Identification and Determination of Rubrofusarin, Rubrofusarin Isomer, and Their Quinone Forms in Grains Using High-Resolution Mass Spectrometry

Theoretical modelling of structure, vibrational and UV-vis absorbance spectra of rubrofusarin molecule

The structure of the rubrofusarin molecule (CAS: 3567-00-8, IUPAC name 5,6-dihydroxy-8-methoxy-2-methyl-4H-benzo[g]chromen-4-one, molecular formula C₁₅H₁₂O₅) and its possible rotational conformers and tautomer were investigated within DFT approach. It was noted that for a stable molecules the group symmetry is close to Cs. The smallest potential barrier for rotational conformers is associated with the methoxy group rotation. The rotation of hydroxyl groups leads to a stable states that are substantially higher in energy than the ground state. Modeling and interpretation of vibrational spectra for the case of the ground state molecule in the gas phase and methanol solution was carried out, the influence of the solvent is discussed. The modelling of electronic singlet transition within the TD-DFT approach and the interpretation of obtained UV-vis absorbance spectra were carried out. A relatively small shift in the two most active absorption bands wavelength takes place for methoxy group rotation conformer. At the same time the redshift of the HOMO-LUMO transition takes place for this conformer. Much larger long wavelength shift of the absorption bands was noted for the tautomer.

Fungal quinones: diversity, producers, and applications of quinones from Aspergillus, Penicillium, Talaromyces, Fusarium, and Arthrinium

Quinones represent an important group of highly structurally diverse, mainly polyketide-derived secondary metabolites widely distributed among filamentous fungi. Many quinones have been reported to have important biological functions such as inhibition of bacteria or repression of the immune response in insects. Other quinones, such as ubiquinones are known to be essential molecules in cellular respiration, and many quinones are known to protect their producing organisms from exposure to sunlight. Most recently, quinones have also attracted a lot of industrial interest since their electron-donating and -accepting properties make them good candidates as electrolytes in redox flow batteries, like their often highly conjugated double bond systems make them attractive as pigments. On an industrial level, quinones are mainly synthesized from raw components in coal tar. However, the possibility of producing quinones by fungal cultivation has great prospects since fungi can often be grown in industrially scaled bioreactors, producing valuable metabolites on cheap substrates. In order to give a better overview of the secondary metabolite quinones produced by and shared between various fungi, mainly belonging to the genera Aspergillus, Penicillium, Talaromyces, Fusarium, and Arthrinium, this review categorizes quinones into families such as emodins, fumigatins, sorbicillinoids, yanuthones, and xanthomegnins, depending on structural similarities and information about the biosynthetic pathway from which they are derived, whenever applicable. The production of these quinone families is compared between the different genera, based on recently revised taxonomy. KEY POINTS: • Quinones represent an important group of secondary metabolites widely distributed in important fungal genera such as Aspergillus, Penicillium, Talaromyces, Fusarium, and Arthrinium. • Quinones are of industrial interest and can be used in pharmacology, as colorants and pigments, and as electrolytes in redox flow batteries. • Quinones are grouped into families and compared between genera according to the revised taxonomy.