Vitamin D-4 in Mushrooms

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] vitamin 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.