Mass spectral investigation of fungal metabolites from Aspergillus ruber

Abstract

Thirteen samples isolated by silica gel chromatography from Aspergillus ruber grown on ground peanut slurries* were subjected to analysis with a high-resolution mass spectrometer. When sufficient amounts of sample were present, supportive techniques including NMR, IR, and UV spectroscopy were also employed. Thin-layer-chromatography was initially used to monitor the purity of the samples. However, mass spectrometric analysis showed the presence of two or more components in many of the fractions. Several of these multi-component samples were subjected to further purification by recrystallization, molecular distillation, or high-pressure liquid chromatography. High-resolution measurements on molecular ions permitted elemental compositions to be calculated for many of the components. Two of the compositions were supported by elemental analysis with a CHN analyzer. From the elemental compositions together with fragmentation patterns plus information from NMR, IR, and UV, molecular structures were proposed. Where certain functional groups were suspected, such as hydroxyl and amine moieties, chemical derivatizations including permethylation, demethylation, acetylation, oxidation, and reduction were carried out. Mass spectra were then obtained of the products. The reactions were also run on several standard compounds to check the experimental procedures and the predictability of the products..