Flavonoids that are isolated from plant material of the genus Cecropia can be used to perturb G-protein coupled receptors in a mammalian cell. In some instances, one or more flavonoids may interact with one or more of the G-protein coupled receptors to transiently increase the concentration of cytosolic calcium. Administration of the isolated flavonoids can be used to treat hypertension, to protect the integrity of blood vessels and related conditions.