Quantitation of total vitamin D2 and D4 in UV-exposed mushrooms using HPLC with UV detection after novel two-step solid phase extraction

A robust method for quantitation of total vitamin D2 and D4 in mushrooms by high performance liquid chromatography with UV detection (HPLC-UV) was developed to analyze mushrooms exposed to UV light. A two-step solid phase extraction (SPE) (silica, carbon black) removed chromatographic interferences typically resolved only with mass spectrometric detection (LC-MS) and allowed quantitation of all vitamin D and pre-D analytes. The vitamin and pre-vitamin forms of D2, D4 and D3 (internal standard), as well as other photoisomers and sterols were resolved. Results for six types of UV-exposed mushrooms were comparable to LC-MS. Screening of ten additional types of UV-exposed mushrooms without the IS confirmed lack of interference with the IS. The limit of quantification (µg/100 g fresh weight) was 0.4 for vitamin D and 0.9 for pre-vitamin D. Mushrooms do not have to be dried, and separatory funnels and large solvent volumes were also eliminated from sample preparation.

Triple quadrupole liquid chromatography-mass spectrometry-mediated evaluation of vitamin D2 accumulation potential, antioxidant capacities, and total polyphenol content of white jelly mushroom (Tremella fuciformis Berk.)

Tremella fuciformis Berk. (TF), or the white jelly mushroom, is well known for its myriad of pharmacological properties, such as immunomodulatory, anti-inflammatory, antidiabetic, antitumor, and antioxidant activities, and hypocholesterolemic and hepatoprotective effects that boost human health. Most of the studies of TF are concentrated on its polysaccharide (glucuronoxylomannan) composition, which is responsible for its pharmacological as well as rheological properties. It is well established that mushrooms are a great source of dietary vitamin D due to the presence of ergosterol in their cell membrane. There is a lack of published data on TF as a source of vitamin D2. Therefore, this study aimed to evaluate the vitamin D2 composition of the fruiting bodies of TF using triple quadrupole liquid chromatography-mass spectrometry (LC-MS/QQQ). The results showed highest vitamin D2 content (292.02 µg/g dry weight) in the sample irradiated with ultraviolet B (UVB; 310 nm) for 180 min as compared with the control group (52.47 µg/g dry weight) (P ≤ 0.001). The results showed higher accumulation potential of vitamin D2 in TF as compared with published data available for other extensively studied culinary mushrooms, such as Agaricus bisporus, Lentinula edodes, Pleurotus ostreatus, Cordiceps militaris, and Calocybe indica. Moreover, the impact of UV treatment on antioxidant capacities and total polyphenol content of TF was also studied. The accumulation potential of vitamin D in TF reveals a novel commercial source for this nutrient.

Discrimination of Milk from Different Animal Species by a Foodomics Approach Based on High-Resolution Mass Spectrometry

An untargeted foodomics strategy based on ultra-high-performance liquid chromatography coupled with quadrupole orbitrap and chemometrics was used to observe subtle differences in the molecule profiles of raw milk from different animal species (cow milk, goat milk, and water buffalo milk), which could prevent the fraud activities in the dairy industry. In data-dependent acquisition (DIA), spectra for all precursor ions facilitated the comprehensive identification of unknown compounds in untargeted foodomics. Chemometrics techniques were used to analyze large amounts of complex data to observe the separation of different sample groups and find the potential markers of sample groups. Finally, five markers were putatively identified by the potential marker identification workflow. The quantification results showed that β-carotene was found only in cow milk; ergocalciferol was found only in water buffalo milk; and the contents of nonanoic acid, decanoic acid, and octanoic acid were higher in goat milk than those in cow milk and water buffalo milk. The quantification of β-carotene enabled the detection of cow milk with a sensitivity threshold of 5% (w/w). This work provided an efficient approach for the discrimination of cow milk, goat milk, and water buffalo milk. Compared with proteomics and genomics, the simpler analytical procedures, lower costs, and higher speed of this work make it of great benefit for routine operations.

Single-Laboratory Validation of a Method for Determination of Ergocalciferol in Protein Drink Powders and Tablets by LC-MS/MS

Background: Currently, there is a lack of validation studies available in the literature for the determination of ergocalciferol, especially for those using a direct extraction technique. The current official methodologies for the quantification of ergocalciferol require saponification, liquid-liquid extraction, or both, thus requiring experienced technicians and specialized reflux equipment. This work provides a method that is more easily accessible to laboratories without these resources while still achieving the robustness needed for a successful validation of low levels of ergocalciferol in complex matrixes. Objective: A single-laboratory validation study was conducted for a rapid quantification method of ergocalciferol in protein drink powders and tablets. Methods: The method uses an LC-MS/MS with multimode source utilizing atmospheric pressure chemical ionization positive ionization mode. For both protein drink powders and tablets, the procedure consisted of a liquid extraction step using dimethyl sulfoxide and methanol. Isotopically labeled ergocalciferol was used as an internal standard to correct for signal depression caused by matrix interference. Results: This LC-MS/MS method was found to be accurate, precise, linear (from 0.01 to 0.3 μg/mL), rugged, and suitable for protein drink powders and tablets. Conclusions: The method was validated and is suitable for accurate quantification of ergocalciferol in tablet and protein powder products. Highlights: This work provides a validated method for accurate quantification of ergocalciferol in complex matrixes using a direct extraction technique. This may benefit quality control laboratories in the food and nutraceutical industries, where simple and efficient methodology is key to optimal functioning.

Evidence of vitamin D synthesis in insects exposed to UVb light

Vertebrates obtain the prohormone vitamin D primarily by endogenous cutaneous synthesis under ultraviolet b (UVb) exposure. To date, endogenous synthesis of vitamin D in insects has never been investigated. In an initial experiment, we exposed four insect species which differ in ecology and morphology (migratory locusts, house crickets, yellow mealworms and black soldier fly larvae (BSFL)) to a low irradiance UVb source. In a second experiment we exposed these species to a higher UV irradiance, and in a third we tested the effect of exposure duration on vitamin D concentrations in yellow mealworms. Low irradiance UVb tended to increase vitamin D3 levels in house crickets, vitamin D2 levels in BSFL and vitamin D2 and D3 in yellow mealworms. Higher UVb irradiance increased vitamin D3 levels in all species but BSFL. Both BSFL and migratory locusts had increased vitamin D2 levels. Longer UVb exposure of yellow mealworms increased vitamin D2 and increased vitamin D3 until a plateau was reached at 6400 IU/kg. This study shows that insects can synthesize vitamin D de novo and that the amounts depend on UVb irradiance and exposure duration.

The use of synthetic and natural vitamin D sources in pig diets to improve meat quality and vitamin D content

This study investigated the effects of synthetic and natural sources of vitamin D biofortification in pig diets on pork vitamin D activity and pork quality. One hundred and twenty pigs (60 male, 60 female) were assigned to one of four dietary treatments for a 55 d feeding period. The dietary treatments were (1)50 μg vitamin D₃/kg of feed; (2)50 μg of 25-hydroxvitamin D₃/kg of feed (25-OH-D₃); (3)50 μg vitamin D₂/kg of feed; (4)50 μg vitamin D₂-enriched mushrooms/kg of feed (Mushroom D₂). The pigs offered the 25-OH-D₃ diet exhibited the highest (P < 0.001) serum total 25-hydroxyvitamin D concentration and subsequently exhibited the highest (P < 0.05) Longissimus thoracis (LT) total vitamin D activity. Mushroom D₂ and 25-OH-D₃ supplementation increased pork antioxidant status. The vitamin D₂-enriched mushrooms improved (P < 0.05) pig performance, carcass weight and LT colour. In conclusion, 25-OH-D₃ is the most successful source for increasing pork vitamin D activity, while Mushroom D₂ may be a new avenue to improve animal performance and pork quality.

