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)2D3, 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. (c) 2007 Published by Elsevier Ltd.