Shiitake and Vitamin D

KOBAYASHI Tadashi, TAKEUCHI Atsuko, OKANO Toshio

doi:10.20632/vso.62.9_483

The nutritional evaluation of vitamin D_2 in Shiitake (Lentinus edodes) was investigated. Vitamin D_2 in Shiitake was identified by HPLC, UV spectrum and GC-MS. The content of vitamin D_2 in Shiitake was assayed by a HPLC method previously established for the determination of the vitamin in foods, feeds and pharmaceuticals. The assayed values of vitamin D_2 in two kinds of raw Shiitake cultured outdoors and in a vinylhouse were 390 IU/100g (100 IU/a piece) and 73 IU/100g (14 IU/a piece) , respectively. The assayed values of the vitamin in two kinds of dried Shiitake, (Koshin and Donko) were 969 IU/100g (56 IU/a piece) and 300 IU/100g (12 IU/a piece), respectively. These results showed that the content of vitamin D_2 in Shiitake was comparatively higher than that in other foods. The content of vitamin D_2 in Shiitake was correlated with the quanta of UV light in solar radiation at cultivation places. The assayed values of vitamin D_2 in Shiitake increased about 2.5 times when exposed to sun light for 3 hours. The vitamin D_2 content in parts of Shiitake, pileus, stipe and gills, were 870, 2,240 and 470 IU/100g, respectively. Pre-vitamin D_2, which was photochemically produced from ergosterol and thermally isomerised into vitamin D_2 during heating, was identified by HPLC and GC-MS in raw Shiitake. The weight ratio of pre-D_2 to vitamin D_2 in raw Shiitake was about 7:1, whereas that in dried Shiitake was about 1:10. These results suggested that vitamin D_2 (including pre-D_2) was photochemically produced from ergosterol by solar radiation during farming.

Shiitake and Vitamin D

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