Quercinol, an anti-inflammatory chromene from the wood-rotting fungus Daedalea quercina (Oak Mazegill)

The fungus Daedalea quercina (oak mazegill) was examined for its capability of producing antioxidative and anti-inflammatory compounds. Bioactivity guided fractionation of the extract from a mycelial culture led to the isolation of quercinol, which was identified as (-)-(2S)-2-hydroxymethyl-2-methyl-6-hydroxychromene 1 by NMR and X-ray analyses. The cryptic hydroquinone 1 shows a broad anti-inflammatory activity against cyclooxygenase 2 (COX-2), xanthine oxidase (XO), and horseradish peroxidase (HRP) at micromolar concentrations.

N'-methylniphimycin, a novel minor congener of niphimycin from Streptomyces spec. 57-13

A novel natural niphimycin analog, N'-methylniphimycin was isolated from the culture broth of the Streptomyces spec. 57-13. The chemical constitution was elucidated from the physico-chemical properties, NMR techniques and mass spectrometry to be a 36-membered macrolide related to azalomycin F5a, shurimycin B and RS-22C. N'-methylniphimycin displayed moderate activity against some yeasts and filamentous fungi.

A solution NMR study of the selectively 13C, 15N-labeled peptaibol chrysospermin C in methanol

The conformation of the 19-residue peptaibol chrysospermin C in methanol has been investigated by NMR spectroscopy using selective 15N and 13C labeling of the alpha-aminoisobutyric acid (Aib) residues. Complete 1H and 13C sequential assignments, including stereospecific assignments for the heavily overlapped resonances from the two Cbeta methyl groups of the eight Aib residues, are reported for a peptaibol for the first time. An Aib residue followed by a Pro is an exception to previous suggestions regarding stereospecific assignment of the two Cbeta methyl groups of Aib residues. Local nuclear Overhauser effects and 3J(HNC') and 3J(HNCbeta) scalar couplings indicate that the phi angles of the Aib residues are restricted sterically to local conformations consistent with right-handed helices. Despite these constraints on the eight Aib residues, the NMR data for chrysospermin C in methanol are generally most consistent with an ensemble of transient conformations, including backbone conformations inconsistent with helical structures. Initial NMR measurements for chrysospermin C bound to micelles suggest structural and dynamic differences relative to alamethicin bound to micelles which may be related to differences in gating voltages for formation of ion channels.

Effective diameters of ion channels formed by homologs of the antibiotic chrysospermin

Radii of ion channels formed in the lipid bilayer by 4 homologs of the alamethicin-like antibiotic, chrysospermin, were determined using hydrophilic nonelectrolytes. It is shown that the replacement of isovaline amino acid at position 15 of the polypeptide chain by alpha-aminoisobutyric acid results in the decrease in the channel effective radius from 1.2 +/- 0.15 to 0.94 +/- 0.1 nm and a respective 2.5-fold decrease in channel conductance.

Ampullosporin, a new peptaibol-type antibiotic from Sepedonium ampullosporum HKI-0053 with neuroleptic activity in mice

Ampullosporin (I; Ac-Trp-Ala-Aib-Aib-Leu-Aib-Gln-Aib-Aib-Aib-Gln-Leu-Aib-Gln-Leuol) was isolated from the mycelium of Sepedonium ampullosporum as a new 15-membered peptaibol-type antibiotic. The structure was determined by mass spectrometric and two-dimensional NMR experiments. Ampullosporin displays narrow-spectrum antibacterial and antifungal activity, induces pigment formation by Phoma destructiva, causes hypothermia and decreased spontaneous locomotor activity in mice in dosages > 1 mg/kg.

Lipohexin, a new inhibitor of prolyl endopeptidase from Moeszia lindtneri (HKI-0054) and Paecilomyces sp. (HKI-0055; HKI-0096). I. Screening, isolation and structure elucidation

Lipohexin was isolated as a novel lipohexapeptide (I) (C39H68N6O9) from three fungal strains, Moeszia lindtneri HKI-0054, Paecilomyces sp. HKI-0055 and Paecilomyces sp. HKI-0096. The structure was elucidated by detailed mass spectrometric and NMR experiments. The proline-containing peptide displays moderate antibacterial activity against Bacillus subtilis ATCC 6633 and inhibits competitively the prolyl endopeptidase from human placenta.

Chrysospermins, new peptaibol antibiotics from Apiocrea chrysosperma Ap101

Four new members of peptaibol antibiotics, designated as chrysospermins A, B, C, and D, were isolated from the mycelium of Apiocrea chrysosperma Ap101 by solvent extraction, silica gel chromatography and preparative recycling HPLC. Their structures as new nonadecapeptides were settled by detailed spectroscopic analysis and chemical degradation experiments. The chrysospermins display antibacterial and antifungal activity, and induce pigment formation by the fungus Phoma destructiva.

Formation of membrane channels by chrysospermins, new peptaibol antibiotics

The four homologous chrysospermins (Ia-d) are new 19 amino acid peptaibols which form cation selective ion channels in artificial lipid bilayer membranes. Conductance of channels formed by chrysospermins B (Ib) and D (Id) was twice as high (640 pS in 100 mM KCl) as found with chrysospermins A (Ia) and C (Ic). Single channel current traces were recorded for each of the four peptides even at very low (even zero) membrane voltages suggesting that non-gated channels are formed.

