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.

Griseofulvin enantiomers and bromine-containing griseofulvin derivatives with antifungal activity produced by the mangrove endophytic fungus Nigrospora sp.QQYB1

Marine microorganisms have long been recognized as potential sources for drug discovery.Griseofulvin was one of the first antifungal natural products and has been used as an antifungal agent for decades.In this study,12 new griseofulvin derivatives[(±)-1-2,(+)-3,(±)-4,10-12,and 14-15]and two new griseofulvin natural products(9 and 16)together with six known analogues[(-)-3,5-8,and 13]were isolated from the mangrove-derived fungus Nigrospora sp.QQYB1 treated with 0.3%NaCl or 2%NaBr in rice solid medium.Their 2D structures and absolute configurations were established by extensive spectroscopic analysis(1D and 2D NMR,HRESIMS),ECD spectra,computational calculation,DP4+analysis,and X-ray single-crystal diffraction.Compounds 1-4 represent the first griseofulvin enantiomers with four absolute configurations(2S,6'S;2R,6'R;2S,6'R;2R,6'S),and compounds 9-12 represent the first successful production of brominated griseofulvin derivatives from fungi via the addition of NaBr to the culture medium.In the antifungal assays,compounds 6 and 9 demonstrated significant inhibitory activities against the fungi Colletotrichum truncatum,Microsporum gypseum,and Trichophyton mentagrophyte with inhibition zones varying between 28 and 41 mm(10μg/disc).The structure-activity relationship(SAR)was analyzed,which showed that substituents at C-6,C-7,C-6'and the positions of the carbonyl and double bond of griseofulvin derivatives significantly affected the antifungal activity.

(+)/(-)-Mycosphatide A,a pair of highly oxidized polyketides with lipid-lowering activity from the mangrove endophytic fungus Mycosphaerella sp.SYSU-DZG01

(±)-Mycosphatide A(1a/1b),a pair of highly oxidized enantiomeric polyketides featuring a unique5/5/6/5-fused tetracyclic ring system,were isolated from the mangrove endophytic fungus Mycosphaerella sp.SYSU-DZG01.Their structures were established by extensive spectroscopic analyses,single crystal Xray diffraction,and experimental electronic circular dichroism(ECD)spectra comparison.The plausible biosynthetic pathway of 1 was proposed,which involved the generation of a key spiro[4.5]decane scaffold.Compounds(+)-1a and(-)-1b exhibited significant lipid-lowering activity in 3T3-L1 adipocytes model,with EC50values of 7.85±1.56 and 8.87±0.80μmol/L,respectively.

Talaketides A-G,linear polyketides with prostate cancer cytotoxic activity from the mangrove sediment-derived fungus Talaromyces sp.SCSIO 41027

Seven novel linear polyketides,talaketides A-G(1-7),were isolated from the rice media cultures of the mangrove sed-iment-derived fungus Talaromyces sp.SCSIO 41027.Among these,talaketides A-E(1-5)represented unprecedented unsaturated lin-ear polyketides with an epoxy ring structure.The structures,including absolute configurations of these compounds,were elucidated through detailed analyses of nuclear magnetic resonance(NMR)and high-resolution mass spectrometry(HR-MS)data,as well as elec-tronic custom distributors(ECD)calculations.In the cytotoxicity screening against prostate cancer cell lines,talaketide E(5)demon-strated a dose-dependent inhibitory effect on prostate cancer PC-3 cell lines,with an IC50 value of 14.44 μmol·L-1.Moreover,com-pound 5 significantly inhibited the cloning formation of PC-3 cell lines and arrested the cell cycle in S-phase,ultimately inducing ap-optosis.These findings indicate that compound 5 may serve as a promising lead compound for the development of a potential treat-ment for prostate cancer.

Diversified Polyketides and Nitrogenous Compounds from the Mangrove Endophytic Fungus Penicillium steckii SCSIO 41025

Four new polyketide decalin derivatives,penicisteck acids A-D(1-4),and three new nitrogenous compounds(7-9)z together with eight previously reported compounds,were isolated from the mangrove endophytic fungus Penicillium steckii SCSIO 41025.

Crystal Structure of a Marine Natural Compound,Anhydrofusarubin

One marine natural compound, anhydrofusarubin, was isolated from the endophytic fungus No. B77 from the mangrove tree on the South China Sea coast. It was the first time that such a compound was isolated from marine fungus. The structure was identified by NMR data and mass spectrometry （MS）. In addition, its structure was determined by single-crystal X-ray diffraction analysis. It crystallizes in triclinic, space group P1^- with a = 8.3185（15）, b = 12.397（2）, c = 13.767（3） A, α = 65.692（3）, β = 79.266（3）, γ= 75.692（3）°, C15H12O6, Mr= 288.24, V = 1248.0（4） A^3, Z = 4, Dc = 1.534 g/cm^3, F（000） = 600, μ = 0.120 mm^-1, the final R = 0.0459 and wR = 0.1184 for 5360 observed reflections （I 〉 2σ（I））. In the primary bioassay, the title compound shows strong inhibitory activity against Gram-positive bacteria Staphyococcus aureus （ATCC27154） with the MIC value of 12.5 μg/mL.