TMC-86A, B and TMC-96, new 20S proteasome inhibitors with an epoxy-β-aminoketone moiety, were isolated from the fermentation broth of Streptomyces sp. TC 1084 and Saccharothrix sp. TC 1094, respectively. TMC-86A, B and TMC-96 inhibited the chymotrypsin-like and peptidylglutamyl-peptide hydrolyzing activities of 20S proteasome with the following IC50 values: TMC-86A, 5.1 μM and 3.7 μM; TMC-86B, 1.1 μM and 31 μM; TMC96, 2.9 μM and 3.5μM, respectively. TMC-86A, B and TMC-96 exhibited the weak inhibitory activity against the trypsin-like activity of 20S proteasome with IC50 values of 51 μM, 250μM, and 36μM, respectively. They did not inhibit m-calpain, cathepsin L, and trypsin at 100 μM, suggesting their high specificity for proteasome. Taxonomy of the producing strains is also described.
During the course of our screening for natural products from fungi, extracts of several cultures were found to make a family of related resorcylic acid lactone compounds, which are potent inhibitors of MEK kinase. Comparative and empirical studies of fermentation conditions improved the titers of the compounds of interest. Striking changes in the ratios and amounts of the major and minor compounds in some cases were achieved by manipulations of media composition.
A resorcylic acid lactone, L-783, 277, isolated from a Phoma sp. (ATCC 74403) which came from the fruitbody of Helvella acetabulum, is a potent and specific inhibitor of MEK (Map kinase kinase). L-783, 277 inhibits MEK with an IC50 value of 4nM. It weakly inhibits Lck and is inactive against Raf, PKA and PKC. L-783, 277 is an irreversible inhibitor of MEK and is competitive with respect to ATP. L-783, 290, the trans-isomer of L-783, 277, was isolated from the same culture and evaluated together with several semi-synthetic resorcylic acid lactone analogs. A preliminary structure-activity relationship is presented. Several independent cellbased assays have been carried out to study the biological activities of these resorcylic acid lactone compounds and a brief result summary from these studies is presented.
Funalenone, a phenalene compound that inhibits type I collagenase (MMP-1), was isolated from mycelium of Aspergillus niger FO-5904 by solvent extaction, ODS column chromatography, Sephadex LH-20 column chromatography and reversed phase HPLC. Funalenone inhibited 50% of type I collagenase activity at a concentration of 170 μM, but inhibited 18.3% and 38.7% against 72kDa and 92kDa type IV collagenase, respectively, at a concentration of 400 μM.
Streptomyces sp. WK-5344, a soil isolate, was found to produce structurally related inhibitors of cholesteryl ester transfer protein (CETP). New active compounds, designated ferroverdins B and C, were isolated along with known ferroverdin A from the fermentation broth by solvent extraction, ODS column chromatography and silica gel column chromatography. All ferroverdins showed a dose-dependent inhibitory activity against human CETP. The IC50 values were 21, 0.62 and 2.2 μM for ferroverdins A, B and C, respectively, indicating that ferroverdin B is one of the most potent CETP inhibitors of microbial origin.
The structures of ferroverdins B and C, novel inhibitors of cholesteryl ester transfer protein, were elucidated by spectroscopic studies including various NMR measurements. They are the complex between one Fe2+ and three ligands, that is, two common p-vinylphenyl-3-nitroso-4-hydroxybenzoates and one hydroxy p-vinylphenyl-3-nitroso-4-hydroxybenzoate for ferroverdin B and one carboxylic acid p-vinylphenyl-3-nitroso-4-hydroxybenzoate for ferroverdin C.
Four new antibiotics, TMC-171A (2), B (3), C (4) and TMC-154 (5) have been isolated from the fermentation of fungal strains Gliocladium sp. TC 1304 and TC 1282, respectively. Spectroscopic and degradation studies have shown that TMC-171s and TMC-154 were new members of the TMC-151 class of antibiotics, unique polyketides modified with a D-mannose and a D-mannitol or a D-arabitol. These compounds showed moderate cytotoxicity to various tumor cell lines.
Based on the chemical screening technique, biomolecular-chemical screening has been developed which makes use of two-dimensional TLC analysis of microbial extracts and combines thin-layer chromatography (RP-18) with binding studies towards DNA. In the first dimension the metabolites of the crude microbial extract are separated, and in the second dimension binding properties towards DNA are analysed. An initial screening program with 500 microbial extracts prepared by solid-phase extraction with XAD-16 resin resulted in 17 samples which contained metabolites with significant DNA-binding behavior. Fermentation, isolation and structural characterization led to already known metabolites [phenazine-1, 6-dicarboxylate (1), phencomycin (2), 11-carboxy-menoxymycin B (3), soyasaponine I (4), and (8S)-3-(2-hydroxypropyl)-cyclohexanone (5)], as well as to new secondary metabolites. Fermentation of the producing organisms of the new DNA-binding metabolites, ent-8, 8adihydro-ramulosin (6), (2R, 4R)-4-hydroxy-2-(1, 3-pentadienyl)-piperidine (7), (5R)-dihydro-5-pentyl-4'-methyl-4'-hydroxy-2(3H)-furanone (8), and seco-4, 23-hydroxyoleane-12-en-22-one3-carboxylic acid (9), as well as isolation, structural characterization, and physico-chemical properties are reported.