Analysis of Vitamin D₂ and Vitamin D₃ in Infant and Adult Nutritional Formulas by Liquid Chromatography-Tandem Mass Spectrometry: A Multilaboratory Testing Study

A multilaboratory testing study was conducted on AOAC First Action Method 2016.05 "Analysis of Vitamin D2 and Vitamin D3 in Fortified Milk Powders, Infant Formulas, and Adult/Pediatric Nutritional Formulas by Liquid Chromatography-Tandem Mass Spectrometry." Nine laboratories participated in the analysis of duplicate samples of 20 nutritional products. The samples were saponified at high temperature with lipid-soluble components extracted into isooctane; an aliquot was washed and vitamin D derivatized with 4-phenyl-1,2,4-triazoline-3,5-dione to form a high-molecular mass, easily ionizable adduct, extracted into acetonitrile and analyzed by reversed-phase LC-tandem MS. Stable isotope-labeled internal standards were used for quantitation to correct for losses in extraction and variation in derivatization and ionization efficiencies. Acceptable precision as RSD was demonstrated; repeatability ranged from 1.9 to 5.8% RSDr and reproducibility values ranged from 6.4 to 12.7% RSDR, with samples meeting the precision limits specified in the vitamin D Standard Method Performance Requirements and the guidelines recommended for the Horwitz ratio. Method accuracy was assessed using NIST 1849a Standard Reference Material, with a P-value of 0.32, indicating an absence of bias against the certified value. As expected, placebo samples not fortified with vitamin D returned negligible results.

Impact on Vitamin D2, Vitamin D4 and Agaritine in Agaricus bisporus Mushrooms after Artificial and Natural Solar UV Light Exposure

Commercial mushroom production can expose mushrooms post-harvest to UV light for purposes of vitamin D2 enrichment by converting the naturally occurring provitamin D2 (ergosterol). The objectives of the present study were to artificially simulate solar UV-B doses occurring naturally in Central Europe and to investigate vitamin D2 and vitamin D4 production in sliced Agaricus bisporus (button mushrooms) and to analyse and compare the agaritine content of naturally and artificially UV-irradiated mushrooms. Agaritine was measured for safety aspects even though there is no rationale for a link between UV light exposure and agaritine content. The artificial UV-B dose of 0.53 J/cm(2) raised the vitamin D2 content to significantly (P < 0.001) higher levels of 67.1 ± 9.9 μg/g dry weight (DW) than sun exposure (3.9 ± 0.8 μg/g dry DW). We observed a positive correlation between vitamin D4 and vitamin D2 production (r(2) = 0.96, P < 0.001) after artificial UV irradiation, with vitamin D4 levels ranging from 0 to 20.9 μg/g DW. The agaritine content varied widely but remained within normal ranges in all samples. Irrespective of the irradiation source, agaritine dropped dramatically in conjunction with all UV-B doses both artificial and natural solar, probably due to its known instability. The biological action of vitamin D from UV-exposed mushrooms reflects the activity of these two major vitamin D analogues (D2, D4). Vitamin D4 should be analysed and agaritine disregarded in future studies of UV-exposed mushrooms.

Analysis of Vitamin D2 and Vitamin D3 in Fortified Milk Powders and Infant and Nutritional Formulas by Liquid Chromatography-Tandem Mass Spectrometry: Single-Laboratory Validation, First Action 2016.05

A method for the determination of vitamin D2 and vitamin D3 in fortified milk powders and infant and adult nutritional formulas is described. Samples are saponified at high temperature and lipid-soluble components are extracted into isooctane. A portion of the isooctane layer is transferred and washed, and an aliquot of 4-phenyl-1,2,4-triazoline-3,5-dione is added to derivatize the vitamin D to form a high-molecular-mass, easily ionizable adduct. The vitamin D adduct is then re-extracted into a small volume of acetonitrile and analyzed by RPLC. Detection is by tandem MS, using multiple reaction monitoring. Stable isotope-labeled vitamin D2 and vitamin D3 internal standards are used for quantitation to correct for losses in extraction and any variation in derivatization and ionization efficiencies. A single-laboratory validation of the method using AOAC Stakeholder Panel on Infant Formula and Adult Nutritionals (SPIFAN) kit samples was performed and compared with parameters defined according to the vitamin D Standard Method Performance Requirements (SMPR(®)). Linearity was demonstrated over the range specified in the SMPR, with the LOD being estimated at below that required. Method spike recovery (vitamin D2, 97.0-99.2%; and vitamin D3, 96.0-101.0%) and RSDr (vitamin D3, 1.5-5.2%) were evaluated and compared favorably with limits in the vitamin D SMPR. Acceptable bias for vitamin D3 was demonstrated against both the certified value for National Institute of Standards and Technology 1849a Standard Reference material (P(α = 0.05) = 0.25) and AOAC INTERNATIONAL reference method 2002.05 (P(α = 0.05) = 0.09). The method was demonstrated to meet the requirements of the vitamin D SMPR as defined by SPIFAN, and was recently approved for Official First Action status by the AOAC Expert Review Panel on SPIFAN Nutrient Methods.

Dose-Response Effect of Sunlight on Vitamin D2 Production in Agaricus bisporus Mushrooms

The dose response effect of UV-B irradiation from sunlight on vitamin D2 content of sliced Agaricus bisporus (white button mushroom) during the process of sun-drying was investigated.Real-time UV-B and UV-A data were obtained using a high-performance spectroradiometer. During the first hour of sunlight exposure, the vitamin D2 content of the mushrooms increased in a linear manner, with concentrations increasing from 0.1 μg/g up to 3.9 ± 0.8 μg/g dry weight (DW). At the subsequent two measurements one and 3 h later, respectively, a plateau was reached. Two hours of additional exposure triggered a significant decline in vitamin D2 content. After just 15 min of sun exposure and an UV-B dose of 0.13 J/cm(2), the vitamin D2 content increased significantly to 2.2 ± 0.5 μg/g DW (P < 0.0001), which is equivalent to 17.6 μg (704 IU) vitamin D2 per 100 g of fresh mushrooms and comparable to levels found in fatty fish like the Atlantic salmon.

Consumption of vitamin D2 enhanced mushrooms is associated with improved bone health

Mushrooms are the best nonanimal food source of vitamin D2. Pulsed irradiation can enhance vitamin D2 in mushrooms quickly. We investigated the effect of supplementing high vitamin D2Pleurotus ferulae mushrooms in a mouse model of osteoporosis. Thirty-two female C57BL/6JNarl mice were divided into four groups including sham, ovariectomized (OVX), OVX+nonpulsed mushroom (NPM) and OVX+pulsed mushroom (PM). After 23 weeks of treatment, serum samples were analyzed for osteoblast and osteoclast indicators, as well as metabolites using NMR spectroscopy. To examine bone density, femurs were analyzed using micro-computed tomography. The NPM and PM treatment mice showed increased bone density in comparison with OVX mice. In addition, the PM mice showed higher osteoblast and lower osteoclast indicators in comparison with OVX mice. Serum metabolomics analysis indicated several metabolites that were different in PM mice, some of which could be correlated with bone health. Taken together, these results suggest that pulsed irradiated mushrooms are able to increase bone density in osteoporotic mice possibly through enhanced bone metabolism. Further studies in humans are needed to show their efficacy in preventing osteoporosis.

