Osmanthus fragrans seeds, a source of secoiridoid glucosides and its antioxidizing and novel platelet-aggregation inhibiting function

Osmanthus fragrans (OF) is widely used as a flavour additive for tea and other beverages in China and some Asian countries. In this paper, phytochemical investigation on OF seed, the purple-brown ripe fruit of OF, resulted in the discovery of a new secoiridoid glucoside, fragranside A (1), together with nine known secoiridoid glucosides (2-10). Their structures were established through 1D and 2D NMR, HRESI-MS spectra, and compared with literature data. By HPLC analysis, nuzhennoside (4) and nuzhennoside G13 (6) were found to be the predominant compounds in OF seeds with a content of 0.87 and 1.23%, respectively. For quality control, they were simultaneously quantified from four representative species of OF seeds. Additionally, antioxidant and antiplatelet aggregation activity of OF seed extracts were first examined. Results showed that OF seed extracts and compounds 4 and 6 had obvious inhibiting effects on platelet aggregation induced by using adenosine 5′-diphosphate (ADP), collagen, and arachidonic acid (AA) as agonists. These findings suggest that OF seeds may have the potential to be developed into a novel inhibitor of platelet aggregation.