New Cdc25B tyrosine phosphatase inhibitors, nocardiones A and B, produced by Nocardia sp. TP-A0248: Taxonomy, fermentation, isolation, structural elucidation and biological properties

Strain TP-A0248 which produces two new Cdc25B tyrosine phosphatase inhibitors and also possessing antifungal activity, designated nocardiones A (1) and B (2), was considered to belong to the genus Nocardia on the basis of literature comparison of chemotaxonomic properties. The nocardiones were isolated by solvent extraction of fermentation broth of Nocardia sp. TP-A0248 and purified by the conventional column chromatography. Spectroscopic studies led to determination that 1 and 2 belong to a class compound of naphtho[1,2-b]furan-4,5-diones. Compound 1 inhibited the activity of Cdc25B, PTP1B and FAP-1 protein tyrosine phosphatases at a concentration of 10 μM. It also showed moderate in vitro antifungal and cytotoxic activity.