Mechanism of error caused by isotope-labeled internal standard: accurate method for simultaneous measurement of vitamin D and pre-vitamin D by liquid chromatography/tandem mass spectrometry

RATIONALE

Bias of up to 25% has been observed for vitamin D3 and D2 samples exposed to heating during sample preparation, even when isotope-labeled internal standards are used. The goals of this study were to identify the mechanism of the positive bias observed in measuring vitamin D3 and D2 by liquid chromatography/tandem mass spectrometry (LC/MS/MS) and determine a way to eliminate the error source.

METHODS

Several internal standards with varying locations of labeling were used for comparison in this study. Additionally, different temperatures (25, 37, 55, and 75 °C) and different treatment times were investigated for sample preparation and a LC/MS/MS method capable of simultaneously measuring vitamin D and pre-vitamin D was developed.

RESULTS

It was demonstrated that the different conversion behaviors of the analyte and the internal standard were the cause of the positive bias. This bias was eliminated when internal standards with labeling remote from the double-bond area of the molecules were used. Additionally, sample preparation was shortened from overnight saponification at room temperature to 0.5 h at 75 °C.

CONCLUSIONS

The use of an internal standard with labeling remote from the conjugated area eliminated the error source and gave accurate correction at all of the temperatures investigated. Heating may be used for rapid sample preparation as an alternative to overnight saponification at room temperature. This work not only describes the mechanism of an inaccurate internal standard correction, but also establishes a rapid LC/MS/MS method for simultaneous measurement of vitamin D and pre-vitamin D.

Simultaneous determination of vitamins D2 and D3 by electrospray ionization LC/MS/MS in infant formula and adult nutritionals: First Action 2012.11

A method was developed for the analysis of vitamins D2 and D3 in a variety of nutritional products. To extract vitamins D2 and D3 from products containing substantial amounts of fat, a saponification with alcoholic potassium hydroxide is required to release the vitamin D. Trideuterium-labeled vitamin D is added to the sample prior to saponification, and quantitation is achieved using linear regression of the ratio of peak response for 2H3-D and vitamin D. Acceptable linearity was achieved between 0.6 and 27 microg/100 g with a correlation requirement of >0.999. The method detection limit of 0.02 microg/100 g was verified by spiking placebo products carried through the saponification and extraction steps of the method. At the quantitation limit (0.12 microg/100 g), the signal was easily distinguished from the background. Vitamin D3 spike recoveries ranged from 107 to 119% at the low level and 104 to 116% at the high-level spike. Vitamin D2 recoveries were 105 to 116% and 91 to 110% for the low- and high-level spikes, respectively. SRM 1849a has a certified concentration of 11.1 +/- 1.7 microg/100 g; using this standard reference material, the range of 9.4 to 12.8 microg/100 g was met on each of the 6 days. Method repeatability, determined in 12 vitamin D3 product matrixes over 6 days, ranged from 3.9 to 48%. The adult nutrition-milk protein sample was the most notable; it failed within-day, as well as day-to-day, precision requirements. There was no attempt to optimize the sample preparation to accommodate any problem matrix.

Determination of vitamins D2 and D3 in infant formula and adult nutritionals by ultra-pressure liquid chromatography with tandem mass spectrometry detection (UPLC-MS/MS): First Action 2011.12

The method for the "Determination of Vitamins D2 and D3 in Infant Formula and Adult Nutritionals by Ultra-Pressure Liquid Chromatography with Tandem Mass Spectrometry Detection (UPLC-MS/MS)" was adopted as AOAC Official First Action during the "Standards Development and International Harmonization: AOAC INTERNATIONAL Mid-Year Meeting" held June 29, 2011. During the meeting, an Expert Review Panel (ERP) evaluated the available validation information against standard method performance requirements (SMPRs) articulated by stakeholders. The method, approved by the ERP, is applicable for the determination of vitamin D (total vitamins D2 and D3). A range of products had been tested during a single-laboratory validation study. The products included butter, National Institute of Standards and Technology SRM 1849, eggs, cheese, yogurt, ready-to-eat cereal, bread, mushrooms, and tuna. The testing of the method established linearity in the range of 0.005-50 microg/mL. The recovery range was 93.4-100.9% for vitamin D2 and 102.4-106.2% for vitamin D3. The LOD and LOQ for vitamin D2 were reported as 0.20 and 0.61 microgl100 g, respectively; for vitamin D3, the reported values were 0.47 and 1.44 microg/100 g, respectively. The method met the SMPRs set by the Stakeholder Panel on Infant Formula and Adult Nutritionals (SPIFAN). It was, therefore, decided that the method was appropriate for Official First Action Method status.

Impact of high-pressure processing on vitamin E (α-, γ-, and δ-tocopherol), vitamin D (cholecalciferol and ergocalciferol), and fatty acid profiles in liquid foods

In the present study, four high-pressure (HP) treatments (100, 200, 300, and 400 MPa) of 9 min duration were evaluated to assess their effect on the lipid fraction (fat-soluble vitamins and fatty acid profile) of an orange juice-milk and a vegetable beverage. After HP treatment, nonsignificant changes in vitamin D(2) and D(3) contents were observed for both beverages. An increase in vitamin E activity was observed in HP beverages when pressures >100 MPa were applied, mainly due to an increase in α-tocopherol content. Only a small reduction in fat content was found for the orange juice-milk beverage, but no changes were observed for the vegetable beverage. A significant decrease in SFA levels was observed in HP-treated (300-400 MPa) orange juice-milk. With regard to MUFA, a significant increase in oleic acid (C(18:1)) was found in both liquid foods. Nonsignificant differences in the PUFA profiles were observed after HP processing.

Effects of postharvest pulsed UV light treatment of white button mushrooms (Agaricus bisporus) on vitamin D2 content and quality attributes

Pulsed UV light (PUV) was investigated as a means to rapidly increase vitamin D(2) (D(2)) content in fresh button mushrooms (Agaricus bisporus). D(2) was found to increase to over 100% RDA/serving following 3 pulses (1 s). Following 12 pulses, D(2) began to approach a maximum concentration of 27 μg/g DW. The D(2) produced with 3 pulses decreased from 11.9 to 9.05 μg/g DW after 3 days of storage; however, D(2) levels remained nearly constant after this point throughout an 11-day shelf life study. PUV treated sliced mushrooms produced significantly more D(2) than whole mushrooms, and it was also observed that brown buttons generated significantly less D(2) than white buttons. Several quality attributes were assessed, and no significant differences between control and PUV treated mushrooms were observed. These findings suggest that PUV treatment is a viable method for rapidly increasing the D(2) content of fresh mushrooms without adversely affecting quality parameters.

Seasonal variation of provitamin D2 and vitamin D2 in perennial ryegrass (Lolium perenne L.)

Ergosterol (provitamin D(2)) is converted to vitamin D(2) in grass by exposure to UV light. Six varieties of perennial ryegrass (Lolium perenne L.) were harvested four times during the season, and the contents of vitamin D(2) and ergosterol were analyzed by a sensitive and selective liquid chromatography tandem mass spectrometry method. Weather factors were recorded, and a principal component analysis was performed to study which factors were important for the formation of vitamin D(2). The results suggest that a combination of weather factors is involved and that the contents of ergosterol and vitamin D(2) change more than a factor of 10 during the season. These results demonstrate that grass potentially can be a significant source of vitamin D for grazing animals and animals fed on silage and hay.

