A new platelet aggregation inhibitor, bassiatin, was isolated from the cultured broth of Beauveria bassiana which had been isolated from a soil sample collected in Yunnanprovince, China. The structure of bassiatin was determined to be (35,6i^)-4-methyl-6-(l-methylethyl)-3-phenylmethyl-l ,4perhydrooxazine-2,5-dione by NMRanalysis, X-ray crystallographic analysis and chemical synthesis. Bassiatin inhibited ADP-induced aggregation of rabbit platelets with the IC50 being 1.9 x 10~4m.

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Phosphatoquinones A and B were isolated from the cultured broth of Streptomyces sp. TA-0363 and their structures were elucidated by spectroscopic analyses. Phosphatoquinones A and B inhibited the protein tyrosine phosphatase activity prepared from human Ball-1 cells with IC50 of 28 /xm and 2.9^m, respectively. Therefore, we have screened PTPase inhibitors from microbial metabolites by an assay in vitro using a CD45-enriched membrane fraction of Ball-1 cells6). As a result, we found that a strain TA-0363 produced new PTPase inhibitors named phosphatoquinones A (1) and B (2). Herein, the isolation, structure elucidation and biological activities of (1) and (2) are described. TaxonomyThe vegetative mycelium was well developed. The aerial mycelium was moderately short with simple branches and formed flexuous spore chains with 102 0 spores per chain. The spores were oval in shape (0.7~0.9 x0.9~1.1jim) with a warty surface. No sporangia, motile spores or fragmentation of mycelium were observed. The whole-cell hydrolysate contained LL-diaminopimelic acid. The predominant menaquinones were MK-9(H6) and MK-9(H8).pp. 75 -80 The cultural and physiological characteristics of strain TA-0363 are shown in Table 1 and 2, respectively. Based on these characteristics described above, strain TA-0363 belongs to the genus Streptomyces. Strain TA-0363 has been deposited in the National