Investigation of Structural and Spectral Peculiarities of Fusarium sp. Indicator Pigment Bostrycoidin

Bostrycoidin is one of the pigments produced by the <i>Fusarium</i> genus of fungi. On the one hand, it has significant pharmacological importance, while on the other hand, it serves as a presence marker of Fusarium infection in useful grain crops, fruits, and soils. In this regard, the structural and optical properties of the bostrycoidin molecule were studied in the framework of density functional theory (DFT). The most stable geometry as well as higher-energy conformers and tautomers were investigated. The lowest-energy tautomer was found to be about 3 kcal/mol higher in energy than the most stable structure, resulting in relatively low population of this state. The obtained conformational rotamers associated with the rotation of the OMe group possess similar energy. The vibrational spectrum was modeled for the most stable conformer, and the most active peaks in the IR absorbance spectrum were assigned. Moreover, the electronic absorption spectrum was simulated within the time-dependent DFT approach. The obtained theoretical spectrum is in good agreement with the experimental data and the theoretically calculated longest-wavelength transition (HOMO-LUMO) was about 498 nm.