Previtamin D2, vitamin D2, and vitamin D4 amounts in different mushroom species irradiated with ultraviolet (UV) light and occurrence of structurally related photoproducts

Mushrooms are rich in ergosterol and ergosta-5,7-dienol, which can be partly converted into vitamin D₂ and D₄ through ultraviolet (UV) light exposure. Typically, mushrooms have very low vitamin D contents, but it can be increased by UV irradiation. This process generates additional photoisomers scarcely studied in mushrooms due to analytical challenges. Here, we developed a new solid phase extraction (SPE) method to separate vitamin D₂, vitamin D₄, and other tri- and pentacyclic photoisomers from the much higher abundant ergosterol. Subsequent GC/MS analysis enabled the detection of ten photoisomers in eight UV-treated mushroom species, including vitamin D₂ (previtamin D₂, tachysterol₂, two suprasterol₂ and trans-vitamin D₂ isomers) and vitamin D₄ (previtamin D₄). Quantitated vitamin D₂ contents of 10–540 µg/100 g dry weight agreed well with the sparse literature data available for the investigated mushroom species. In addition, previtamin D₂ (nd–1950 µg/100 g dry weight) and vitamin D₄ (10–140 µg/100 g dw) were quantified in the samples. The content and photoproduct compositions varied considerably between different mushroom species.

Practical applications: The novel SPE method can be applied to study the vitamin D and photoisomer content of mushrooms.