Brevianamide L

In the present study, nine compounds (1-9) were isolated from Colletotrichum gloeosporioides (an endophytic fungus from Uncaria rhynchophylla) which was cultured in wheat bran medium. Their structures were elucidated as 4-Epi-14-hydroxy-10, 23-dihydro-24, 25-dehydroaflavinine (1), 10, 23-Dihydro-24,25 -dehydro-21-oxoaflavinine (2), Ergosterol (3), Ergosterol peroxide (4), Mellein (5), 4, 5-dihydroblumenol A (6), Colletotrichine A (7), Cyclo(L-leucyl-L-leucyl) (8), and Brevianamide F (9) based on NMR spectral data, as well as comparing with previous literature data. This is the first report about the isolation of compounds 1-2, 6, and 8-9 from Colletotrichum genus. All compounds were tested for their phosphoinositide 3-kinase (PI3Kα) inhibitory activity. Compounds 8 and 9 showed potent PI3K α inhibitory activity with IC50 values of 38.1 and 4.8 µM, respectively, while the other compounds showed very weak activity at a concentration of 20 µg/mL.

The fungal indole prenyltransferase FtmPT1 is involved in the biosynthesis of fumitremorgins and catalyzes, in the presence of dimethylallyl diphosphate, a predominant regular prenylation of cyclo-L-Trp-L-Pro (brevianamide F) at position C-2 of the indole nucleus. Analysis of the substrate-bound structure of FtmPT1 revealed that brevianamide F forms a hydrogen bond via its carbonyl oxygen in the diketopiperazine moiety with the hydroxyl group of Tyr205 near the center of the prenyltransferase (PT) barrel. In this study, Tyr205 was mutated to 19 other proteinogenic amino acids by one-step site-directed mutagenesis. The obtained mutants were assayed in the presence of dimethylallyl diphosphate with brevianamide F. The enzyme products were isolated on HPLC and their structures were elucidated by NMR and MS analyses. Mutation of Tyr205 to Phe or Met did not change the behavior of FtmPT1 significantly, with regularly C2-prenylated brevianamide F as the predominant product. Interestingly, 15 of the obtained mutants also produced regularly C3-prenylated brevianamide F, with relative yields between 33 and 110 % of those of the regularly C2-prenylated derivatives. Among them, Y205C, Y205L, Y205N, Y205I, and Y205S showed similar brevianamide F consumption. Y205H, Y205Q, Y205V, Y205G, and Y205E showed activities between 47 and 77 % of that of the wild type. These results provide a solid basis for the construction of a brevianamide F regular C3-prenyltransferase by site-directed mutagenesis. Assaying stereoisomers of brevianamide F, cyclo-D-Trp-D-Pro, cyclo-L-Trp-D-Pro, and cyclo-D-Trp-L-Pro, with two selected mutants Y205N and Y205L resulted in the formation of reversely C3-prenylated derivatives as predominant products, being in sharp contrast to their regularly C2- and C3-prenylated derivatives with cyclo-L-Trp-L-Pro.

The aim of this explorative study was to investigate how effective drying preservation methods are in reducing mycotoxin content in figs. Dried autochthonous varieties of white and dark figs (Petrovača Bijela and Šaraguja, respectively) were analysed for mycotoxins using an LC-MS/MS "dilute and shoot" method capable of determining 295 fungal and bacterial secondary metabolites. Before drying in a cabinet dryer the figs were preserved with 0.5 % citric acid solution or 0.5 % ascorbic acid solution or 0.3 % L-cysteine solution or 0.2 % chestnut extract solution or 0.15 % Echinacea extract solution by immersion. We found nine metabolites: aflatoxin B1 (AFB1), ochratoxin A, ochratoxin alpha, kojic acid, emodin, altenuene, alternariol methyl ether, brevianamide F, and tryptophol. The most efficient preserver was L-cysteine (15 % reduction), while ascorbic acid favoured mycotoxin production (158 % increase). However, all pretreatment solutions reduced AFB1, which is a major fig contaminant.