Effect of the ultrasound-assisted extraction parameters on the determination of ergosterol and vitamin D2 in Agaricus bisporus, A. bisporus Portobello, and Pleurotus ostreatus mushrooms

Ergosterol is an important secondary metabolite precursor of vitamin D2 in mushrooms and is responsible for various health-promoting effects. The increasing interest in searching and analyzing foods rich in provitamin and vitamin D requires the optimization of a fast and effective extraction method. The comprehensive optimization of the parameters influencing ultrasound-assisted extraction (U.A.E) was performed to determine the best U.A.E conditions for ergosterol and vitamin D in mushrooms. The highest extraction yields were obtained with ethanol as solvent, 20 mg/mL as the solid-solvent ratio (SSR), at a frequency of 40 kHz, and a power of 240 W, for 30 min at 40 °C. For conjugated ergosterol, U.A.E in basic conditions (pH 11 using an ethanolic solution of KOH) at 60 °C for 30 min was ideal. Moreover, saponification after U.A.E did not provide any improvement on the extraction yield. The developed U.A.E. methods were applied on three mushroom species obtaining high levels of total ergosterol for Agaricus bisporus (6.8 ± 0.1 mg/g dw), A. bisporus Portobello (7.3 ± 0.2 mg/g dw), and Pleurotus ostreatus (4.9 ± 0.1 mg/g dw). Moreover, good levels of vitamin D2 (13.9–19.2 mg/100 g dw) in mushrooms were obtained after ultraviolet-C (UV-C) irradiation.