BMP2-Binding Caffeoylquinic Acids from Periploca forrestii Promote Osteoblast Differentiation via Smad Signaling Activation

The BMP2-Smad signaling pathway serves as a central regulator of osteoblast differentiation and bone formation, rendering it a promising target for the discovery of osteogenic agents from natural sources. Nonetheless, direct BMP2-binding ligands derived from complex herbal extracts remain poorly characterized. In the present study, surface plasmon resonance (SPR)-based target fishing against BMP2, in conjunction with UPLC-Q-TOF-MS identification, was employed to screen for bioactive ligands from Periploca forrestii, a traditional Miao medicinal plant used for bone-related conditions. Six caffeoylquinic acid derivatives, namely neochlorogenic acid (NCA), 3-O-caffeoyl-4-O-sinapoylquinic acid, chlorogenic acid (CA), cryptochlorogenic acid (CCA), isochlorogenic acid B (IB), and isochlorogenic acid C (IC), were captured as direct BMP2-binding ligands. All six compounds promoted osteoblast differentiation and mineralization in MC3T3-E1 Subclone 14 cells, with IB displaying the strongest binding affinity and bioactivity. Mechanistically, IB failed to rescue the osteogenic suppression induced by the BMP type I receptor inhibitor LDN-193189, indicating its dependence on BMP signaling. In an LPS-induced inflammatory model, IB significantly reversed the downregulation of key proteins in the BMP2-Smad pathway (p-Smad1, Smad4, and Runx2) and osteogenic marker genes (Osterix, COL1A1, and OCN), demonstrating its capacity to restore osteogenic function under compromised conditions. Collectively, these findings establish that caffeoylquinic acid derivatives, particularly IB, function as BMP2-targeting osteogenic constituents of P. forrestii that activate BMP2-Smad signaling to promote osteoblast differentiation, thereby offering a pharmacological basis for the development of natural product-derived osteogenic agents.