Vitamin D3 and its metabolites in the tomato plant

Organic Synthesis of New Secosteroids from Fucosterol, Its Intestinal Absorption by Caco-2 Cells, and Simulation of the Biological Activities of Vitamin D

We previously examined the cellular uptake of six types of vitamin D in human intestinal Caco-2 cells. Since vitamins D5-D7 were commercially unavailable, we synthesized these compounds organically before studying them. This process led us to understand that new secosteroids could be generated as vitamin D candidates, depending on the sterol used as the starting material. We obtained two new secosteroids-compounds 3 and 4-from fucosterol in the current study. We investigated the intestinal absorption of these compounds using Caco-2 cells cultured in Transwells and compared the results with vitamin D3, a representative secosteroid. The intestinal absorption of compound 4 was comparable to that of vitamin D3. Compound 3 showed similar uptake levels but transported about half as much as vitamin D3. These compounds demonstrated intestinal absorption at the cellular level. Vitamin D is known for its diverse biological activities manifest after intestinal absorption. Using PASS online simulation, we estimated the biological activity of compound 3's activated form. In several items indicated by PASS, compound 3 exhibited stronger biological activity than vitamins D2-D7 and was also predicted to have unique biological activities.

Uptake of Vitamins D2, D3, D4, D5, D6, and D7 Solubilized in Mixed Micelles by Human Intestinal Cells, Caco-2, an Enhancing Effect of Lysophosphatidylcholine on the Cellular Uptake, and Estimation of Vitamins D' Biological Activities

Vitamins D have various biological activities, as well as intestinal calcium absorption. There has been recent concern about insufficient vitamin D intake. In addition to vitamins D₂ and D₃, there are lesser-known vitamins D₄–D₇. We synthesized vitamins D₅–D₇, which are not commercially available, and then evaluated and compared the mixed micelles-solubilized vitamins D uptake by Caco-2 cells. Except for vitamin D₅, the uptake amounts of vitamins D₄–D₇ by differentiated Caco-2 cells were similar to those of vitamins D₂ and D₃. The facilitative diffusion rate in the ezetimibe inhibited pathway was approximately 20% for each vitamin D type, suggesting that they would pass through the pathway at a similar rate. Lysophosphatidylcholine enhanced each vitamin D uptake by approximately 2.5-fold. Lysophosphatidylcholine showed an enhancing effect on vitamin D uptake by reducing the intercellular barrier formation of Caco-2 cells by reducing cellular cholesterol, suggesting that increasing the uptakes of vitamins D and/or co-ingesting them with lysophosphatidylcholine, would improve vitamin D insufficiency. The various biological activities in the activated form of vitamins D₄–D₇ were estimated by Prediction of Activity Spectra for Substances (PASS) online simulation. These may have some biological activities, supporting the potential as nutritional components.

Increased Consumption of Plant Foods Is Associated with Increased Bone Mineral Density

OBJECTIVES

To determine the relationship between plant food consumption and bone mineral density (BMD) in a healthy population when age, gender, BMI and physical activity are accounted for.

DESIGN

Cross-sectional study.

SETTING

Participants were recruited from the Sydney Adventist hospital and the University of New South Wales, Sydney, Australia.

PARTICIPANTS

33 males and 40 females (total n=73) participated in this study. The mean age was 56.1 ± 8.5 years. All participants were non-diabetic and in general good health.

MEASUREMENTS

A principle component analysis (PCA) was performed on 12 month self-report food intake data, gathered using the Cancer Council Victoria Dietary Questionnaire for Epidemiological Studies Version 2. Dual-energy X-ray absorptiometry was used to measure total BMD. Fasting plasma total protein, calcium and 25-Hydroxy Vitamin D levels were analysed by the Sydney Adventist Hospital pathology laboratory. Anthropometric measures were obtained using a standardized protocol. Self-reported physical activity levels were assessed using the International Physical Activity Questionnaire.

