<jats:title>Abstract</jats:title><jats:p>A new iridoid alkaloid containing a spirolactone unit, plumericidine (<jats:bold>1</jats:bold>), was isolated from the flowers of <jats:italic>Plumeria rubra</jats:italic> L. <jats:italic>cv. Acutifolia.</jats:italic> Its structure was elucidated by spectroscopic evidence and confirmed by X‐ray diffraction crystallography. Its anticancer and antiviral activities were evaluated, but found to be insignificant.