Semicochliodinol A and B: inhibitors of HIV-1 protease and EGF-R protein tyrosine kinase related to asterriquinones produced by the fungus Chrysosporium merdarium.

The known bisalkylated 2,5-dihydroxybenzoquinones didemethylasterriquinone D and isocochliodinol as well as the new metabolites semicochliodinol A and B have been isolated as inhibitors of HIV-1 protease from the culture broth of the fungus Chrysosporium merdarium P-5656. The structures were elucidated by spectroscopic methods. The NMR spectra of two compounds were completely assigned. The metabolites inhibit HIV-1 protease with an IC50 value as low as 0.17 microM and epidermal growth factor receptor protein tyrosine kinase at 15 to 60 microM and are therefore valuable lead compounds for these targets. Molecular modelling of the HIV-1-protease-inhibitor complexes showed hydrogen bonding between the dihydroxybenzoquinone moiety of didemethylasterriquinone D and isocochliodinol to both active-site aspartic acids (Asp25/Asp25') of the protease and the indole parts of the inhibitors filling the P2 and P2' pockets of the protease.

Further minor metabolites of staurosporine produced by a Streptomyces longisporoflavus strain.

From the staurosporine producing strain R-19 Streptomyces longisporoflavus various minor metabolites were isolated: They include new compounds with a keto function at carbon 4' of staurosporine and several metabolites related to TAN-1030A. The new structures were elucidated by spectroscopic methods, mainly 1H NMR and 13C NMR and by comparison with TAN-1030A. The new compounds inhibited protein kinase C with IC50 values in the micromolar range with the exception of those compounds that are alkylated at the lactam nitrogen.

Paeciloquinones A, B, C, D, E and F: new potent inhibitors of protein tyrosine kinase produced by Paecilomyces carneus. II. Characterization and structure determination.

Paeciloquinones A to F and versiconol have been isolated as inhibitors of protein tyrosine kinases from the culture broth of the fungus Paecilomyces carneus P-177. The structures of the new anthraquinones were determined by spectroscopic methods, mainly 1H NMR and 13C NMR. The substitution pattern was established by investigation of the respective methylated derivatives.

Paeciloquinones A, B, C, D, E and F: new potent inhibitors of protein tyrosine kinases produced by Paecilomyces carneus. I. Taxonomy, fermentation, isolation and biological activity.

Paeciloquinones A to F as well as versiconol have been isolated as inhibitors of protein tyrosine kinase from the culture broth of the fungus Paecilomyces carneus P-177. The novel anthraquinones inhibit epidermal growth factor receptor protein tyrosine kinase in the micromolar range. Two compounds, paeciloquinones A and C, are potent and selective inhibitors of the v-abl protein tyrosine kinase with an IC50 of 0.4 microM. Dependent on the fermentation conditions, partially different sets of paeciloquinones may be produced. An HPLC method allows separation of all major active components.

A nitro analogue of staurosporine and other minor metabolites produced by a Streptomyces longisporoflavus strain.

From the staurosporine-producing strain Streptomyces longisporoflavus R-19 various minor metabolites were isolated: They include a new compound with a nitro function in C-4' and other metabolites related to staurosporine. The new structures were elucidated by spectroscopic methods, mainly 1H NMR and 13C NMR and by comparison with TAN-1030A. The new compounds inhibited protein kinase C with IC50 values in the nanomolar range.

Solution structures of the lantibiotics duramycin B and C.