RESULTS

The PCA revealed three principle components. These were termed 'Meat Based', 'Junk Food' and 'Plant Based.' After controlling for age, gender, physical activity and BMI, the Plant Based component correlated positively with BMD (p=0.054, R2=0.439) and T-score (p=0.053, R2=0.221). Using a similar model no association between the Meat Based component and BMD or T-score was found. However, when the Plant Based component was included the Meat Based component correlated positively with BMD (p=0.046, R2=0.474) and T-score (p=0.046, R2=0.279). There was no significant association between the Junk Food component and BMD or T-score. People in the third Plant (927 ± 339 vs 751 ± 255 g/day, p=0.025) and Meat Based (921 ± 270 vs 676 ± 241 g/day, p=0.002) tertile had higher calcium intakes than those in the first. People in the second Plant Based tertile had higher plasma Vitamin D levels than those in the first (63.5 ± 16.8 vs. 52.3 ± 22.1 nmol/L, p=0.053) while those in the third Junk Food tertile had lower levels than those in the first (52.4 ± 18.5 vs. 65.4 ± 19.8 nmol/L, p=0.027). No association between Plant Based tertiles and protein intake was observed, however those in the third Meat Based (99.7 ± 25.1 vs. 50.9 ± 13.8 g/day, p=0.000) and Junk Food (87.4 ± 30.7 vs. 56.6 ± 22.2 g/day, p=0.000) tertile had higher protein intake compared to those in the first tertile.

CONCLUSION

In a healthy middle aged population with normal BMD, an increase in plant food consumption, either alone or in combination with a diet containing meat, is associated with improved bone mineralisation markers. This positive relationship is most likely due to the extensive range of micronutrients and phytochemicals packaged within plants.

Evolutionary Perspective in Rickets and Vitamin D

Modern lifestyle limits our exposure to sunlight, which photosynthesizes vitamin D in the skin, and the incidence of nutritional rickets has been resurging. Vitamin D is one of the first hormones; it is photosynthesized in all organism from the phytoplankton to mammals. A selective sweep of the promoter of the vitamin D receptor (VDR) happened as soon as Homo sapiens migrated out of Africa; it co-adapted with skin color genes to provide adaptation to latitudes and the levels of exposure to ultraviolet (UV)B radiation along the route out of Africa. Exposure to UVB radiation balances the need for vitamin D photosynthesis and degradation of folic acid by UVB radiation. Skin color follows a latitude distribution: the darkest populations dwell in the tropical belt; and the fair-skinned populations inhabit the northern countries. Due to their greater need for calcium during their reproductive life, the skin color of women is lighter- than that of men. Vitamin D is essential for mineral homeostasis and has a wide variety of non-skeletal functions, of which the most important for natural selection is a regulatory function in the innate immune system. In the human fossil record, vitamin D deficiency coincided with bone tuberculosis. About 6,000 years ago, a diet which included cow's milk provided Neolithic humans with twice as much calcium and was more alkaline than that of its Paleolithic predecessors. Adiposity is negatively associated with the vitamin D status and obese individuals require 2-3 times more vitamin D than non-obese individuals to normalize circulating 25OHD levels. In an era of an obesity epidemic, we need more research to determine whether adiposity should be considered when determining the dietary requirements for vitamin D and calcium and the optimal serum 25OHD levels.

Vitamin D5 in Arabidopsis thaliana

Vitamin D₃ is a secosterol hormone critical for bone growth and calcium homeostasis, produced in vertebrate skin by photolytic conversion of the cholesterol biosynthetic intermediate provitamin D₃. Insufficient levels of vitamin D₃ especially in the case of low solar UV-B irradiation is often compensated by an intake of a dietary source of vitamin D₃ of animal origin. Small amounts of vitamin D₃ were described in a few plant species and considered as a peculiar feature of their phytochemical diversity. In this report we show the presence of vitamin D₅ in the model plant Arabidopsis thaliana. This plant secosterol is a UV-B mediated derivative of provitamin D₅, the precursor of sitosterol. The present work will allow a further survey of vitamin D distribution in plant species.

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.

