Isolation of Osteoblastic Differentiation-Inducing Constituents from Peanut Sprouts and Development of Optimal Extraction Method

Osteoporosis, one of the most common bone diseases, results from an imbalance between bone formation and resorption. Osteoblasts are primarily involved in bone formation, whereas osteoclasts are involved in bone resorption. Therefore, any substances that can increase osteoblastic differentiation would be beneficial for the prevention or treatment of osteoporosis. In this study, peanut sprouts, a germinated product of peanuts, significantly enhanced osteoblastic differentiation of pre-osteoblastic MC3T3-E1 cells, as determined by the alkaline phosphatase (ALP) assay. The ethyl acetate fraction of peanut sprout extract was subjected to diverse column chromatographies using silica gel, ODS, and Sephadex LH-20 as stationary phases, and three nucleobases, namely, adenine, uracil, and thymine, and three phenolic acids, including caffeic acid, coumaric acid, and ferulic acid, were isolated as active constituents. In particular, adenine at 4 μg/mL and caffeic acid at 1 μg/mL increased ALP activity by 40 and 30%, respectively, compared with the osteoblastic differentiation medium-treated group, and these two compounds were set as marker compounds. Furthermore, extraction of peanut sprouts grown for 14–17 days with 60% ethanol was the best condition to obtain a high quantity of extract for peanut sprouts by analyzing the contents of marker compounds through HPLC. Together, these results suggest that peanut sprouts and their isolated compounds significantly enhance osteoblastic differentiation. Therefore, peanut sprouts have the potential to be developed as functional foods against osteoporosis.