Effects of Dried Plum Polyphenol Extract on Bone Formation

Abstract

Our earlier findings indicate that dried plums are highly effective in preventing and reversing ovarian hormone deficiency-associated bone loss in a rat model of osteoporosis. Moreover, our short-term clinical trial showed that dried plum supplementation significantly increased indices of bone formation in postmenopausal women. The bone protective effect of dried plum, in part, may be due to its polyphenol content. The intent of the present study was to investigate the bone formation mechanisms of action of polyphenol extracted from dried plum using a cell culture system. We hypothesized that polyphenol extract from dried plum increases bone mineralization in MC3T3-E1 cell line. Also we hypothesized that polyphenol extract decrease pro-inflammatory molecules in macrophages. MC3T3-E1 cells were treated with various doses of polyphenol extract (0, 0.5, 1, 10, 100, 1000 �g/ml). Media was collected every three days and analyzed for alkaline phosphatase activity. After 14 days, the formation of mineralized nodules was characterized by Alizarin red staining. Our findings indicate that dried plum polyphenol dose-dependently increases mineralization without affecting cell viability as shown by resazurin assay. Alkaline phosphatase activity was significantly increased at days six and nine. Among the doses tested, 100 �g/ml of polyphenol extract caused a significant elevation of alkaline phosphatase activity. For the second objective macrophages were stimulated with 100 ng/ml LPS and then they were treated with (1, 10, 100, and 1000 �g/ml) polyphenol extract. Result showed that polyphenol extract decreased the production of pro-inflammatory molecules such as COX-2 and nitric oxide in macrophages. Overall, the finding of the present study suggests that dried plum polyphenol extract enhances bone formation and suppresses the production of inflammatory molecules known to be harmful to bone.