Calophyllum inophyllum is a coastal plant rich in natural substances. Its ingredients have been used for the development of an anti-human immunodeficiency virus (HIV) drug. In this study, we collected C. inophyllum fruit, and the ethanol extract of the fruit was chromatographically separated using silica gel and Sephadex LH-20 columns to obtain the major compound, calophyllolide. The fruits were harvested from September to December in 2011; a quantitative analysis of the calophyllolide content was conducted using HPLC to explore the differences between the different parts of the fruit during the growing season. The results showed that in fruits of C. inophyllum, calophyllolide exists only in the nuts, and dried nuts contain approximately 2 mg·g −1 of calophyllolide. The calophyllolide levels in the nuts decreased during maturity. In addition, calophyllolide dose-dependently OPEN ACCESSMolecules 2015, 20 12315 enhanced alkaline phosphatase (ALP) activity in murine osteoblastic MC3T3-E1 cells, without significant cytotoxicity. The expression of osteoblastic genes, ALP and osteocalcin (OCN), were increased by calophyllolide. Calophyllolide induced osteoblasts differentiation also evidenced by increasing mineralization and ALP staining.