Identification and quantification of ergothioneine in cultivated mushrooms by liquid chromatography-mass spectroscopy

L-ergothioneine is a naturally occurring antioxidant that is available from dietary sources. There is a lack of an adequate assay applicable to identify and quantify this antioxidant in plant material. Thus, the objective was to identify and quantify the ergothioneine content of mushrooms including Agaricus bisporus (white and brown strains), Lentinus edodes, Pleurotus ostreatus, P. eryngii, and Grifola frondosa by an analytical method utilizing a high-performance liquid chromatography and liquid chromatography-mass spectroscopy. Freeze dried mushroom powder was analyzed with two C18 columns in tandem utilizing an isocratic mobile phase consisting of an aqueous sodium phosphate buffer with 3% acetonitrile and 0.1% triethylamine. Ergothioneine was identified by matching the retention time and mass spectra of the authentic compound with the mushroom samples, while quantification was completed via absorbance at 254 nm. The ergothioneine content of the mushrooms ranged from 0.4-2.0 mg/g (dry wt). The white Agaricus bisporus contained the least ergothioneine and portabellas (brown) contained the highest within the varieties of A. bisporus. The specialty mushrooms tested (Lentinus edodes, Pleurotus ostreatus, P. eryngii, Grifola frondosa) all contained a statistically significant greater amount of ergothioneine compared to the A. bisporus; however, no significant difference was found between these specialty mushrooms.