Metabolomic discrimination of the edible mushrooms Kuehneromyces mutabilis and Hypholoma capnoides (Strophariaceae, Agaricales) by NMR spectroscopy.

Two edible, cultivable mushroom species of the family Strophariaceae, Kuehneromyces mutabilis (sheathed woodtuft) and Hypholoma capnoides (conifer tuft), were studied using proton nuclear magnetic resonance metabolomic approach. The variation in the metabolites of the two species and their metabolic behaviour regarding caps and stipes and different collection sites were analysed by multivariate analysis methods. Altogether 169 cap and stipe samples of the mushrooms were investigated. The clearest difference between the species was in the sugar composition, which was more diverse in H. capnoides. When mushroom samples collected from different locations were compared, more variance was found in H. capnoides, whereas K. mutabilis appeared more homogeneous as a species. As far as the caps and stipes were concerned, in both species the amount of α-α-trehalose was clearly higher in the stipes, and the caps contained a larger proportion of the amino acids and organic acids.

Suitability of dried herbarium specimens for NMR metabolomics of mushrooms. A comparison of four species of the genera Kuehneromyces and Hypholoma (Strophariaceae).

Herbarium specimens are a treasure trove for biochemical studies. However, this implies understanding of the chemical changes during the drying and storage of the specimen. We compared herbarium specimens at different ages and fresh samples of four mushroom species (Kuehneromyces mutabilis, Hypholoma capnoides, Kuehneromyces lignicola, Hypholoma fasciculare) of two genera in the family Strophariaceae by using proton nuclear magnetic resonance (1H NMR) spectroscopy combined with principal component analysis (PCA). 25 metabolites were identified. No significant alterations were found between herbarium samples at different ages, suggesting that they are stable enough for comparative studies. The most dominant differences between fresh and herbarium samples was that sugars such as α-α-trehalose, and fumaric and malic acids were more abundant in fresh fungi. Total contents of fatty and amino acids, uracil and γ-aminobutyric acid (GABA) were higher in herbarium specimens. In addition, pyroglutamic acid was observed only in Kuehneromyces mutabilis and fasciculic acid E in Hypholomafasciculare. Hence, based on results of the studied taxa, we conclude that NMR metabolomics can be used for both fresh and dried mushrooms when such alterations are properly addressed.