Single-run analysis of vitamin D photoproducts in oyster mushroom (Pleurotus ostreatus) after UV-B treatment

A single-run high performance liquid chromatography (HPLC) with diode array detector (DAD) based method was developed for the separation, identification and comprehensive quantification of degradation products of ergosterol formed in oyster mushroom (Pleurotus ostreatus) after UV-B exposure. After 60 min, 10 substances involved in the photoprocess were separated, identified by their characteristic DAD spectrum and distinguished by their molecular weight, in cases where spectra were identical: vitamin D₂, previtamin D₂, tachysterol₂, lumisterol₂ and ergosterol, and, in minor quantity, their structural analogues of the 22,23-dihydroergocalciferol (vitamin D₄) series. Sample preparation protocol affected the total yields and the ratios of previtamin and vitamin D₂/D₄. Hot alkaline hydrolysis resulted in the best digestion of the mushroom matrix and accordingly gave the highest vitamin D yield (D₂: 141.32 μg g^?1 dry matter, DM; D₄: 22.72 μg g^?1 DM). Limit of detection for vitamin D_2/4 was 0.02 μg g^?1 dry matter (DM) and was estimated for previtamin D_2/4 (0.06 μg g^?1 DM), tachysterol_2/4 (0.02 μg g^?1 DM) and lumisterol_2/4 (0.06 μg g^?1 DM). Recovery of spiked vitamin D₂ was 97 ± 0.7%. The study provides an analytical tool to assess the process of vitamin D generation after UV-B treatment for the production of oyster mushrooms with a balanced nutritional profile of vitamin D compounds.