Vitamin D and sterol composition of 10 types of mushrooms from retail suppliers in the United States

Vitamin D(2) (ergocalciferol) and sterols were analyzed in mushrooms sampled nationwide in the United States to update the USDA Nutrient Database for Standard Reference. Vitamin D(2) was assayed using HPLC with [(3)H]-vitamin D(3) internal standard and sterols by GC-FID mass spectrometric (MS) confirmation. Vitamin D(2) was low (0.1-0.3 μg/100 g) in Agaricus bisporus (white button, crimini, portabella) and enoki, moderate in shiitake and oyster (0.4-0.7 μg/100 g), and high in morel, chanterelle, maitake (5.2-28.1 μg/100 g) and UV-treated portabella (3.4-20.9 μg/100 g), with significant variability among composites for some types. Ergosterol (mg/100 g) was highest in maitake and shiitake (79.2, 84.9) and lowest in morel and enoki (26.3, 35.5); the range was <10 mg/100 g among white button composites but 12-50 mg/100 g among samples of other types. All mushrooms contained ergosta-5,7-dienol (22,23-dihydroergosterol) (3.53-18.0 mg/100 g) and (except morel) ergosta-7-enol. Only morel contained brassicasterol (28.6 mg/100 g) and campesterol (1.23-4.54 mg/100 g) and no ergosta-7,22-dienol. MS was critical in distinguishing campesterol from ergosta-7,22-dienol.

Application of ultra-performance liquid chromatography/tandem mass spectrometry for the measurement of vitamin D in foods and nutritional supplements

Ultra-performance liquid chromatography (UPLC)/MS/MS was applied to measure vitamin D in various foods and nutritional supplements. The run-time of the chromatographic separation was cut from 20 min in HPLC/MS/MS to 10 min in UPLC/MS/MS, while equal or better separation efficiency was achieved to deal with complex food matrixes. Under the optimized conditions, all the previtamins of vitamin D3, D2, and isotope-labeled vitamin D3 were baseline-separated from their corresponding vitamins. It was also demonstrated that many sterol isomers in complex food matrixes that interfere in the analysis could be well-separated from the analytes. Accuracy of this method was evaluated by analysis of NIST SRM 1849 infant formula reference material. With eight replicates, the average vitamin D3 concentration was 0.251 +/- 0.012 mg/kg, an excellent agreement with the certified value of 0.251 +/- 0.027 mg/kg. In addition, spike recovery from a commercial infant formula matrix was in the range of 100 to 108% for both vitamins D3 and D2 at three spike concentration levels. The spike recovery for an even more complex matrix, pet food, was 101-105%. LOQ values were 0.026 and 0.033 IU/g, or 0.086 and 0.11 IU/mL in solution, for vitamins D3 and D2, respectively. The dynamic range had three orders of magnitude, which made the method flexible and useful to deal with the wide concentration range of vitamin D in various samples. The method was robust based on the results of changing the parameters of LC separation and MS measurement. This accurate and reliable vitamin D method increased instrument efficiency and analysis productivity significantly.

Measurement of vitamin D in foods and nutritional supplements by liquid chromatography/tandem mass spectrometry

Vitamin D is a fat-soluble vitamin with great nutritional interest. An HPLC/MS/MS method was developed to measure vitamin D with atmospheric pressure chemical ionization. Under the experimental parameters used, the LOQ was 0.018 IU/g or 0.45 ng/g, which greatly enhances the capability of measurement of vitamin D at low levels in foods and supplements. This method was validated with spike recovery of 100 +/- 15% and the RSD of less than 10% for most sample matrixes, including infant formula, cheese, cereal and cereal-based foods, multivitamin supplements, and pet foods. The results for vitamin D were compared with those obtained by other methods.

Vitamin D2 formation and bioavailability from Agaricus bisporus button mushrooms treated with ultraviolet irradiation

Agaricus bisporus mushrooms contain an abundance of ergosterol, which on exposure to UV irradiation is converted to vitamin D2. The present study evaluated the effects UV-C irradiation on vitamin D2 formation and its bioavailability in rats. Fresh button mushrooms were exposed to UV-C irradiation at mean intensities of 0.403, 0.316, and 0.256 mW/cm(2) from respective distances of 30, 40, and 50 cm for periods ranging from 2.5 to 60 min. Vitamin D2 and ergosterol were measured by HPLC-MS/MS. The stability and retention of vitamin D2 were assessed including the extent of discoloration during storage at 4 degrees C or at room temperature. Exposure to UV-C irradiation at 0.403 mW/cm(2) intensity from 30 cm distance resulted in a time-dependent increase in vitamin D2 concentrations that was significantly higher than those produced at intensities of 0.316 and 0.256 mW/cm(2) from distances of 40 and 50 cm, respectively. Furthermore, the concentrations of vitamin D2 produced after exposure to UV-C irradiation doses of 0.125 and 0.25 J/cm(2) for, 2.5, 5, and 10 min were 6.6, 15.6, and 23.1 microg/g solids, equivalent to 40.6, 95.4, and 141 microg/serving, respectively. The data showed a high rate of conversion from ergosterol to vitamin D2 at short treatment time, which is required by the mushroom industry. The stability of vitamin D2 remained unchanged during storage at 4 degrees C and at room temperature over 8 days (P = 0.36), indicating no degradation of vitamin D2. By visual assessment or using a chromometer, no significant discoloration of irradiated mushrooms, as measured by the degree of "whiteness", was observed when stored at 4 degrees C compared to that observed with mushrooms stored at room temperature over an 8 day period (P < 0.007). Vitamin D2 was well absorbed and metabolized as evidenced by the serum response of 25-hydroxyvitamin D in rats fed the irradiated mushrooms. Taken together, the data suggest that commercial production of button mushrooms enriched with vitamin D2 for improving consumer health may be practical.

Simultaneous determination of cholecalciferol (vitamin D3) and ergocalciferol (vitamin D2) in foods by selected reaction monitoring

Cholecalciferol (vitamin D3) and ergocalciferol (vitamin D2) were determined simultaneously by selected reaction monitoring (SRM) mass spectrometry for different food matrixes. A small amount of starting sample was saponified and extracted before injection into a linear ion trap mass spectrometer equipped with an atmospheric pressure chemical ionization source. Dihydrotachysterol, which is absent from food and has a structure similar to that of vitamins D3 and D2, was used as an internal standard. Calibration curves for the 2 vitamins showed linearity with R2 values of 0.9999 and 0.9989 for vitamins D3 and D2, respectively. Limits of detection for vitamins D3 and D2 were 0.5 ng/g (1.3 pmol/g) and 1.75 ng/g (4.4 pmol/g) and limits of quantitation were 1.25 ng/g (3.24 pmol/g), and 3.75 ng/g (9.45 pmol/g), respectively. Accuracy and precision of the method were tested with the infant formula reference standard of the National Institute of Standards and Technology, which showed a relative standard deviation of 6%. Recoveries ranged from 95 to 105%. Several food products were tested with AOAC Method 982.29, which is currently in use for vitamins D3 and D2, and results were comparable within 6%.

