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

The combination of supercritical fluid extraction followed by UV-irradiation resulted in an interesting strategy to obtain ergosterol- and Vitamin D-2-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 degrees 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 degrees C, 4 cm) to partially transform ergosterol into vitamin D-2. 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 D-4 formation although in lower amounts than vitamin D-2 or lumisterol(2) while with irradiation at 254 nm most of ergosterol was transformed into vitamin D-2.