Antifungal Secondary Metabolites Isolated from Mangrove Rhizosphere Soil-Derived Penicillium Fungi

Fungi isolated from mangrove rhizosphere soil of the South China Sea were investigated for the production of potential antifungal metabolites. With 28 fungal isolates, the strains Penicillium javanicum HK1-23 and P. janthinellum HK1-6 showed significant antifungal activities. A bioassay-guided investigation of the two fungal strains led to the isolation of two secondary metabolites, brefeldin A and penicillic acid, with high yields of 143 and 423 mg L^-1, respectively. Penicillic acid showed potent antifungal activities toward Rhizoctonia solani and R. cerealis, with 67.5% and 76% growth inhibition, respectively, at 50 μg mL^-1. Brefeldin A showed strong activity toward R. cerealis, with 56.4% growth inhibition at 50 μg mL^-1. The research highlights the importance of exploring microbes from mangrove rhizosphere soil for the identification of bioactive metabolites for future fungicide development.

A set of interesting sequoiatones stereoisomers from a wetland soil-derived fungus Talaromyces flavus

Four interesting sequoiatones stereoisomers(1-4) were isolated from a wetland soil-derived fungus Talaromyces flavus by chiral HPLC.On the basis of comprehensive NMR and mass analyses,their planar structures were elucidated as the same as that of sequoiatone B.Among them,1 and 3(or 2 and 4)were a pair of enantiomers,and 1 and 2(or 3 and 4) were a pair of stereoisomers with epimerization at C-12,which indicated that sequoiatione-type metabolites exist as enantiomers rather than as optically pure compounds in some strains.With the quantum chemical ECD calculations,the absolute configurations of C-8 in 1-4 were determined,which is the first report to establish the absolute configuration of C-8 in sequoiatones.However,the absolute configurations of C-12 in sequoiatones are still unsolved.

New secondary metabolites with cytotoxicity from fungus Penicillium roqueforti

Two novel compounds including a cyclohelminthol type polyketide(namely oxaleimide K,1)and a maleimide deriva-tive(namely peniroquefortine A,2),and a new natural product(namely 2-(acetylamino)-N-[(1E)-2-phenylethenyl]-acetamide,3),together with four known compounds(4-7),were isolated and identified from fungus Penicillium roqueforti,which was separated from the root soil of Hypericum beanii N.Robson collected from the Shennongjia For-estry District,Hubei Province.Their structures including absolute configurations were mainly established by the NMR spectroscopy analyses and single-crystal X-ray diffraction experiment.Compound 1 represents the second example of a cyclohelminthol type polyketide,which features a rare 6/6/5/5 tetracyclic system and a branched aliphatic chain containing a terminal olefin(oct-1-en-3-yl)moiety,and compound 2 possesses an unprecedented carbon skeleton that is uniquely defined by a maleimide moiety linked to the respective 4-methylene-2-(3-methylbut-2-en-1-yl)-phenol and para-substituted aromatic moieties via the carbon-carbon bonds.Remarkably,the absolute configuration of a cyclohelminthol type polyketide as exemplified by compound 1 is determined by the single-crystal diffraction analysis for the first time,highlighting an E-configuration for the linkage of a succinimide moiety and a tetrahydro-furan moiety for 1 rather than a Z-configuration as previously reported in the biosynthesis study,which gives a new insight into the structural elucidation of this category of polyketides.Additionally,compound 1 exhibited significant cytotoxic activity against multiple tumor cells,especially against the Farage and SU-DHL-2 cells(IC_(50)<20μM,48 h).Further mechanism study revealed that compound 1 significantly induced cell cycle arrest in Farage and SU-DHL-2 cells by causing abnormal ROS level and triggering oxidative stress.