Effect of UV-B exposure on the concentration of vitamin D2 in sliced shiitake mushroom (Lentinus edodes) and white button mushroom (Agaricus bisporus)

The aim of this study was to investigate the effect of UV-B on vitamin D 2 concentration in shiitake mushrooms and in white button mushrooms. After the exposure to UV-B, at a dose of 25 kJ/m(2), the concentration of vitamin D(2) was increased to 36.7 +/- 1.4, 68.6 +/- 4.9, and 106.4 +/- 14.7 microg/g (dry weight) for pileus, middle, and gill parts of shiitake mushroom, respectively. The gill side of whole shiitake mushrooms exposed to 0, 25, 50, and 75 kJ/m(2) increased to 2.8 +/- 0.2, 13.8 +/- 1.9, 40.7 +/- 4.4, and 61.9 +/- 10.6 microg/g (dry weight) at 25 degrees C, respectively. Irradiating slices of white button mushroom was a more efficient way of increasing the vitamin D(2) content than irradiating the gill or pileus of whole mushrooms, due to the larger exposure area. As the irradiation doses increased, the vitamin D(2) concentration also increased for both types of mushrooms. In conclusion, exposure to ultraviolet light offers an effective way of increasing the concentration of vitamin D(2) in mushrooms.

Detection and quantification of provitamin D2 and vitamin D2 in hop (Humulus lupulus L.) by liquid chromatography-diode array detection-electrospray ionization tandem mass spectrometry

In this work, ergosterol and ergocalciferol were identified for the first time in hop. In addition, in this article, a simple and reliable analytical methodology for analysis of these compounds in different commercial forms of hop is presented. The performance of the method was assessed by the evaluation of parameters such as absolute recovery (higher than 70%), repeatability (lower than 3 %), linearity ( r(2) > 0.9988) and limits of detection (ranging from 0.034 for ergocalciferol to 0.058 mg/L for ergosterol) and quantification (ranging from 0.113 for ergocalciferol to 0.195 mg/L for ergosterol). On the basis of standard additions applied with the optimized procedure and high-performance liquid chromatography with diode array detection, it appears that the Nugget hop plant (crop 2006) contains 1.84 +/- 0.09 microg/g of ergosterol and 1.95 +/- 0.05 microg/g of ergocalciferol. The identity of the compounds was confirmed by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry in the positive ion mode. The presence of ergosterol here reported should have great potential for the assessment of hop as related to the fungal contamination proportion and hence the quality of this raw material.

Convenient analysis of vitamin D in cheese and other food matrixes by liquid chromatography/mass spectrometry

A convenient method is presented for determination of vitamin D in natural cheese, processed cheese, milk, cereals, noncarbonated soft drinks, and juice by liquid chromatography/ mass spectrometry (LC/MS). Samples were saponified, extracted, evaporated, redissolved in acetonitrile, and injected into an LC-atmospheric pressure chemical ionization-MS system with no preparative chromatographic steps. Vitamin D was determined by selected ion monitoring. MS response was linear for vitamin D3 and its internal standard vitamin D2, and overall average recoveries ranged from 98 to 105%. A blending experiment in which shredded vitamin D3-fortified cheddar was mixed with control nonfortified cheddar showed linearity. The limit of detection for vitamin D was 1.3 ng and the limit of quantitation was 3 ng. The method gave good accuracy and precision, with a standard deviation of 9.5 and relative standard deviation of 6.7%. Results for vitamin D3 obtained with this method for different food matrixes, at different levels, were in agreement with those obtained with the reference LC/UV method currently used by many laboratories and derived from AOAC Official Method 982.29.

[Determination of vitamins D2, vitamin D3 in cosmetics by high performance liquid chromatography]

OBJECTIVE

A high performance liquid chromatography method was used to detect vitamins D2 and vitamin D3, which is useful to know the use of vitamins D2 and vitamin D3 in cosmetics, prohibit the influx of cosmetics containing vitamins D2 and vitamin D3 to cosmetic market, safeguard the health of consumers.

METHODS

A high performance liquid chromatography method was established for determination of vitamins D2 and vitamin D3 in cosmetics. The separation condition was optimized by trying different type of columns and mobile phases.

RESULTS

The experiment goes on a Alltima C18 column (250 mm x 4.6 mm I. D., 5 microm)using methanol-acetonitrile (90: 10) as mobile phase at a flow rate of 1.0 ml/min, with the column temperature 25 degrees C and detection wave 265nm. The liner range is from 0.5 mg/L to 100 mg/L with good relationship. The detection limit of vitamin D2 is 0. 12 mg/L, the precision is less than 3.8% and recovery varies from 94.2% to 101.4%, while the detection limit of vitamin D3 is 0.06 mg/L, the precision is less than 3.5% and recovery varies from 91.6% to 97.2%.

CONCLUSION

The method is simple, precise and accurate, which is suitable for the determination of vitamins D2 and vitamin D3 in cosmetics.

Accelerated Mammary Gland Development during Pregnancy and Delayed Postlactational Involution in Vitamin D3 Receptor Null Mice

The vitamin D receptor (VDR) is present in mammary gland, and VDR ablation is associated with accelerated glandular development during puberty. VDR is a nuclear receptor whose ligand, 1,25-dihydroxyvitamin D [1,25-(OH)2D] is generated after metabolic activation of vitamin D by specific vitamin D hydroxylases. In these studies, we demonstrate that both the VDR and the vitamin D 1-α hydroxylase (CYP27B1), which produces 1,25-(OH)2D are present in mammary gland and dynamically regulated during pregnancy, lactation, and involution. Furthermore, we show that mice lacking VDR exhibit accelerated lobuloalveolar development and premature casein expression during pregnancy and delayed postlactational involution compared with mice with functional VDR. The delay in mammary gland regression after weaning of VDR knockout mice is associated with impaired apoptosis as demonstrated by reductions in terminal deoxynucleotidyl transferase-mediated deoxyuridine nick-end labeling staining, caspase-3 activation and Bax induction. Under the conditions used in this study, VDR ablation was not associated with hypocalcemia, suggesting that altered mammary gland development in the absence of the VDR is not related to disturbances in calcium homeostasis. Furthermore, in the setting of normocalcemia, VDR ablation does not affect milk protein or calcium content. These studies suggest that the VDR contributes to mammary cell turnover during the reproductive cycle, and its effects may be mediated via both endocrine and autocrine signaling pathways. Unlike many mammary regulatory factors that exert transient, stage-specific effects, VDR signaling impacts on mammary gland biology during all phases of the reproductive cycle.

Effect of vitamin D2- and D3-enriched diets on egg vitamin D content, production, and bird condition during an entire production period

Vitamin D insufficiency during winter is a common problem for humans in Europe. One way to ease this problem is through the production of vitamin D-fortified eggs. To evaluate such a production process, the effects of vitamin D supplementation during an entire production period were assessed. Transfer of vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol) from the diet to egg yolks was measured using 2 different levels of both vitamins (6,000 and 15,000 IU/kg feed) relative to a control treatment (2,500 IU vitamin D3/kg feed). During the experiment, production parameters, egg quality (egg weight, Haugh unit, specific gravity, eggshell fracture force, and Ca content of eggshell), and the condition of hens were monitored. At the end of the experiment histopathological tests were performed. Supplementing diets with vitamin D3 increased egg yolk vitamin D content more effectively than did supplementation with vitamin D2. For groups of hens receiving 6,000 or 15,000 IU of vitamin D3/kg feed, egg yolk vitamin D3 content ranged from 9.1 to 13.6 and from 25.3 to 33.7 microg/100 g, respectively. Corresponding values for birds fed vitamin D2 were 4.7 to 7.0 and 13.3 to 21.0 microg/100 g. Both supplements enhanced vitamin D3 content of egg yolks relative to the control diet (2.5 to 5.0 microg/100 g of egg yolk). Vitamin D supplements had no effects on production parameters compared with the control diet. However, especially vitamin D3 improved bone strength (P < 0.05). Autopsy at the end of the experiment indicated no detrimental accumulation of calcium in the kidneys, liver, heart, muscles, or lungs.

