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

Abstract

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.