Medicinal Zingiberaceae in the prevention of menopausal bone loss
In previous studies, well characterized extracts isolated from the dried ground rhizomes of Zingiberaceae plants, including turmeric and ginger, were remarkably protective in preventing bone loss in an animal model of rheumatoid arthritis (RA), preventing up to 80% of bone resorption as assessed by bone mineral density (BMD), normalization of RANK/OPG ratio, and inhibition of osteoclast formation. To determine whether turmeric and ginger might also prevent bone resorption in postmenopausal osteoporosis, their effects on bone were examined in ovariectomized (OVX) rats. Tested botanicals included a curcuminoid-rich fraction of turmeric (94% curcuminoids), a more complex turmeric fraction containing curcuminoids (41%) but devoid of essential oils, and a crude ginger extract containing both gingerols (18%) and essential oils. Three-month female Sprague Dawley rats were placed in the following treatment groups: (1) sham-operated + vehicle; (2) OVX + vehicle; (3) OVX + purified curcuminoids (dosing normalized to 25mg/kg/d curcuminoids), (4) OVX + complex turmeric fraction (25mg/kg/d curcuminoids), and (5) OVX + crude ginger extract (25mg/kg/d gingerols). Effects of 2 months of in vivo extract treatment on bone were determined by BMD analysis using dual-energy x-ray absorptiometry (DXA). OVX animals treated with vehicle lost 12% BMD relative to sham-operated animals following surgery. Treatment with the curcuminoid-rich fraction offered 50% protection against OVX-induced bone loss, while the more chemically complex turmeric fraction protected against 25% of menopausal bone loss. Crude ginger extract protected against only 8% of OVX-induced bone loss. Based on these studies, the curcuminoid-rich turmeric fraction was significantly protective of osteoporotic bone, although the mechanism of bone protection in this model has yet to be elucidated.