[Ergocalciferol Reference Standard (Control 031) of National Institute of Health Sciences]

The raw material of ergocalciferol was examined for the preparation of the "Ergocalsiferol Reference Standard (Control 031)", The analytical data obtained were: melting point, 114.5 degrees C; UV spectrum, lambda max of 264.8 nm and specific absorbance in ethanol at 265 nm = 474.7; IR spectrum, same as that of the Ergocalciferol Reference Standard (Control 003); optical rotation, [alpha]20(D) = +104.6 degrees ; thin-layer chromatography, two impurities were detected at 50 micrograms; high-performance liquid chromatography, total amount of impurities estimated to be less than 0.04%. Based on the above results, the raw material was authorized as the Japanese Pharmacopoeia Ergocalciferol Reference Standard (Control 031) of the National Institute of Health Sciences.

[Ergocalciferol Reference Standard (Control 001) of National Institute of Health Sciences]

The raw material of ergocalciferol was examined for the preparation of "Ergocalciferol Reference Standard (Control 001)". Analytical data obtained were: melting point, 114.8 degrees C; UV and infrared spectra, the same as those of JP Ergocalciferol Reference Standard (Control 971); specific absorbance, E1ca1% = 471(265 nm); optical rotation, [alpha]D20 = +102.4 degrees; thin-layer chromatography, no impurities were detected until 100 micrograms; high-performance liquid chromatography (HPLC), total amount of impurities estimated to be less than 0.1%. Based on the above results, the raw material was authorized as the Japanese Pharmacopoeia Ergocalciferol Reference Standard (Control 001).

In Vitro Metabolism of 19-Nor-1α,25-(OH)2D2 in Cultured Cell Lines: Inducible Synthesis of Lipid- and Water-Soluble Metabolites

The active vitamin D analog, 19-nor-1alpha,25-dihydroxyvitamin D2 (19-nor-1alpha,25-(OH)2D2), has a similar structure to the natural vitamin D hormone, 1a,25-dihydroxyvitamin D3 (1alpha,25-(OH)2D3), but lacks the C10-19 methylene group and possesses an ergosterol/ vitamin D2 rather than a cholesterol/vitamin D3 side chain. We have used this analog to investigate whether any of these structural features has any effect upon the type and rate of in vitro metabolism observed. Using a vitamin D-target cell, the human keratinocyte, HPK1A-ras, we observed formation of a number of metabolites, three of which were purified by extensive HPLC and conclusively identified by a combination of GC-MS and chemical derivatization as 19-nor-1alpha,24,25-(OH) 3D2, 19-nor-1alpha,24,25,26-(OH) 4D2, and 19-nor-1alpha,24,25,28-(OH)4,D2. The first metabolite is probably a product of the vitamin D-inducible cytochrome P450, P450cc24 (CYP24), while the latter two metabolites are likely to be further metabolic products of 19-nor-1alpha,24,25-(OH)3D2. These hydroxylated metabolites resemble those identified by other workers as products of the metabolism of 1alpha,25-(OH)2D2 in the perfused rat kidney. It therefore appears from the similar metabolic fate of 19-nor-1alpha,25-(OH)2D2 and 1alpha,25-(OH)2D2 that the lack of the C10-19 methylene group has little effect upon the nature of the lipid-soluble metabolic products and the rate of formation of these products seems to be comparable to that of products of 1alpha,25-(OH)2D3 in vitamin D-target cells. We also found extensive metabolism of 19-nor-1alpha,25(OH)2D2 to water-soluble metabolites in HPK1A-ras, metabolites which remain unidentified at this time. When we incubated 19-nor-1alpha,25-(OH)2D2 with the liver cell line HepG2, we obtained only 19-nor-1alpha,24,25-(OH)3D2. We conclude that 19-nor-1alpha,25-(OH)2D2 is efficiently metabolized by both vitamin D-target cells and liver cells.

Determination of vitamin D2 in emulsified nutritional supplements by solid-phase extraction and column-switching high-performance liquid chromatography with UV detection

This paper deals with a method for solid-phase extraction of trace amounts of vitamin D2 (VD2, 19 ng/g) from emulsified nutritional supplements, which contain 50 kinds of compounds, followed by column-switching high-performance liquid chromatography (HPLC) with UV detection at 265 nm. VD2 is present at 1000-20,000,000 times lower concentration than other components. Bond Elut C18 cartridge was chosen as for the emulsified nutritional supplements after comparison with eight other types. A sample solution was applied to the solid-phase extraction cartridge and VD2 was eluted by methanol followed by HPLC. The effects of sample pH, eluent composition and eluate volume on the retention and elution of VD2 on Bond Elut C18 cartridge were examined. The resulting method was simple, rapid (analysis time: approximately 20 min), sensitive (detection limit: approximately 0.1 ng per injection (200 microl) at a signal-to-noise ratio 3:1), and reproducible (relative standard deviation: approximately 6.2%, n=5). The calibration graph for VD2 was linear in the range of 0.1-3 ng per injection (200 microl). Recovery of VD2 was approximately 80% by the standard addition method.

[Determination of vitamin D2 included with beta-cyclodextrin complex in "longmu zhuanggu chongji" by HPLC]

In order to enhance the stability of vitamin D2(VD2), the inclusion complex of VD2 with beta-cyclodextrin(beta-CD) was added in "Longmu Zhuanggu Chongji", a medicine of children for the prevention and cure of rickets. The VD2 in beta-CD-VD2 inclusion complex was satisfactorily determined by both reversed-phase high performance liquid chromatography(HPLC) and ultraviolet spectrometry(UV). The experimental results from UV were in well consistent with those from HPLC. The accuracy and recovery of HPLC measurement were analyzed, and their relative standard deviation(RSD) were given to be 0.63% and 1.54%, indicating the method is quite correct and reliable, and the linear regression equation is reasonable. The "Longmu Zhuanggu Chongji" containing beta-CD-VD2 inclusion complexes was saponified by a mixture of KOH, vitamin C (VC) and alcohol-water(1:2, V/V) at 70 degrees C, then extracted with petroleum ether. An accurate content of the VD2 product was obtained by HPLC. A simple and rapid HPLC method, which can detect VD2 in the inclusion complex and in "Longmu Zhuanggu Chongji", has been established in this work.

Coupling of capillary electrochromatography to coordination ion spray mass spectrometry, a novel detection method

Miniaturized separation techniques such as capillary electrochromatography (CEC), pressurized capillary electrochromatography (pCEC) and capillary high performance liquid chromatography (CHPLC) have been coupled to a new detection technique: coordination ion spray mass spectrometry (CIS-MS). Electrospray ionization (ESI) has found widespread applications in mass spectrometry (MS) for the analysis of polar compounds such as peptides or nucleotides. However, for weakly polar or nonpolar substances, ESI-MS yields poor sensitivity since, in the absence of basic or acidic groups, protonation or deprotonation is not possible. CIS is a universal ionization technique capable of detecting these compounds. Through the addition of a central complexing ion, charged coordination compounds are formed, enabling the detection with good sensitivity. Using the coaxial sheath flow interface commonly employed in CE-MS coupling, we were able to separate and detect various important natural compounds such as unsaturated fatty acid methyl esters, vitamins D2 and D3, and four different estrogens. A central ion solution of 100 microg/mL AgNO3 in water was used as sheath flow liquid, resulting in the formation of positively charged coordination compounds.