Aurantimycins, new depsipeptide antibiotics from Streptomyces aurantiacus IMET 43917. Production, isolation, structure elucidation, and biological activity

Aurantimycins A (1), B (2) and C (3) were isolated from the mycelium of Streptomyces aurantiacus JA 4570 as new representatives of the azinothricin group of hexadepsipeptide antibiotics. Their structures were settled by X-ray diffraction analysis of crystalline aurantimycin A (1), high field homo- and heteronuclear 2D NMR experiments, high-resolution mass spectrometry and amino acid analysis. Aurantimycins are characterized by a new side chain containing fourteen carbon atoms. They display strong activity against Gram-positive bacteria and cytotoxic effects against L-929 mouse fibroblast cells.

Advances in bioconversion of anthracycline antibiotics

During the last decade new anthracycline-type structures with potential usefulness in cancer treatment have been supplied both by new microbial strains and by bioconversions of precursor molecules employing cells or enzymes. We highlight recent advances in bioconversion of anthracycline structures with the main focus on late transformations such as are carried out by oxidoreductases.

Compartmentation of enzymes interconverting aclacinomycins in Streptomyces species AM 33352

The enzymatic interconversion of the aclacinomycins A (I), Y (II), and B (III) by Streptomyces spec. AM 33352/S 182 producing these aklavinone glycosides was investigated. The enzymes converting I to II and III, as well as vice versa, are located within different compartments separated by the cytoplasmic membrane. Aclacinomycin A (I) is biotransformed to II and III by the cell-free mycelium extract while the entire mycelium carries out the same type of conversion towards the opposite direction. Changes of enzyme activity are correlated to alterations in the ratio of aklavinone glycosides throughout the fermentation. A hypothesis is developed concerning the role of compartmentized oxidoreductase(s) in the passive flux of I from inside the cells to outside.

Inhibitors of the cleavage of aclacinomycins

The reductive cleavage of the aclacinomycins A (I), Y (II), and B (III) by intact mycelia or subcellular fractions of the producer strain S. spec. AM 33352/F43 is suppressed in the presence of uncouplers, complex-forming agents, detergents, and some metal anions such as chromate. Increased concentration of the latter in complete cultures caused rearrangement of I to III.

[The potential antineoplastic acting constituents of Physalis alkekengi L. var franchetii Mast]

In a continuing search for potent antineoplastic compounds in indigenous plants, a water extract of Physalis alkekengi L. var. franchetii Mast. fruits was shown to have reproducible antineoplastic activity against Ehrlich ascites carcinoma in mice. Systematic fractionation of the extract led to the isolation of citric acid as the major active principle.

Microbial conversion of daunorubicin into N-acetyl-13(S)-dihydrodaunomycin and bisanhydro-13-dihydrodaunomycinone

By using a strain of Streptomyces willmorii, daunorubicin (daunomycin) was stereoselectively converted into N-acetyl-13(S)-dihydrodaunomycin and bisanhydro-13-dihydrodaunomycinone. The absolute stereochemistry of the new chiral center in N-acetyl-13(S)-dihydrodaunomycin was established by means of nuclear Overhauser effect measured in the 9,13-O-isopropylidene derivative.

[Screening for antimicrobial and presumed cancerostatic plant metabolites (author's transl)]

693 kinds of indigenous plants randomly selected were screened for their antimicrobial activities against 23 different test organisms (Gram-positive, Gram-negative bacteria, yeast and fungi). The results of the testing showed that 250 (36%) kinds of the plants belonging to 72 families exhibited some level of antimicrobial action in vitro. Moreover, a microbiological prescreening program was employed in search of presumed cancerostatic plant products in crude extracts. These microbial tests based on agar diffusion techniques consist of prophage induction test and BIP test (bacteria inhibition-induction-phage inhibition). All active components selected by these microbial models are potential inhibitors of nucleic acid metabolism. A wide variety of plants was demonstrated to exhibit interesting activities in these screening systems. The bioactivity is uniformly distributed in various order. The screening results are briefly discussed.

Antimicrobial activities of daunorubicin and adriamycin derivatives on bacterial and protoplast type L-form cells of Bacillus subtilis 170, Escherichia coli B, and Proteus mirabilis VI. Structure--activity relationship

The antibacterial activity of ten N-alkylated derivatives of daunorubicin and adriamycin as well as of 5-iminodaunorubicin has been tested by using Bacillus subtilis 170, Escherichia coli B, and Proteus mirabilis VI and their stable protoplast type L-forms in an agar diffusion test. Eight of the substances showed similar activities against B. subtilis and the L-forms of all test organisms, but no activity against the bacterial forms of E. coli and P. mirabilis. The cell wall of these gram-negative bacteria is responsible for this resistance by not allowing the antibiotics to enter the cells. The piperidino compound N-(CH2)5 daunorubicin shows 2-4 times higher activity against B. subtilis and all L-forms in comparison to daunorubicin and the other derivatives. Five of the substances were inactive against all test strains. Their inactivity seems to be associated with the larger substituents at the C-3' position. Relations between molecular structure and activity are discussed considering data about the interaction with DNA and the antitumor activity. Stable protoplast type L-forms and their bacterial forms represent a suitable and effective test system to screen for more effective substances and to get more information about their mode of action.

