Vitamin D-enriched extracts obtained from shiitake mushrooms (Lentinula edodes) by supercritical fluid extraction and UV-irradiation

•Fractions containing up to 18% ergosterol can be obtained by SFE from L. edodes.•UV-irradiation of ergosterol-enriched fractions generated vitamin D-enriched extracts.•Transformation was enhanced when SFE extracts were dissolved in organic solvents.•Wide Spectrum- and UV-C irradiation without heat were more effective than UV-A.

The combination of supercritical fluid extraction followed by UV-irradiation resulted in an interesting strategy to obtain ergosterol- and Vitamin D2-enriched extracts from Lentinula edodes to design novel functional food. Extractions carried out following a specific experimental design pointed out that extraction yields and ergosterol concentrations were more influenced by pressure than by the extraction temperature although, high temperatures (55-75 °C) might induce transformation of ergosta-7,22-dienol and fungisterol into ergosterol. After extraction, the ergosterol-enriched extracts should be dissolved in methanol or ethanol and irradiated (25 °C, 4 cm) to partially transform ergosterol into vitamin D2. Irradiation at 365 nm was less effective than at 254 nm. The fastest transformation was obtained using a UV lamp covering the complete UV spectrum for a maximum of 1 h. However, this lamp also induced vitamin D4 formation although in lower amounts than vitamin D2 or lumisterol2 while with irradiation at 254 nm most of ergosterol was transformed into vitamin D2.