[Ergocalciferol Reference Standard (Control 971) of National Institute of Health Sciences]

The raw material for ergocalciferol was examined for preparation of the "Ergocalciferol Reference Standard (Control 971)". Analytical data obtained were as follows: melting point, 116.7 degrees C; UV and infrared spectra, the same as those for JP Cholecalciferol Reference Standard; specific absorbance, E1 cm 1% = 461(265 nm); optical rotation, [alpha]D20 = +102.5 degrees; thin-layer chromatography and high-performance liquid chromatography (HPLC), no impurity was detected; assay, 102.4% by HPLC. Based on the above results, the raw material was authorized as the Ergocalciferol Reference Standard (Control 971) of National Institute of Health Sciences.

Characterization of monoglucuronides of vitamin D2 and 25-hydroxyvitamin D2 in rat bile using high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

The characterization of vitamin D2 3-glucuronide, 25-hydroxyvitamin D2 3-glucuronide and 25-hydroxyvitamin D2 25-glucuronide, biliary metabolites obtained from rats dosed with vitamin D2 and 25-hydroxyvitamin D2 per os, was carried out using HPLC-atmospheric pressure chemical ionization (APCI)-MS. The glucuronide obtained from bile specimens was identified by comparison of its chromatographic behaviour with an authentic sample using HPLC-APCI-MS operating in the negative-ion mode. Methylation of the respective fraction with diazomethane gave the methyl ester, which was also confirmed by HPLC-APCI-MS operating in the positive-ion mode. The (M-H)- and (M + NH4)+ ions were monitored in the selected-ion monitoring mode.

Hypervitaminosis D associated with drinking milk

BACKGROUND

Vitamin D has been added to milk in the United States since the 1930s to prevent rickets. We report the unusual occurrence of eight cases of vitamin D intoxication that appear to have been caused by excessive vitamin D fortification of dairy milk.

METHODS

Medical records were reviewed and a dietary questionnaire was sent to eight patients who had unexplained hypervitaminosis D. Vitamin D analyses with high-performance liquid chromatography were performed on samples of the patients' serum, the dairy milk they drank, and the vitamin D concentrate added to the milk.

RESULTS

All eight patients drank milk produced by a local dairy in amounts ranging from 1/2 to 3 cups (118 to 710 ml) daily. All had elevated serum 25-hydroxyvitamin D concentrations (mean [+/- SD], 731 +/- 434 nmol per liter [293 +/- 174 ng per milliliter]). Six of the eight patients had elevated serum vitamin D3 concentrations. Of the eight patients, seven had hypercalcemia and one had hypercalciuria but normocalcemia (mean serum calcium, 3.14 +/- 0.51 mmol per liter [12.6 +/- 2.1 mg per deciliter]). Analysis of the dairy's vitamin D-fortified milk revealed concentrations of vitamin D3 (cholecalciferol) that ranged from undetectable to as high as 232,565 IU per quart (245,840 IU per liter). An analysis of the concentrate that was used to fortify the milk, labeled as containing vitamin D2 (ergocalciferol), revealed that it contained vitamin D3.

CONCLUSIONS

Hypervitaminosis D may result from drinking milk that is incorrectly and excessively fortified with vitamin D. Milk that is fortified with vitamin D must be carefully monitored.

The vitamin D content of fortified milk and infant formula

BACKGROUND

The fortification of milk and infant formula with vitamin D has had an important role in eliminating rickets in children and osteomalacia in adults. A recent outbreak of vitamin D intoxication caused by drinking milk fortified with excess vitamin D has led to questions about the level of vitamin D in milk from other producers.

METHODS

We used high-performance liquid chromatography to measure vitamin D in samples of 13 brands of milk with various fat contents and 5 brands of infant formula purchased at random from local supermarkets in five Eastern states.

RESULTS

Only 12 (29 percent) of the 42 samples of the 13 brands of milk and none of the 10 samples of the 5 brands of infant formula contained 80 to 120 percent of the amount of vitamin D stated on the label. Twenty-six of the 42 milk samples (62 percent) contained less than 80 percent of the amount claimed on the label. No vitamin D was detected in 3 of the 14 samples of skim milk tested (lower limit of assay, 4.7 IU per quart [5.0 IU per liter]). One milk sample labeled as containing vitamin D2 (ergocalciferol) contained vitamin D3 (cholecalciferol). Seven of the 10 samples of infant formula contained more than 200 percent of the amount stated on the label; the sample with the highest concentration contained 419 percent of the stated amount. None of the samples of infant formula contained less than the amount stated.

CONCLUSIONS

Milk and infant-formula preparations rarely contain the amount of vitamin D stated on the label and may be either underfortified or overfortified. Since both underfortification and overfortification are hazardous, better monitoring of the fortification process is needed.

Microdetermination of vitamin D2 (ergocalciferol) using N-bromosuccinimide

A novel method for the microdetermination of vitamin D2 in its pure state and pharmaceutical preparations using N-bromosuccinimide (NBS) is reported. The new method is easy, simple, and accurate.

Analysis of vitamin D and its metabolites using thermospray liquid chromatography/mass spectrometry

A new method is described for the analysis of vitamin D and its metabolites utilizing thermospray (TSP) mass spectrometry as an on-line detector for high performance liquid chromatography. Ionization conditions were optimized for use with isocratic reversed phase chromatography. TSP mass spectrometry was employed in series with a UV absorbance detector to facilitate comparisons between the two methods of detection. Positive ion TSP mass spectra were recorded for vitamin D2, vitamin D3, 25-hydroxyvitamin D3 (25(OH)D3), 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) and 24,25-dihydroxyvitamin D3 (24,25(OH)2D3). The spectra contained protonated molecular ions, ammonium adduct ions and fragment ions due to the loss of one or more molecules of water. A comparison of quantitative precision was made by determining UV absorbance and TSP standard curves for vitamin D3 using two different methods: (1) External standard method with post-column (post UV detector) addition of ammonium acetate. (2) As (1) but using the method of internal standards with a closely eluting internal standard (vitamin D2). In each case the quantitative precision (correlation coefficient) for UV absorbance detection was superior owing to intrinsic instability of the TSP ion beam. A stable isotopically labelled internal standard was employed in the development of an assay for 1,25(OH)2D3. The assay was used to quantify in vitro enzymic conversion of 25(OH)D3 to 1,25(OH)2D3 in guinea pig and sheep renal mitochondrial incubations. TSP LC/MS was also applied to analysis of an extract of human blood plasma in which D3 and each of its principal metabolites were identified in a single analysis.

Liquid chromatographic determination of vitamin D in infant formula

A method is described for the determination of vitamins D2 + D3 in milk- and soy-based infant formula. Vitamins D2 and D3 are extracted from the saponified sample and converted to isotachysterols with acidified butanol. Reverse-phase liquid chromatography (LC) is used to remove interferences, and total vitamin D is quantitated using normal-phase LC. Recoveries of spiked samples averaged 97.6% for milk-based infant formula, and 98.8% for soy-based infant formula. This method quantitates vitamin D2 + D3 in infant formulas containing as low as 40 IU/qt when prepared according to label direction.

