Abstract:
Zhengguangmycin, an antitumor antibiotic complex consisting of more than ten components, is produced by
Streptornyces pingyangensis n. sp. isolated from a soil sample collected in Pingyang, Zhejiang province. Two components of zhengguangmycin, namely A
2 and A
5 were found to be identical with bleomycins A
2 and A
5 respectively. As bleomycin presently available for clinical use contains bleomycin A
2 as its major component, the biological activities of zhengguangmycin A
5 were studied in comparison with those of zhengguangmycin A
2. The main differences found are as follows; (1) On an equal LD
50 basis the inhibitory effect of A
5 on transplantable esophageal carcinoma SGA-73 in mice is much stronger than that of A
2; (2) The concenrration of A
5 attained in the mouse esophageal carcinoma tissue as determined by microbiological assay is much higher than that of A
2; (3) As shown by light and electron microscopy A
5 appears to be less injurious to the mouse lung than A
2 on an equal body weight dosage basis and (4) A
5 appears to be less toxic to the mouse in acute toxicity experiments. These results suggest that zhengguangmycin A
5 possesses more desirable properties than A
2 as an antitumor agent.
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