Isolation and structures of nitrogen-free platenolide glycosides. I. The 5-O-(deoxy-3'-C-acetyl-beta-D-hexopyranosyl)-platenolides I and II

Four novel nitrogen-free glycosides of platenolides I and II were isolated as secondary shunt metabolites of the turimycin biosynthesis from the culture broth of an industrial strain of Streptomyces hygroscopicus IMET JA 6599. By spectral (MS, 1H and 13C NMR) studies the structures of the glycosides have been settled as 5-O-(4',6'-dideoxy-3'-C-acetyl-beta-D-hexopyranosyl)-platenolide I (DDAH-Pl-I), 5-O-(4',6'-dideoxy-3'-C-acetyl-beta-D-hexopyranosyl)-platenolide II (DDAH-Pl-II), 5-O-(4',6'-dideoxy-3'-C-acetyl-beta-D-hexopyranosyl)-14-hydroxyl-platenolide II (DDAH-OH-Pl-II) and 5-O-(6'-deoxy-3'-C-acetyl-beta-D-hexopyranosyl)-platenolide II (DAH-Pl-II). A fifth glycoside, 5-O-(6'-deoxy-3'-C-acetyl-beta-D-hexopyranosyl)-platenolide I (DAH-Pl-I) was identified through its MS data.

Isolation and structures of nitrogen-free platenolide glycosides. II. The 5-O-(alpha-mycarosyl)- and 5-O-(3'-demethyl-beta-mycaroxyl)-platenolides I and II

Three novel glycosides of platenolides I and II containing either mycarose (2,6-dideoxy-3-C-methyl-L-ribohexopyranose) or 3-demethyl-mycarose (2,6-dideoxy-L-ribohexopyranose) were isolated as the shunt products of turimycin biosynthesis by an industrial strain of Streptomyces hygroscopicus IMET JA 6599. By means of MS, 13C and 1H NMR spectroscopic studies, their structures were assigned as 5-O-(alpha-mycarosyl)-platenolide I (MYC-Pl-I), 5-O-(alpha-mycarosyl)-platenolide II (MYC-Pl-II) and 5-O-(3'-demethyl-beta-mycarosyl)-platenolide II (DM-MYC-Pl-II). The occurrence of 3-demethyl-mycaroside amongst the shunt metabolites is discussed in terms of its biosynthesis.

Griseorubins, a new family of antibiotics with antimicrobial and antitumor activity. II. Biological properties and antitumor activity of the antibiotic complex griseorubin

The antibiotic complex griseorubin has antimicrobial activity against Gram-positive as well as -negative bacteria, mycobacteria, mycoplasma and protozoa in vitro but it is not active against yeast and fungi. Tests with transplantable rodent tumors indicate that griseorubin is inhibitory to the growth of lymphatic leukemia L1210 in mice and Zajdela ascites hepatoma in rats. The acute LD50 of griseorubin in mice is 50 mg/kg of body weight when given intraperitoneally. Attempts to potentiate the antitumor activity by complexing with DNA proved to be unsuccessful.

Griseorubins, a new family of antibiotics with antimicrobial and antitumor activity. I. Taxonomy of the producing strain, fermentation, isolation and chemical characterization

A new antibiotic complex has been obtained from the cultures of Streptomyces strain No. IMET 20978 isolated from the shrimp Crangon crangon L. On the basis of taxonomic studies the producing microorganism is described as Streptomyces fimicarius (Duché) Waksman et Henrici, 1948, type strain IMET 20978. The antibiotic complex, designated as griseorubin, belongs to the polycyclic C-glycosyl antibiotics. It is a red-coloured amorphous material which consists of eight closely related fractions including griseorubins A, B, C, D, E, F, G, and H. The griseorubin complex exhibits antibiotic activity against Gram-positive and -negative bacteria as well as against mycoplasma and protozoa. The griseorubin complex is also effective on leukemia L1210 AND Zajdela ascites hepatoma.

[Search for nucleic acid influencing, as well as membrane active, potential cancerostatic fungal metabolites using microbiological and cytological screening methods]

A prescreening program including microbiological and cytological assays was employed in search of potential cancerostatic antibiotics in crude extracts of mushrooms. The microbiological tests based on agar diffusion techniques consist of prophage induction test and BIP-test. All active compounds selected by these microbiological models are potential inhibitors of nucleic acid metabolism. Cytological assays on leukemia L 1210 cells have been carried out by microscopic examination and by evaluation using an electronic particle counter. Activity was expressed as decrease of the number of single cells caused by agglutination or lysis of cells, changes in cell surface area, dye exclusion, and increase of cell volume. A wide variety of mushrooms was demonstrated to exhibit interesting activities in some of these screening systems. The influence of primary metabolic products of mushrooms on microbiological models was studied additionally. In vivo assays have not yet been accomplished.