Metabolism of vitamin D2 in pig liver homogenates: evidence for a free radical reaction

In vitro hydroxylation of vitamin D2 at carbon-24 (C-24) was demonstrated with pig liver homogenate. The putative 24-hydroxyvitamin D2 (24-OHD2) comigrated with standard 24-OHD2 on a Zorbax Sil column developed in hexane/isopropanol (98/2). Rechromatography in methylene chloride/methanol (99.8/0.2) resolved the putative 24-OHD2 into two components. The identity of these compounds was determined to be 24(R)-OHD2 and 24(S)-OHD2 (epimers) by low resolution mass spectroscopy and proton NMR spectroscopy. The fact that epimers of 24-OHD2 were produced from vitamin D2 in the absence of pig liver homogenate in vitro was strong evidence for the participation of free radicals in the reaction. Further support for free radical involvement was provided by the following observations: (a) hydroxyl free radical scavengers such as alpha-tocopherol, catalase, and ethanol reduced the amount of 24-OHD2 produced by 18-64%; (b) use of autoclaved homogenate in the incubation mixture had little or no effect on the amount of 24-OHD2 produced; and (c) the failure of the enzyme-substrate saturation curve to level off as expected with high levels of vitamin D2 (100-2000 micrograms = 50-1009 microM). Maximum production of 24-OHD2 was obtained at pH 4.75 and represented a sevenfold increase relative to the amount produced at pH 7.4. The omission of citrate or the addition of electron transport inhibitors, cyanide or antimycin, had little or no effect on the reaction. These data suggested that C-24 hydroxylation of vitamin D2 in vitro was a free radical-mediated process not involving the electron transport system. In vitro hydroxylation at C-24 appeared to be driven by free radicals, and the dominance of this reaction made it difficult to determine whether there was an enzyme involved in the reaction.

Metabolic bone disease of total parenteral nutrition: course after changing from casein to amino acids in parenteral solutions with reduced aluminum content

Bone disease with total parenteral nutrition (TPN) has been attributed to aluminum loading or vitamin D therapy. We studied 17 patients who first received TPN containing casein hydrolysate with high Al and ergocalciferol (25 micrograms/d) for 6-72 mo followed by TPN containing amino acids with reduced Al and ergocalciferol (5 micrograms/d) for 9-58 mo. We also did a cross-sectional study of 22 patients receiving casein and ergocalciferol (25 micrograms/d) compared with 46 patients receiving amino acids and ergocalciferol (5 micrograms/d) for 6-58 mo. Bone formation was higher and osteoid area, bone-surface stainable Al and total bone Al were lower with amino acid TPN than with casein TPN. Bone formation varied inversely with both plasma Al and bone-surface Al, suggesting that plasma or bone-surface Al, acquired during TPN, can reduce bone formation and lead to patchy osteomalacia. Serum levels of iPTH and 1,25-dihydroxyvitamin D were higher with amino acid TPN.

Use of Fourier transform 1H NMR in the identification of vitamin D2 metabolites

The use of Fourier transform 1H NMR to characterize vitamin D2 metabolites is described. A 300-MHz spectrometer capable of generating a 6-microseconds pulse and a sweep width of 4000 Hz was used. High-resolution spectra were obtained on 5 micrograms of material using standard 5-mm NMR tubes fitted with glass inserts and isotopically enriched chloroform-d solvent. The data acquisition time under these conditions was 4 h. Application of this technique to a variety of both synthetic and naturally occurring vitamin D2 metabolites, in addition to synthetic delta 22-1,25-dihydroxyvitamin D3, resulted in the reassignment of the chemical shifts for the C-21 and C-28 methyl groups of vitamin D2. The C-21 methyl group resonance is now assigned to the doublet appearing at delta 1.01, whereas the C-28 signal corresponds to the doublet at delta 0.90. An examination of the spectrum of 24 (R),25-dihydroxyvitamin D2 also led to the reassignment of the side-chain methyl group resonances. This technique is an additional means of identifying microgram quantities of vitamin D metabolites.

Rapid automated high-performance liquid chromatographic assay for ercalcidiol and calcidiol (25-hydroxyvitamins D2 and D3) using trans-calcidiol as an ultraviolet-absorbing internal standard

A system is described using high-performance liquid chromatography to separate and quantify, by spectrophotometry in a simple one-stage procedure, ercalcidiol (25-hydroxyvitamin D2) and calcidiol (25-hydroxyvitamin D3). The novel feature of the method is the employment of an ultraviolet-absorbing internal standard to monitor recovery. This has the advantage of permitting total automation of the quantification by eliminating the need for radioactivity counting. The method gives results that compare well with those obtained in other systems and has particular application in clinical studies where rapid separate determination of ercalcidiol and calcidiol is required.

Lack of evidence for existence of vitamin D and 25-hydroxyvitamin D sulfates in human breast and cow's milk

The presence of water-soluble vitamin D and 25-OH-D sulfates in human breast and cow's milk was studied. We first confirmed that synthetic vitamin D2 and D3 sulfates could not be hydrolyzed by alkali but by acid. Breast or cow's milk was separated into milk whey containing water-soluble components and milk curd containing crude proteins and lipophilic components. The separated milk whey and curd were hydrolyzed by acid or alkali and each lipid extract was subjected to HPLC analysis. Neither peak due to vitamin D and 25-OH-D was observed in the chromatograms of acid- and alkali-hydrolyzed milk whey, whereas the peaks due to vitamin D3 and 25-OH-D3 were found in the chromatograms of both acid- and alkali-hydrolyzed milk curd and there was no significant difference between the respective peak heights. The eluates corresponding to the respective peaks observed on the latter's chromatograms were collected and subjected to UV, HPLC, GC-MS and GLC to identify the existence of vitamin D3 and 25-OH-D3, respectively. We concluded from these results that neither breast nor cow's milk contained water-soluble vitamin D and 25-OH-D sulfates, whereas they contained fat-soluble vitamin D3 and 25-OH-D3. The concentrations of vitamin D3 and 25-OH-D3 in breast milk were about 125 and 350 ng/liter, while those in cow's milk were about 420 and 270 ng/liter, respectively. The experiments on the transfer of 3H-D3 and 3H-25-OH-D3 perorally dosed to lactating rats into suckling pups through their milk also supported the above conclusion.

Relationships among vitamin D, 25-hydroxyvitamin D, and vitamin D-binding protein concentrations in the plasma and milk of human subjects

We measured plasma and milk concentrations of vitamin D2, vitamin D3, 25-hydroxyvitamin D2 (25OHD2), 25-hydroxyvitamin D3 (25OHD3), and vitamin D-binding protein (DBP) in a group of lactating women. All vitamin D compounds were quantitated using competitive protein binding assay, while DBP concentrations were determined by rocket electrophoresis. Vitamin D3 was the most abundant vitamin D compound in human milk, followed by vitamin D2, 25OHD3, and, finally, 25OHD2. The average vitamin D activity in milk was between 33-68 IU/liter, depending on the criterion of biological activity used. DBP concentrations in milk were approximately 3% of those in plasma. Significant relationships were found between plasma and milk levels for all vitamin D compounds. The milk to blood concentration ratio was greatest for vitamin D2, followed by vitamin D3, 25OHD2, and 25OHD3. (Thus, the parent compounds gained access into milk in a much more efficient fashion than their 25-hydroxy metabolites. It is postulated that this differential translocation is controlled by the DBP in the circulation.) There was no significant correlation between plasma and milk DBP concentrations, nor were milk DBP concentrations related to the vitamin D content of milk. This investigation supports the concept that the nutritional status of lactating mothers affects the vitamin D sterol potential of her milk which, in turn, would likely have an effect on the vitamin D status of her nursing infant.