Isolation, structural characterization of oligosaccharide AMO-1 from Avicennia marina fruit and its anti-osteoporotic effects via PI3K/AKT/HIF‑1α signaling pathway activation

Avicennia marina (Forssk.) Vierh. is an important mangrove plant with high nutritional and medicinal values, featuring saccharides as its primary bioactive compounds. In this study, we successfully isolated a neutral tetrasaccharide (AMO-1) from the fruits of A. marina. Through monosaccharide composition, methylation, UPLC-ESI-MS/MS, and NMR analyses, we revealed that the structure of AMO-1 was α-D-Galp-(1 → 6)-α-D-Galp-(1 → 6)-α-D-Glcp-(1 → 2)-β-D-Fruf. Subsequently, we investigated the anti-osteoporosis (anti-OP) efficacy and underlying mechanisms of AMO-1. Our findings demonstrated that AMO-1 promoted the differentiation and mineralization of MC3T3-E1 cells. Furthermore, AMO-1 increased trabecular bone density and restored its reticular structure in dexamethasone-induced OP mice. Additionally, AMO-1 upregulated the expression levels of osteogenic factors and elevated serum levels of osteocalcin and PINP. Mechanistically, AMO-1 promoted osteogenesis through activation of the PI3K/AKT/HIF-1α signaling pathway, thus exerting anti-OP effects. Overall, these findings indicate that AMO-1 is a promising functional food ingredient with therapeutic potential for the prevention and management of OP.