Analysis of indole compounds in edible Basidiomycota species after thermal processing

Abstract

Methanolic extracts of processed fruiting bodies of six edible mushroom species (Basidiomycota) –Armillaria mellea, Boletus badius, Boletus edulis, Cantharellus cibarius, Lactarius deliciosus collected from natural habitats and Pleurotus ostreatus of commercial origin – were analysed for the presence of non-hallucinogenic indole compounds. Thermal processing was designed in such a way that it mimicked conditions used for cooking of mushroom dishes, since only a narrow group of mushrooms can be eaten raw, while indole compounds are thermolabile. All processed extracts were shown to contain l-tryptophan (up to 8.92mg/100g dw). The contents of the remaining compounds, 5-methyltryptophan, tryptamine, melatonin, indoleacetonitrile and indole, varied in different species (from 0.71 to 6.55mg/100g dw). Extract of processed C. cibarius fruiting bodies contained l-tryptophan, 5-methyltryptophan, tryptamine, melatonin, indoleacetonitrile and indole (1.96–4.94mg/100g dw) whereas l-tryptophan (2.78mg/100g dw) and tryptamine (2.77mg/100g dw) were the only indole compounds identified in the processed fruiting bodies of A. mellea.