ABSTRACT
Two promising antibiotics, JF-A and JF-B were isolated from the chloroform extract of a Banglaeshi Streptomyces strain. The mean zones of inhibition produced by the chloroform extract [400 ug/disc], JF-A [200 ug/disc] and JF-B [200 ug/disc] against 19 pathogenic bacteria were found to be 9-50, 12-38 and 10-41 mm while those produced by a standard antibiotic, kanamycin were 11-40 mm at 30 ug/disc. MICs of JF-A and JF-B were determined to be 64 ug/ml against Bacillus subtilis and 64 and 128 ug/ml against Shigella sonnei, respectively. The extract and the antibiotics were also tested for cytotoxicity against Artemia salina nauplii and LC50 values of 23.26, 18.05 and 32.27 ug/ml were obtained. 90% mortality of shrimp nauplii was observed at 69.18, 50.12 and 110.91 ug/ml, respectively. In a potato disc bioassay, the chloroform extract at 25 ug/disc demonstrated 37.39% inhibition of crown gall tumour induced by G -ve Agrobacterium tumefaciens B6 and the result was statistically significant [P < 0.05]. The sub-acute toxicity studies on the JF-A and JF-B reflected innocuous nature of these antibiotics on hepatic, renal and haemopoietic system of rats at 1 mg/kg b.w. on daily administration for 21 consecutive days. This is also confirmed by detailed histopathological studies. No mortality was observed in experimental animals