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Abstract

An unknown vitamin D compound was observed in the HPLC-UV chromatogram of edible mushrooms in the course of analyzing vitamin D2 as part of a food composition study and confirmed by liquid chromatography-mass spectrometry to be vitamin D4 (22-dihydroergocalciferol). Vitamin D4 was quantified by HPLC with UV detection, with vitamin [3H] itamin D3 as an internal standard. White button, crimini, portabella, enoki, shiitake, maitake, oyster, morel, chanterelle, and UV-treated portabella mushrooms were analyzed, as four composites each of a total of 71 samples from U.S. retail suppliers and producers. Vitamin D4 was present (>0.1 µg/100 g) in a total of 18 composites and in at least one composite of each mushroom type except white button. The level was highest in samples with known UV exposure: vitamin D enhanced portabella, and maitake mushrooms from one supplier (0.2–7.0 and 22.5–35.4 µg/100 g, respectively). Other mushrooms had detectable vitamin D4 in some but not all samples. In one composite of oyster mushrooms the vitamin D4 content was more than twice that of D2 (6.29 vs. 2.59 µg/100 g). Vitamin D4 exceeded 2 µg/100 g in the morel and chanterelle mushroom samples that contained D4, but was undetectable in two morel samples. The vitamin D4 precursor 22,23-dihydroergosterol was found in all composites (4.49–16.5 mg/100 g). Vitamin D4 should be expected to occur in mushrooms exposed to UV light, such as commercially produced vitamin D enhanced products, wild grown mushrooms or other mushrooms receiving incidental exposure. Because vitamin D4 coeluted with D3 in the routine HPLC analysis of vitamin D2 and an alternate mobile phase was necessary for resolution, researchers analyzing vitamin D2 in mushrooms and using D3 as an internal standard should verify that the system will resolve vitamins D3 and D4.

Samples

Samples of white button, crimini, portabella, enoki, shiitake, maitake, oyster, morel, UV-treated portabella, and chanterelle mushrooms were the same as described in detail in the previous report on vitamin D2 and sterols and comprised a total 71 original samples analyzed as four composites of each type of mushroom (two for chanterelle).

Vitamin D4 content of mushrooms

summarizes the assayed concentration (fresh weight basis) of vitamin D4 and its precursor, 22,23-dihydroergosterol in ten types of mushrooms (white button, crimini, portabella, enoki, shiitake, maitake, oyster, morel, and UV-treated portabella, and chanterelle) sampled from retail outlets in the U.S. Overall, vitamin D4 was detected (>0.1 µg/100 g) in 18 of the total of 38 composites analyzed and was present at an average concentration of 5.2 µg/100 g. However there was wide variability between and within samples different types of mushrooms. There were 7 samples known to contain mushrooms that had been exposed to UV light during production: the Mushroom CC, the vitamin D enhanced portabella, and the two maitake composites from supplier G (). All of these samples contained vitamin D4, and in some the concentration was similar to or greater than that of vitamin D2 (previously reported in Phillips et al. ). The two maitake mushroom samples that were high in vitamin D2 (63.2 and 48.9 µg/100 g) were also high in vitamin D4 (35.4 and 22.5 µg/100 g, respectively). These mushrooms were presumed to have been exposed to UV light under the growing conditions reportedly used by this producer . Of the mushrooms not known to have received UV exposure, vitamin D4 occurred in at least one composite of each type except white button. In oyster mushrooms the composite highest in vitamin D2 (2.59 µg/100 g) had a vitamin D4 content more than two-fold higher (6.29 µg/100 g). Vitamin D4 exceeded 2 µg/100 g in the morel and chanterelle mushroom samples that contained D4 (all but two morel composites).