(2E,6R)-8-Hydroxy-2,6-dimethyl-2-octenoic Acid, a NovelAnti-osteoporotic Monoterpene, Isolated fromCistanche salsa

(2E,6R)-8-Hydroxy-2,6-dimethyl-2-octenoic acid [(R)-HDOA], a novel monoterpene from Cistanche salsa, a Chinese herb, was found to be an anti-osteoporotic compound. The extract of Cistanche salsa significantly suppressed the bone weight loss in ovariectomized mice, a postmenopausal osteoporosis model. The active substance was then purified by using this osteoporotic model and the chemical structure was determined. The active compound from Cistanche salsa, (R)-HDOA, suppressed the decrease of bone weight and the mechanical strength in the ovariectomized mice. Furthermore, (R)- and (S)-HDOA were synthesized and the activity of each was evaluated. (R)-HDOA suppressed the bone weight loss, although (S)-HDOA did not showed any activity.