolated from a soil sample collected at Kobutizawa, Yamanashi Prefecture, Japan. The strain has been classified as Streptomyces sp. TA3341. In this communication we wish to report the fermentation, isolation, structural elucidation and biological properties of kobutimycins. A loopful of slant culture of strain TA3341 was inoculated into a 500-ml Erlenmeyer flask containing 1 10 ml of production medium consisting of glycerol 2%, Bacto-Soytone 1%, CaCO3 0.4% (pH 7.0 before autoclaving), and cultured at 27°C on a rotary shaker (180rpm) until the production reached maximum in 2 days. The broth filtrate (5 liters) was extracted twice with ethyl acetate (5 liters x 2 times). The extract was concentrated to dryness under reduced pressure, and the crude residue (1.25 g) was applied to a slica gel column (100ml) equilibrated with CHC13. The column was developed with 300 ml ofCHCI3 MeOH(100 : 1). The active fractions were pooled and concentrated to give 57mg of oily residue. From the residue, two components 1 and 2 were purified by preparative HPLC (Capcell Pak C18 SG120, 20x250mm, Shiseido) using MeOHH2O (7 : 3) as solvent system with detection at 254nm. These active eluates were concentrated