Bog bilberry (Vaccinium uliginosum L.) and the enigma of its alleged toxicity

Bog bilberry (Vaccinium uliginosum L.) is a species of wild-growing berry native to all circumboreal regions. Many locals across different European countries avoid the berries, listing headaches, vomiting, and hallucinations among the effects after consuming a large amount, whereas in North America and Asia they are picked and freely consumed without any fear. A review of the historical sources shows how the attitude of European nations evolved throughout the 20 ^th century. There are several case reports of poisonings by bog bilberry between 1906 and 1944; some of them can be elucidated but others remain unexplained. The hypotheses for the alleged toxicity include bilberry blight by Monilinia megalospora, rapid fermentation of the berries resulting in a significant alcohol content, individual allergy/intolerance, or differences in the metabolite profile in some European populations. In this study, samples of bog bilberries were collected from different European countries (Austria, Slovakia, Estonia, Finland, Norway), as well as Alaska. Since the non-polar constituents of bog bilberry are still underexplored, a dichloromethane extract was generated from the dried and defatted berries. An environmentally friendly supercritical fluid chromatography coupled with mass spectrometry was employed to evaluate the chemical composition of extracts. A high triterpenes content was identified in all screened samples, dominated by ursolic and oleanolic acids and their various derivatives. In the preliminary in vivo toxicity assay using the nematode model Caenorhabditis elegans, neither the dichloromethane nor the combined methanol-dichloromethane extract of bog bilberry fruits showed any nematotoxic effects. This is the first phytochemical screening of V. uliginosum fruits focusing on the non-polar constituents in relation to the alleged toxicity of bog bilberries. Further research is necessary to determine other possible causes for the assumed toxicity.