Vitamin D Content of Australian Native Food Plants and Australian-Grown Edible Seaweed

Vitamin D has previously been quantified in some plants and algae, particularly in leaves of the Solanaceae family. We measured the vitamin D content of Australian native food plants and Australian-grown edible seaweed. Using liquid chromatography with triple quadrupole mass spectrometry, 13 samples (including leaf, fruit, and seed) were analyzed in duplicate for vitamin D₂, vitamin D₃, 25-hydroxyvitamin D₂, and 25-hydroxyvitamin D₃. Five samples contained vitamin D₂: raw wattleseed (Acacia victoriae) (0.03 µg/100 g dry weight (DW)); fresh and dried lemon myrtle (Backhousia citriodora) leaves (0.03 and 0.24 µg/100 g DW, respectively); and dried leaves and berries of Tasmanian mountain pepper (Tasmannia lanceolata) (0.67 and 0.05 µg/100 g DW, respectively). Fresh kombu (Lessonia corrugata) contained vitamin D₃ (0.01 µg/100 g DW). Detected amounts were low; however, it is possible that exposure to ultraviolet radiation may increase the vitamin D content of plants and algae if vitamin D precursors are present.

In Pursuit of Vitamin D in Plants

Vitamin D deficiency is a global concern. Much research has concentrated on the endogenous synthesis of vitamin D in human skin following exposure to ultraviolet-B radiation (UV-B, 280–315 nm). In many regions of the world there is insufficient UV-B radiation during winter months for adequate vitamin D production, and even when there is sufficient UV-B radiation, lifestyles and concerns about the risks of sun exposure may lead to insufficient exposure and to vitamin D deficiency. In these situations, dietary intake of vitamin D from foods or supplements is important for maintaining optimal vitamin D status. Some foods, such as fatty fish and fish liver oils, certain meats, eggs, mushrooms, dairy, and fortified foods, can provide significant amounts of vitamin D when considered cumulatively across the diet. However, little research has focussed on assessing edible plant foods for potential vitamin D content. The biosynthesis of vitamin D in animals, fungi and yeasts is well established; it is less well known that vitamin D is also biosynthesised in plants. Research dates back to the early 1900s, beginning with in vivo experiments showing the anti-rachitic activity of plants consumed by animals with induced rickets, and in vitro experiments using analytical methods with limited sensitivity. The most sensitive, specific and reliable method for measuring vitamin D and its metabolites is by liquid chromatography tandem mass spectrometry (LC-MS/MS). These assays have only recently been customised to allow measurement in foods, including plant materials. This commentary focuses on the current knowledge and research gaps around vitamin D in plants, and the potential of edible plants as an additional source of vitamin D for humans.

Plant Oils as Potential Sources of Vitamin D

To combat vitamin D insufficiency in a population, reliable diet sources of vitamin D are required. The recommendations to consume more oily fish and the use of UVB-treated yeast are already applied strategies to address vitamin D insufficiency. This study aimed to elucidate the suitability of plant oils as an alternative vitamin D source. Therefore, plant oils that are commonly used in human nutrition were first analyzed for their content of vitamin D precursors and metabolites. Second, selected oils were exposed to a short-term UVB irradiation to stimulate the synthesis of vitamin D. Finally, to elucidate the efficacy of plant-derived vitamin D to improve the vitamin D status, we fed UVB-exposed wheat germ oil (WGO) for 4 weeks to mice and compared them with mice that received non-exposed or vitamin D3 supplemented WGO. Sterol analysis revealed that the selected plant oils contained high amounts of not only ergosterol but also 7-dehydrocholesterol (7-DHC), with the highest concentrations found in WGO. Exposure to UVB irradiation resulted in a partial conversion of ergosterol and 7-DHC to vitamin D2 and D3 in these oils. Mice fed the UVB-exposed WGO were able to improve their vitamin D status as shown by the rise in the plasma concentration of 25-hydroxyvitamin D [25(OH)D] and the liver content of vitamin D compared with mice fed the non-exposed oil. However, the plasma concentration of 25(OH)D of mice fed the UVB-treated oil did not reach the values observed in the group fed the D3 supplemented oil. It was striking that the intake of the UVB-exposed oil resulted in distinct accumulation of vitamin D2 in the livers of these mice. In conclusion, plant oils, in particular WGO, contain considerable amounts of vitamin D precursors which can be converted to vitamin D via UVB exposure. However, the UVB-exposed WGO was less effective to improve the 25(OH)D plasma concentration than a supplementation with vitamin D3.

