Aspochalamins A-D, a family of new cytochalasan antibiotics have been isolated from Aspergillus niveus, an endosymbiotic fungus isolated from the gut of a woodlouse belonging to the family Trichoniscidae. Besides aspochalamins, aspochalasin Z, a new member of the aspochalasin family, as well as the known mycotoxins aspochalasin D and citreoviridins A/C and B were isolated from the mycelium. Aspochalamins showed cytostatic effects towards various tumor cell lines and a weak antibacterial activity against Gram-positive bacteria.
The structures of new cytochalasan fungal metabolites aspochalamins A-D have been elucidated by ESI-FTICR-MS, NMR spectroscopy, and chiral amino acid analysis. Aspochalamins A-D consist of different aspochalasin skeletons connected at position C-19 to the N terminus of the tripeptidic moiety amide anthranoyl-L-alanine-E-didehydrotryptamide. Furthermore, the structure of a new aspochalasin analog, aspochalasin Z, was derived from its molecular mass and NMR data as 10-isopropyl-14-methyl-cytochalasa-6Z, 13E, 19E-triene-1, 21-dione.
Two new illudane sesquiterpenes, paneolic acid and paneolilludinic acid, along with a known antibiotic diterpene, pleuromutilin, were isolated from the mycelial solid cultures of Panaeolus retirugis. Their structures were elucidated on the basis of spectroscopic analysis. Both compounds exhibited antibacterial activity against Staphylococcus aureus, and paneolic acid showed cytotoxicity to HL60 cell with an IC50 of 18.9μg/ml.
In the course of screening for biological active compounds from microbial origins, various strains were isolated from roots of Mimosa pudica using standard dilution agar plate method. One isolate was selected for further studies of bacterial anti-fungal properties. It was designated MSSP and identified as Burkholderia sp. by many biological characteristics such as carbohydrate utilization, biochemical and physiological test and 16S rDNA sequence homology search. To investigate antagonistic principle, anti-fungal compounds were extracted and fractionated by different solvent systems. An anti-fungal compound was isolated from its culture filtrate using organic solvent extraction, column chromatography and thin layer chromatography and pure solid form compound (MSSP2) was obtained. The chemical structure of anti-fungal compound was identified as 2-Hydroxymethyl-chroman-4-one based on the data obtained from spectroscopic analysis such as mass spectral analyses and NMR spectral data. The compound 2-Hydroxymethyl-chroman-4-one exhibited good activities against phytopathogen such as Pythium ultimum, Phytophthora capsici and Sclerotinia sclerotiorum.
Optimal fermentation conditions for enniatin production using the entomopathogenic fungus Verticillium hemipterigenum BCC 1449 have been investigated. Among various liquid media tested, highest efficiency of enniatin production was achieved by fermentation in yeast extract sucrose. Application of this condition to large-scale fermentation resulted in the isolation of three new analogs, O1, O2 and O3, which are closely related isomers that were characterized as an inseparable mixture, along with seven known enniatins.
We have previously shown that gene clusters for biosyntheses of terpentecin and BE-40644, a diterpene antibiotic and a sesquiterpene antibiotic, respectively, were located in the adjacent mevalonate pathway gene clusters. In this study, a mevalonate pathway gene cluster was cloned from Streptomyces sp. strain KO-3988, which was known to produce furaquinocin A, employing a hybridization experiment using a 3-hydroxy-3-methyl glutaryl CoA (HMG-CoA) reductase gene, which had been previously cloned from the strain KO-3988, as a probe. By sequencing flanking regions, we found four open reading frames that could encode a putative cytochrome P450 (ORF1), an isoprenoid cyclase (ORF2), an unknown protein (ORF3), and a polyprenyl diphosphate synthase gene (ORF4) in the upstream region of the mevalonate pathway gene cluster, though we did not find any genes related to furaquinocin A biosynthesis. The two ORFs (ORF2 and 4) were expressed as recombinant enzymes in E. coli and used for studies to investigate functions of these products. The ORF4 product was confirmed to be a geranylgeranyl diphosphate (GGDP, C20) synthase. The ORF2 product proved to catalyze a conversion of GGDP into copalyl diphosphate, the first example of an enzyme with this function of prokaryotic origin. These results again showed that actinomycetes possessing the mevalonate pathway usually produce an isoprenoid and that its biosynthetic gene cluster exists in adjacent the mevalonate pathway gene cluster.
Aspergillus fumigatus TP-F0196 produces pseurotin A, synerazol and gliotoxin. Phenylalanine is a common biosynthetic precursor of these antibiotics. Feeding fluorophenylalanine to the culture induced the production of novel fluorinated analogs. These fluorinated antibiotics were obtained from the culture broth by solvent extraction and purified by chromatographies, and their antimicrobial and antitumor activities were investigated. Among the novel fluorinated analogs, 19- and 20-fluorosynerazols exhibited potent anti-angiogenic activity in the chorioallantoic membrane assay. In addition, 19-fluorosynerazol showed more potent cytocidal activity against several cancer cell lines than synerazol.