The solution structures of the lantibiotics duramycin B in H2O/2H2O (9:1) and duramycin C in (2H3)acetonitrile/H2O (1:1) have been determined by NMR followed by distance-geometry and restrained-molecular-mechanics calculations. The constitution and location of three thioether bridges and a lysinoalanine ring system could be established by unambiguously assigned NOE contacts between the bridging side chains. Model building based on NMR constraints resulted in a U-shaped topology of the tetracyclic 19-peptides with a turn around Pro9 and a kink along a virtual line from residues 5 to 13. This clamp-like conformation is stabilized by the thioether bridges and is additionally supported by an antiparallel beta-strand-like structure of the N-termini and C-termini and the inherent amphiphilicity of duramycin-type lantibiotics. The duramycins B and C differ mainly in the relative mobilities of their rings A, C and D. Duramycin B is closely related to cinnamycin with an exchange of Phe10 to leucine, whereas duramycin C differs from duramycin B by three conserved and two non-conserved amino-acid exchanges.

Mode of action of the lanthionine-containing peptide antibiotics duramycin, duramycin B and C, and cinnamycin as indirect inhibitors of phospholipase A2.

Effects of the lanthionine-containing peptide antibiotics duramycin, duramycin B, duramycin C and cinnamycin on the activity of phospholipase A2 from six different sources were studied, and their mode of action was investigated. The four antibiotics inhibited potently all tested phospholipases A2, with IC50 values of around 1 microM, using phosphatidylethanolamine or [1-14C]oleate-labelled Escherichia coli, whose phospholipids are rich in phosphatidylethanolamine, as substrates. No inhibition was observed when the substrate was phosphatidylcholine. Binding of the antibiotics to the lipid fraction of E. coli could be demonstrated by co-sedimentation with whole, but not with lipid-depleted E. coli. In addition, preincubation of duramycin B with vesicles of phosphatidylethanolamine, but not those of phosphatidylcholine, prevented the inhibition of phospholipase A2 activity. The interaction of duramycin B and C, but not that of the biologically inactive compounds actagardine and the duramycin B trisulphoxide, with phosphatidylethanolamine was demonstrated using circular dichroism studies. On the other hand, no interaction of duramycin B with phosphatidylcholine could be demonstrated. A strict correlation between the physico-chemical interaction of the studied lantibiotics, demonstrated by circular dichroism spectroscopy, and their inhibition of phospholipase A2 was observed. These results suggest that lanthionine-containing peptide antibiotics inhibit phospholipase A2 indirectly by specifically sequestering the substrate phosphatidylethanolamine. This mode of action is analogous to the one described for the protein lipocortin.

Duramycins B and C, two new lanthionine containing antibiotics as inhibitors of phospholipase A2. Structural revision of duramycin and cinnamycin.

Duramycins B and C, two new lanthionine containing antibiotics, have been isolated from Streptoverticillium strain R2075 and Streptomyces griseoluteus (R2107). The known antibiotics duramycin and cinnamycin were reisolated from Streptoverticillium hachijoense (DSM 40114) and Streptomyces longisporoflavus (DSM 40165). The structures of these latter two compounds should be revised by changing amino acid residue 3 to glutamine and 17 to asparagine, respectively. Cinnamycin therefore seems to be identical to Ro 09-0198. Leucopeptin has been shown to be identical to duramycin. Physico-chemical data of these compounds provide evidence for a similar structure for all duramycin antibiotics. All compounds of this group inhibit human phospholipase A2 at a concentration of 10(-6) molar.

Strobilurins F, G and H, three new antifungal metabolites from Bolinea lutea. I. Fermentation, isolation and biological activity.

Three new strobilurins F, G and H, antibiotics with antifungal activity, were isolated from cultures of Bolinea lutea Sacc. These new compounds differ from previously described analogs in their aromatic substitution. An HPLC method allows complete separation of all the components.

The photodeactivation of hedamycin, an antitumor antibiotic of the pluramycin type.

The cytotoxicities of hedamycin and photohedamycin A as well as of kidamycin and isokidamycin were determined using HeLa cell cultures. Photohedamycin A proved to be 15 times less cytotoxic than hedamycin thus explaining the loss of biological activity observed for solutions of hedamycin left in daylight. The fact that photohedamycin A is less active than hedamycin, and isokidamycin less than kidamycin points to the important role the rings E and F play in the biological activity of hedamycin and kidamycin.