Effects of ortho-substituent groups of sulochrin on inhibitory activity to eosinophil degranulation

Sulochrins and alkaloids from a fennel endophyte Aspergillus sp. FVL2

The fungal endophyte Aspergillus sp. strain FVL2, isolated from the traditional medicinal fennel plant, Foeniculum vulgare, was investigated for secondary metabolites. Fermentation on rice medium followed by chromatographic separation delivered three new natural products, 7-demethyl-neosulochrin (1), fumigaclavine I (3) and N-benzoyl-tryptophan (6) together with further 14 known metabolites, 1-O-methyl-sulochrin-4'-sulfate, questin, laccaic acid, isorhodoptilometrin, fumigaclavine A, fumigaclavine C, fumitremorgin C, fumigaquinazoline C, tryptoquivaline J, trypacidin, 3'-O-demethyl-sulochrin, 1-O-methyl-sulochrin, protocatechuic acid, and vermelone. The chemical structures of the new metabolites were determined by NMR spectroscopy and ESI HR mass spectrometry. For fumigaclavine I, we observed the partial deuterium transfer from the solvent to the enol form with a remarkable high stereo selectivity. The discovery of the new seco-anthraquinone 7-demethyl-neosulochrin (1) revealed a second type of ring cleavage by a questin oxygenase. The discovery of diverse secondary metabolites broadens the chemical space of Aspergillus.

Sulfur-Containing Phenolic Compounds from the Cave Soil-Derived Aspergillus fumigatus GZWMJZ-152

Six new sulfur-containing phenolic compounds (1-6) and their putative metabolic precursors (7-9) were isolated from the cave soil-derived fungus Aspergillus fumigatus GZWMJZ-152. Compound 1 represents an unusual benzophenone-diketopiperazine hybrid via a thioether linker, while compound 2 contains a naturally rare sulfoxide group. Both compounds 2 and 3 were initially isolated as racemic mixtures and then purified as the enantiomerically pure (+)-2, (-)-2, (+)-3, and (-)-3, respectively. Their structures, including absolute configurations, were elucidated by spectroscopic analysis, X-ray diffraction, and the calculations of electronic circular dichroism. The antioxidant activity of compounds 1-9 was evaluated based on oxygen radical absorbance capacity, 2,2-diphenyl-1-picrylhydrazyl radical scavenging, and the protective effect on the PC12 cell line against H₂O₂-induced damage. Compounds 5-7 and 9 showed radical-scavenging activity against 2,2-diphenyl-1-picrylhydrazyl free radicals with the IC₅₀ values of 3.45 ± 0.02, 23.73 ± 0.08, 18.90 ± 0.16, and 17.27 ± 0.15 μM, respectively. Compounds (±)-2, 4, 7, and 8 exhibited potent antioxidant capacity with oxygen radical absorbance capacity values of 1.73 ± 0.13, 1.65 ± 0.03, 6.14 ± 0.35, and 1.55 ± 0.04 μmol TE/μmol, respectively. Compounds (±)-2 and (±)-3 also exhibited protective effects on oxidative injury of PC12 cells induced by H₂O₂.

Case-Control Study of Nodding Syndrome in Acholiland: Urinary Multi-Mycotoxin Screening

This case-control study adds to the growing body of knowledge on the medical, nutritional, and environmental factors associated with Nodding Syndrome (NS), a seizure disorder of children and adolescents in northern Uganda. Past research described a significant association between NS and prior history of measles infection, dependence on emergency food and, at head nodding onset, subsistence on moldy maize, which has the potential to harbor mycotoxins. We used LC-MS/MS to screen for current mycotoxin loads by evaluating nine analytes in urine samples from age-and-gender matched NS cases (n = 50) and Community Controls (CC, n = 50). The presence of the three mycotoxins identified in the screening was not significantly different between the two groups, so samples were combined to generate an overall view of exposure in this community during the study. Compared against subsequently run standards, α-zearalenol (43 ± 103 µg/L in 15 samples > limit of quantitation (LOQ); 0 (0/359) µg/L), T-2 toxin (39 ± 81 µg/L in 72 samples > LOQ; 0 (0/425) µg/L) and aflatoxin M1 (4 ± 10 µg/L in 15 samples > LOQ; 0 (0/45) µg/L) were detected and calculated as the average concentration ± SD; median (min/max). Ninety-five percent of the samples had at least one urinary mycotoxin; 87% were positive for two of the three compounds detected. While mycotoxin loads at NS onset years ago are and will remain unknown, this study showed that children with and without NS currently harbor foodborne mycotoxins, including those associated with maize.

Redundant synthesis of a conidial polyketide by two distinct secondary metabolite clusters in Aspergillus fumigatus

Filamentous fungi are renowned for the production of bioactive secondary metabolites. Typically, one distinct metabolite is generated from a specific secondary metabolite cluster. Here, we characterize the newly described trypacidin (tpc) cluster in the opportunistic human pathogen Aspergillus fumigatus. We find that this cluster as well as the previously characterized endocrocin (enc) cluster both contribute to the production of the spore metabolite endocrocin. Whereas trypacidin is eliminated when only tpc cluster genes are deleted, endocrocin production is only eliminated when both the tpc and enc non-reducing polyketide synthase-encoding genes, tpcC and encA, respectively, are deleted. EncC, an anthrone oxidase, converts the product released from EncA to endocrocin as a final product. In contrast, endocrocin synthesis by the tpc cluster likely results from incomplete catalysis by TpcK (a putative decarboxylase), as its deletion results in a nearly 10-fold increase in endocrocin production. We suggest endocrocin is likely a shunt product in all related non-reducing polyketide synthase clusters containing homologues of TpcK and TpcL (a putative anthrone oxidase), e.g. geodin and monodictyphenone. This finding represents an unusual example of two physically discrete secondary metabolite clusters generating the same natural product in one fungal species by distinct routes.

Aspergillus fumigatus CY018, an endophytic fungus in Cynodon dactylon as a versatile producer of new and bioactive metabolites

Aspergillus fumigatus CY018 was recognized as an endophytic fungus for the first time in the leaf of Cynodon dactylon. By bioassay-guided fractionation, the EtOAc extract of a solid-matrix steady culture of this fungus afforded two new metabolites, named asperfumoid (1) and asperfumin (2), together with six known bioactive compounds including monomethylsulochrin, fumigaclavine C, fumitremorgin C, physcion, helvolic acid and 5alpha,8alpha-epidioxy-ergosta-6,22-diene-3beta-ol as well as other four known compounds ergosta-4,22-diene-3beta-ol, ergosterol, cyclo(Ala-Leu) and cyclo(Ala-Ile). Through detailed spectroscopic analyses including HRESI-MS, homo- and hetero-nuclear correlation NMR experiments (HMQC, COSY, NOESY and HMBC), the structures of asperfumoid and asperfumin were established to be spiro-(3-hydroxyl-2,6-dimethoxyl-2,5-diene-4-cyclohexone-(1,3')-5'-methoxyl-7'-methyl-(1'H, 2'H, 4'H)-quinoline-2',4'-dione) and 5-hydroxyl-2-(6-hydroxyl-2-methoxyl-4-methylbenzoyl)-3,6-dimethoxyl-benzoic methyl ester, respectively. All of the 12 isolates were subjected to in vitro bioactive assays against three human pathogenic fungi Candida albicans, Tricophyton rubrum and Aspergillus niger. As a result, asperfumoid, fumigaclavine C, fumitremorgin C, physcion and helvolic acid were shown to inhibit C. albicans with MICs of 75.0, 31.5, 62.5, 125.0 and 31.5 microg/mL, respectively.