Vitamin D: Photobiological and Ecological Aspects

Vitamin D was discovered as a result of its ability to cure rickets, but recently a wide range of other functions for it in the human body has been suggested. Vitamin D is not a vitamin in the strict sense as it can be synthesised in the human body following exposure of the skin to ultraviolet radiation. Provitamin D (7-dehydrocholesterol) is converted to previtamin D which is further modified by a series of reactions to the active form, 1,25-dihydroxyvitamin D. This Chapter summarises the discovery of vitamin D and reviews the chemistry and photochemistry of its precursors, transformations and metabolites. The production of vitamin D in various human populations is described, and how to assess vitamin D status. The skeletal and non-skeletal effects of vitamin D are discussed, particularly its role in immunomodulation with consequences for protection against a variety of human diseases. The Chapter concludes with evolutionary aspects, the occurrence and role of vitamin D in the plant kingdom, biogeographical considerations, and the nonphotochemical production of vitamin D in certain plants.

Vitamin D: calcium and bone homeostasis during evolution

Vitamin D3 is already found early in the evolution of life but essentially as inactive end products of the photochemical reaction of 7-dehydrocholestol with ultraviolet light B. A full vitamin D (refers to vitamin D2 and D3) endocrine system, characterized by a specific VDR (vitamin D receptor, member of the nuclear receptor family), specific vitamin D metabolizing CYP450 enzymes regulated by calciotropic hormones and a dedicated plasma transport-protein is only found in vertebrates. In the earliest vertebrates (lamprey), vitamin D metabolism and VDR may well have originated from a duplication of a common PRX/VDR ancestor gene as part of a xenobiotic detoxification pathway. The vitamin D endocrine system, however, subsequently became an important regulator of calcium supply for an extensive calcified skeleton. Vitamin D is essential for normal calcium and bone homeostasis as shown by rickets in vitamin D-deficient growing amphibians, reptiles, birds and mammals. From amphibians onward, bone is gradually more dynamic with regulated bone resorption, mainly by combined action of PTH and 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3) on the generation and function of multinucleated osteoclasts. Therefore, bone functions as a large internal calcium reservoir, under the control of osteoclasts. Osteocytes also display a remarkable spectrum of activities, including mechanical sensing and regulating mineral homeostasis, but also have an important role in global nutritional and energy homeostasis. Mineralization from reptiles onward is under the control of well-regulated SIBLING proteins and associated enzymes, nearly all under the control of 1,25(OH)2D3. The vitamin D story thus started as inert molecule but gained an essential role for calcium and bone homeostasis in terrestrial animals to cope with the challenge of higher gravity and calcium-poor environment.

Vitamin D in plants: a review of occurrence, analysis, and biosynthesis

The major function of vitamin D in vertebrates is maintenance of calcium homeostasis, but vitamin D insufficiency has also been linked to an increased risk of hypertension, autoimmune diseases, diabetes, and cancer. Therefore, there is a growing awareness about vitamin D as a requirement for optimal health. Vitamin D3 is synthesized in the skin by a photochemical conversion of provitamin D3, but the necessary rays are only emitted all year round in places that lie below a 35° latitude. Unfortunately, very few food sources naturally contain vitamin D and the general population as a results fail to meet the requirements. Fish have the highest natural content of vitamin D expected to derive from an accumulation in the food chain originating from microalgae. Microalgae contain both vitamin D3 and provitamin D3, which suggests that vitamin D3 exist in the plant kingdom and vitamin D3 has also been identified in several plant species as a surprise to many. The term vitamin D also includes vitamin D2 that is produced in fungi and yeasts by UVB-exposure of provitamin D2. Small amounts can be found in plants contaminated with fungi and traditionally only vitamin D2 has been considered present in plants. This review summarizes the current knowledge on sterol biosynthesis leading to provitamin D. It also addresses the occurrence of vitamin D and its hydroxylated metabolites in higher plants and in algae and discusses limitations and advantages of analytical methods used in studies of vitamin D and related compounds including recent advances in analytical technologies. Finally, perspectives for a future production of vitamin D biofortified fruits, vegetables, and fish will be presented.

