Radioimmunoassay for rapid estimation of vitamin D derivatives in calcinogenic plants

Targeted delivery of 1,25-dihydroxyvitamin D3 to colon tissue and identification of a major 1,25-dihydroxyvitamin D3 glycoside from Solanumglaucophyllum plant leaves

Leaves of the Solanum glaucophyllum (Sg) plant, indigenous to South America, have long been known for their calcinogenic toxicity in ruminant animals. It was determined the leaves contained glycosidic derivatives of 1,25-dihydroxyvitamin D3 (1,25D3) and liberation of the free hormone by rumen bacterial populations elicited a hypercalcemic response. Our interest in the leaves is predicated on the concept that the glycoside forms of 1,25D3 would target release of the active hormone in the lower gut of non-ruminant mammals. This would provide a means of delivering 1,25D3 directly to the colon, where the hormone has been shown to have beneficial effects in models of inflammatory bowel disease (IBD) and colon cancer. We fed mice for 10 days with variable amounts of Sg leaf. Feeding 7-333μg leaf/day produced no changes in plasma Ca(2+) and 1,25D3 concentrations, and only at ≥1000μg leaf/day did these values become significantly elevated compared to controls. Gene expression studies from colon tissue indicated a linear relationship between the amount of leaf consumed and expression of the Cyp24a1 gene. In contrast, Cyp24a1 gene expression in the duodenums and ileums of these mice was unchanged compared to controls. One of the major 1,25D3-glycosides was isolated from leaves following extraction and purification by Sep-Pak cartridges and HPLC fractionation. Ultraviolet absorbance was consistent with modification of the 1-hydroxyl group, and positive ion ESI mass spectrometry indicated a diglycoside of 1,25D3. 2-Dimensional NMR analyses were carried out and established the C1 proton of the A-ring was interacting with a C1' sugar proton, while the C3 proton of the A-ring was linked with a second C1' sugar proton. The structure of the isolated compound is therefore consistent with a β-linked 1,3-diglycoside of 1,25D3. Thus, Sg leaf administered to mice at up to 333 ug/day can elicit colon-specific enhancement of Cyp24a1 gene expression without inducing hypercalcemia, and the 1,3-diglycoside is one of the major forms of 1,25D3 found in the leaf. This article is part of a Special Issue entitled '17th Vitamin D Workshop'.

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.

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).

Inhibitory effects of morinda officinalis extract on bone loss in ovariectomized rats

The present study was undertaken to investigate the protective effects of ethanol extract from the root of Morinda Officinalis (RMO) on ovariectomy-induced bone loss. Administration of RMO extract increased trabecular bone mineral content and bone mineral density of tibia, improved the levels of phosphorus (P), calcium (Ca) and OPG, decreased the levels of DPD/Cr, TRAP, ACTH and corticosterone, but did not reverse the levels of ALP, TNF-α and IL-6 in serum of ovariectomized rats. These findings demonstrated that RMO extract reduced bone loss in ovariectomized rats, probably via the inhibition of bone resorption, but was not involved with bone formation. Anthraquinones and polysaccharides from Morinda officinals could be responsible for their antiosteoporotic activity, and the action mechanism of these constituents needs to be further studied. Therefore, RMO has the potential to develop a clinically useful antiosteoporotic agent.

Screening of Vitamin D activity (VDA) of Solanum glaucophyllum leaves measured by radioimmunoassay (RIA)

The ingestion of Solanum glaucophyllum (SG) causes a calcinosis of cattle named Enteque Seco (ES). The toxic principle is the 1,25-(OH)(2)D(3), mainly conjugated as glycoside. This study aims to validate a simple novel method of evaluation of the VDA of SG leaves. Aqueous extracts of SG were purified using C(18) minicolumns and assayed by RIA with an antibody raised in rabbits by injection of the acid-C22, 1alpha-(OH)Vitamin D(3). Data were expressed as glycoside equivalent to 1,25-(OH)(2)D(3) in ng/g of dry leaves. We compared this data with 1,25-(OH)(2)D(3) levels measured, in the same samples, by liquid chromatography (HPLC) after enzyme cleavage. This procedure involved the incubation of SG leaves with rumen fluid, followed by C(18)-OH solid phase extraction. The 1,25-(OH)(2)D(3) fraction was run by HPLC and detection was achieved using a photodiode array detector. Data were expressed as micrograms of 1,25-(OH)(2)D(3)/g dry leaves. A significant regression of 1,25-(OH)(2)D(3) levels (Y) as a function of glycoside RIA 1,25-(OH)(2)D(3) equivalents (X) was found: Y=12.02+0.35X [R=0.81; P=0,0002; N=15], allowing us to conclude that this novel assay could be used to estimate the amount of this active principle contained in SG leaves.

Effect of vitamin D-containing plant extracts on osteoporotic bone

Adequate supply of vitamin D(3) is not sufficient for the prevention of post-menopausal osteoporosis, because of a tightly regulated critical step in formation of the most active vitamin D metabolite 1,25-dihydroxyvitamin D(3). Direct application of 1,25(OH)(2)D(3), however, was effective in reducing fracture rate and increasing bone mineral density as has been shown in large clinical studies. Extracts from Solanum glaucophyllum and Trisetum flavescens plants containing 1,25(OH)(2)D(3)-glycosides were characterized by their vitamin D-activity in a quail eggshell bioassay and applied in an osteoporosis model in ovariectomized rats. An extract from the grass T. flavescens and a purified extract from S. glaucophyllum were characterized by the absence of alkaloids and the analytically determined content of 1,25(OH)(2)D(3). In the ovariectomized rat model after 6 months duration, the bone metabolism relevant markers serum calcium, 1,25(OH)(2)D(3), urinary crosslinks and calcium were measured. At termination tibial mineral content was determined and as imaging procedure micro-computerized tomography was applied. The bisphosphonate alendronate was used as a positive standard. While alendronate reduced bone resorption, as seen in a reduced urinary crosslink excretion, both vitamin D metabolite-containing extracts were able to improve bone mineral density by an enhanced calcium turnover.