Vitamin D accumulation in king oyster mushroom stimulated by UV radiation

Abstract

Vitamin D plays a critical role in regulating calcium and phosphorus homeostasis in the human body and deficiency of vitamin D can result in rickets, osteomalacia and other diseases such as cancers, diabetes and cardiovascular diseases. Currently, vitamin D deficiency or insufficiency is still common worldwide with an estimated total number of one billion people, and over 50% of the population in Asia. Edible mushrooms are a good source of various vitamins but have a low or negligible content of vitamin D. UV radiation has been found effective to stimulate the accumulation of vitamin D from the conversion of ergosterol in edible mushrooms. King oyster mushroom (Pleurotus eryngii) is one of the most popular and tasty edible mushrooms. However, the content and dynamic trend of vitamin D in king oyster mushroom during UV irradiation are still not well characterized. This study was focused on the accumulation of some important vitamin D species (e.g. D2 and D4) and their dynamic relationships in King oyster mushrooms during UV-B irradiation. Our first study was on the stimulation of vitamin D2 and vitamin D4 accumulation in the oyster mushrooms by UVB irradiation for various periods of time. The contents of vitamin D2 and D4 showed a linear increase with time (D2: y = 0.998x + 15.75, r² = 0.973; D4: y = 0.081x + 0.389, r² = 0.834), and provitamin D2 a linear decrease (y = 0.003x + 2.09, r2 = 0.942) within 30 minute of UVB irradiation. The relationship between vitamin D2 and provitamin D2 can be fitted to a parabolic model (y = 7127x² 29150x + 298311). Vitamin D2 and vitamin D4 showed a linear correlation (y=10.91x + 13.58, r²=0.935), indicating a synchronic increase during UVB radiation. Another major part of our study was to develop effective high performance liquid chromatographic (HPLC) methods for quantitative analysis of the vitamin D contents in the mushroom with simplified sample preparation. These HPLC methods showed high precision and repeatability and recovery for quantification of vitamin D2, provitamin D2 and vitamin D4. In summary, this study has developed effective HPLC methods for quantification of major vitamin D species in mushrooms, the dynamic trend of vitamin D2, provitamin D2 and vitamin D4 during UVB irradiation. These will provide useful references for enhancement of vitamin D accumulation in mushrooms by UV radiation and for quantitative analysis of the vitamin D contents.