Discovery, Characterization, and Anti-XOD Activity of Calcium Metallophore from Coix lacryma-jobi

In this work, coixalkyne A (1), a natural polynuclear calcium complex with a novel cross-shaped molecular architecture, was isolated from Coix lacryma-jobi L. along with the undescribed analogue coixalkyne B (2). Their structures were identified by means of NMR spectroscopy, ECD calculations, and single-crystal X-ray diffraction. It is noteworthy that the calcium ligands of 1 as well as compound 2 possess rare terminal alkynes and a nor-carbon sesquiterpene (C14) framework. The antihyperuricemic activity of C. lacryma-jobi and xanthine oxidase (XOD) inhibitory effects of 1-2 were elucidated by in vivo and in vitro assays, while the possible mechanism of action was suggested by molecular docking. Different from the reported chemical synthesis and protein calcium carriers, the discovery of compounds 1 and 2 provided new proof for the natural calcium metallophore in plants with xanthine oxidase inhibitory activity.