Altitude, pasture type, and sheep breed affect bone metabolism and serum 25-hydroxyvitamin D in grazing lambs

This study aimed to investigate the bone development of two mountain sheep breeds during natural summer grazing either in the lowlands or on different characteristic alpine pastures. Pasture types differed in topographic slope, plant species composition, general nutritional feeding value, Ca and P content, and Ca:P ratio of herbage. Twenty-seven Engadine sheep (ES) lambs and 27 Valaisian Black Nose sheep (VS) lambs were divided into four groups of 6 to 7 animals per breed and allocated to three contrasting alpine pasture types and one lowland pasture type. The lambs were slaughtered after 9 wk of experimental grazing. The steep alpine pastures in combination with a high (4.8) to very high (13.6) Ca:P ratio in the forage decreased total bone mineral content as measured in the middle of the left metatarsus of the lambs from both breeds, and cortical bone mineral content and cortical bone mineral density of ES lambs. Breed × pasture type interactions occurred in the development of total and cortical bone mineral content, and in cortical thickness, indicating that bone metabolism of different genotypes obviously profited differently from the varying conditions. An altitude effect occurred for 25-hydroxyvitamin D with notably higher serum concentrations on the three alpine sites, and a breed effect led to higher concentrations for ES than VS. Despite a high variance, there were pasture-type effects on serum markers of bone formation and resorption.

Quantification of vitamin D3 and its hydroxylated metabolites in waxy leaf nightshade (Solanum glaucophyllum Desf.), tomato (Solanum lycopersicum L.) and bell pepper (Capsicum annuum L.)

Changes in vitamin D(3) and its metabolites were investigated following UVB- and heat-treatment in the leaves of Solanum glaucophyllum Desf., Solanum lycopersicum L. and Capsicum annuum L. The analytical method used was a sensitive and selective liquid chromatography electrospray ionisation tandem mass spectrometry (LC-ESI-MS/MS) method including Diels-Alder derivatisation. Vitamin D(3) and 25-hydroxy vitamin D(3) were found in the leaves of all plants after UVB-treatment. S. glaucophyllum had the highest content, 200 ng vitamin D(3)/g dry weight and 31 ng 25-hydroxy vitamin D(3)/g dry weight, and was the only plant that also contained 1,25 dihydroxy vitamin D(3) in both free (32 ng/g dry weight) and glycosylated form (17 ng/g dry weight).

Alternative therapies for the prevention and treatment of osteoporosis

Osteoporosis is a medical condition that affects millions of men and women. People with this condition have low bone mass, which places them at increased risk for bone fracture after minor trauma. The surgeries and treatments required to repair and heal bone fractures involve long recovery periods and can be expensive. Because osteoporosis occurs frequently in the elderly, the financial burden it places on society is likely to be large. In the United States, the Food and Drug Administration has approved several drugs for use in the prevention and treatment of osteoporosis. However, all of the currently available agents have severe side effects that limit their efficacy and underscore the urgent need for new treatment options. One promising approach is the development of alternative (nonpharmaceutical) strategies for bone maintenance, as well as for the prevention and treatment of osteoporosis. This review examines the currently available nonpharmaceutical alternatives that have been evaluated in in vitro and in vivo studies. Certain plants from the following families have shown the greatest benefits on bone: Alliceae, Asteraceae, Thecaceae, Fabaceae, Oleaceae, Rosaceae, Ranunculaceae, Vitaceae, Zingiberaceae. The present review discusses the most promising findings from studies of these plant families.

Vitamin D: an ancient hormone

Vitamin D has been produced by plants and animals almost from the time life began. The ability to transport and metabolize vitamin D to more active forms evolved as the structures of plants and animals became more complex, and the cells within these organisms took on more specialized functions. In higher-order animals, the vitamin D receptor (VDR) is found in nearly every cell, and the ability of the cell to produce the active hormone, 1,25(OH)2D, is also widely distributed. Furthermore, the physiological functions with which vitamin D signalling is now associated are as diverse as the tissues in which the VDR is located. Why is this, and is there a common theme? This viewpoint article argues that there is. All cells maintain a fairly constant and submicromolar concentration of free calcium. Calcium is an important regulator of many processes within the cell. The ebb and flow of calcium within cells is controlled by calcium pumps, antiporters and channels. Animals with calcified exo- or endoskeletons have an additional need for calcium, a need that changes during the life cycle of the organism. In this article, I make the case that vitamin D signalling evolved to enable the organism to effectively regulate calcium flux, storage and signalling and that such regulation is critical for the evolutionary process.

