Fibrostatin E

Fibrostatins, potent inhibitors of prolyl hydroxylase, were isolated as orange crystals from the culture broth of strain No. 23924, which was identified as Streptomyces catenulae subsp. griseospora. In vitro inhibitory activity (ID50 value) of fibrostatins A, B, C, D, E and F against prolyl hydroxylase of chick embryos was 23, 39, 29, 180, 10 and 14 microM, respectively.

The structures of six inhibitors of prolyl hydroxylase, fibrostatins A, B, C, D, E and F produced by a strain of Streptomyces, were deduced to be 1, 2, 3, 4, 5 and 6, respectively, from chemical and spectroscopic evidence, especially from extensive 13C NMR studies including selective decoupling and low power selective decoupling experiments monitored by 13C-1H long-range couplings. These compounds are the first naturally occurring 2,6,7- or 3,6,7-tri-substituted or 2,3,6,7-tetra-substituted 5-hydroxy-1,4-naphthoquinone inhibitors possessing N-acetyl-L-cystein-S-yl moieties in the molecule.