Kazutoshi Sakamoto

Improvement of FR901379 production by mutant selection and medium optimization

FR901379 (WF11899A) is a novel echinocandin type of lipopeptide antibiotic produced by Coleophoma empetri F-11899. Micafungin (FK463) is derived from the chemical modification of deacylated FR901379. In the present paper, we performed seven generations strain-breeding, beginning with a wild type, was performed. Selection medium for screening and production medium for high FR901379 production were designed. Sodium chloride content in the selection plate was affected to FR901379 production and shrinkage of the colony size was observed in high producing strains. As selection markers, large colony-shrinking rate and large inhibition circle in the agar-piece method using C. albicans was selected. Using CMA medium with high sodium chloride, 3 mutants, M-1 to M-3, have achieved a high FR901379 production and M-3 showed 5.0 U/mL, while 1.0 U/mL of production was achieved in wild type strain. A-2 medium supplemented with 6% of soluble starch as a carbon source and 0.6% of ammonium sulfate as nitrogen source was also further effective for mutant screening. The FR901379 production of mutant M-4 (fourth generation) increased until 16.0 U/mL. The concentration of the phosphate salt in the medium seemed to inhibit the growth so as to extend the culture period. When the A-3 medium supplemented with low concentration of phosphate salt and magnesium sulfate as a sulfate source was designed and used, mutants with improved production were successively obtained. Finally, variant strain M-7 showed 30.0 U/mL of production, which was about 30 times higher than that of the wild strain.

AS1387392, a novel immunosuppressive cyclic tetrapeptide compound with inhibitory activity against mammalian histone deacetylase

The novel immunosuppressant AS1387392 has been isolated from Acremonium sp. No. 27082. This compound showed a strong inhibitory effect against mammalian histone deacetylase and T-cell proliferation. Further, AS1387392 showed a good oral absorption, and its plasma concentration was higher than that of FR235222, an analog of AS1387392 that inhibited histone deacetylase previously reported. Given these findings, AS1387392 may represent an important new lead in developing immunosuppressant.

Screening and evaluation of new inhibitors of hepatic glucose production

In the course of our screening program for inhibitors of hepatic glucose production in rat hepatoma H4IIE-C3 cells, which were used as model liver cells, five naphtoquinone derivatives—javanicin, solaniol, 9-O-methylfusarubin, 5,10-dihydroxy-1,7-dimethoxy-3-methyl-1H-naphtho[2,3-c]pyran-6,9-dione, 9-O-methylbostrycoidin—and vanillin were selected from our natural product library. These naphtoquinone derivatives inhibited hepatic glucose production at IC50 values of 3.8–29u2009μM, but showed cytotoxicity against hepatic cells after incubation for 48u2009h. However, vanillin showed an IC50 value of 32u2009μM without exhibiting cytotoxicity at 50u2009μM. Therefore, we examined 12 vanillin derivatives to investigate their inhibitory activities against glucose production. Among these analogs, 4-hydro-3-methoxyacetophenone and 5-nitrosalicylaldehyde exhibited stronger inhibition than the other compounds at IC50 values of 25 and 24u2009μM, respectively, with no cytotoxicity at a concentration of 50u2009μM. Hence, 4-hydro-3-methoxyacetophenone and 5-nitrosalicylaldehyde may be useful as a lead compound of anti-type 2 diabetic drugs.