Effect of culture conditions on the synthesis of vitamin D(3) metabolites in Solanum glaucophyllum grown in vitro

In cultured Solanum glaucophyllum we have recently described the operation of a light-independent pathway of 1alpha,25-dihydroxy-vitamin D(3) (1alpha,25(OH)(2)D(3)) biosynthesis which involves similar intermediates as in vertebrates. In this work we investigated factors influencing the formation of 1alpha,25(OH)(2)D(3) and related sterols in S. glaucophyllum grown in vitro in darkness. Callus tissue and cells cultured in Murashige and Skoog medium in the absence of light were employed. Lipids were extracted with chloroform-methanol. The remaining water soluble fraction was incubated with beta-glucosidase to release vitamin D(3) compounds from their glycoconjugated derivatives followed by organic solvent extraction. Vitamin D(3) derivatives were isolated by Sephadex LH-20 and high-performance liquid chromatography (HPLC). HPLC or competitive protein binding assays with intestine 1alpha,25(OH)(2)D(3) receptor and serum vitamin D binding protein were used to quantify the metabolites. The levels of 1alpha,25(OH)(2)D(3) in calli varied according to the tissue explant origin, e.g. stem>leaf>fruit. For all organs, the metabolite was mainly present as free sterol (>80% of total). There were larger amounts of 25(OH)D(3) than 1alpha,25(OH)(2)D(3). It was found that Ca(2+), auxin and kinetin are important factors upregulating 1alpha,25(OH)(2)D(3) synthesis in S. glaucophyllum tissue and cells. Irradiation with UV light increased vitamin D(3) but not 1alpha,25(OH)(2)D(3) levels. In agreement with these results, incubation of cells with [3H]25(OH)D(3) revealed a low conversion rate to [3H]1alpha,25(OH)(2)D(3). The operation of a light-dependent pathway formation of vitamin D(3) coupled to higher expression of 25(OH)D(3)-1alpha-hydroxylase may account for the large concentrations of 1alpha,25(OH)(2)D(3) normally found in differentiated field-grown plants.

Provitamins and vitamins D₂and D₃in Cladina spp. over a latitudinal gradient: possible correlation with UV levels

Provitamin D2, vitamin D2 and vitamin D3 were identified in the thallus of a lichen species, Cladina arbuscula (Wallr.) Hale and W.L. Culb. The identification of vitamin D3 was supported by: (1) co-chromatography in both reverse and straight phase HPLC (high performance liquid chromatography), (2) ultraviolet absorption spectrum, and (3) molecular ion peaks demonstrated by ESI (electrospray ionisation) mass spectrometry. The contents of vitamin D3 range from 0.67 to 2.04 μg g⁻¹ dry matter in the thalli of C. arbuscula specimens grown under different natural conditions, while provitamin D3 could not be detected. The ranges for provitamin D2 and vitamin D2 were 89-146 and 0.22-0.55 μg g⁻¹ dry matter, respectively, while the contents of provitamin D3 were below the detection limit (0.01 microg g(-1) dry matter). When C. arbuscula thalli collected at different latitudes from northern Finland to Greece were compared, a positive correlation of vitamin D2 and D3 contents with modelled UV-B radiation at the collection sites was found. A single sample of C. rangiferina from northern Finland gave much higher values for the vitamins. A possible reason could be the lower content of UV-B absorbing pigment in the latter species.

Nicotiana glauca: another plant species containing vitamin D(3) metabolites

Vitamin D(3)-related compounds have been detected in various plant species, mostly belonging to the Solanaceae. In this work we show that Nicotiana glauca, a widespread member of this taxonomic family, contains 7-dehydrocholesterol, vitamin D(3) and hydroxylated derivatives bearing precursor-product metabolic relationships in vertebrates. Leaves collected in the field and callus cultures were used. By means of specific radioreceptor binding assays and mass spectrometry of purified fractions obtained from plant tissue lipid extracts by Sephadex LH-20 and Sep-Pak C18 chromatography followed by HPLC, we established the presence of 7-dehydrocholesterol, vitamin D(3), 25(OH)-vitamin D(3) and 1alpha,25(OH)(2)-vitamin D(3) (1alpha,25(OH)(2)D(3)), the latter being a hormonally relevant metabolite in animals. These results indicate that N. glauca may represent a useful species in which to characterize the biosynthetic pathway and physiological functions of vitamin D(3) compounds in plants. In addition, tissue culture of N. glauca could become a significant tool for biotechnological production of 1alpha,25(OH)(2)D(3).