High levels of the health-relevant antioxidant selenoneine identified in the edible mushroom Boletus edulis.

Background: Selenoneine, the selenium analogue of the sulfur antioxidant ergothioneine, has been ascribed a multitude of beneficial health effects. Natural nutritional sources for this selenium species are, hence, of high interest. So far marine fish is the only significant selenoneine source consumed by larger parts of the population worldwide.

Methods: As selenoneine and ergothioneine share their biosynthetic pathways and transport mechanisms and the popular edible porcini mushroom Boletus edulis is rich in ergothioneine and selenium, we conducted a preliminary study investigating a composite sample of two specimens of B. edulis for their selenoneine content by HPLC coupled to elemental and molecular mass spectrometry after aqueous extraction.

Results: Selenium speciation analysis by HPLC-ICPMS revealed that ca. 860 µg Se kg wet mass (81 % of the total Se) co-eluted with a selenoneine standard and a minor selenium species with Se-methylselenoneine. The presence of selenoneine was rigorously proven by HPLC-ESI-Orbitrap MS. The selenoneine content of the investigated specimens of B. edulis was higher than that of commonly consumed muscle of marine fish species, like tuna or mackerel.

Conclusion: This is the first report of a terrestrial food source containing significant selenoneine levels. Our results suggest that B. edulis might represent a complementary natural supply with this health-relevant selenium species for humans.