Ruta graveolens the isolation of the furanocoumarin chalepensin. The essential oil of "R. graveolens" contains two main constituents, undecan-2-one (46.8%) and nonan-2-one (18.8%). The bitter taste of its leaves led to rue being associated with the (etymologically unrelated) verb "rue" "to regret". Rue is well known for its symbolic meaning of regret and it has sometimes been called "herb-of-grace" in literary works. It is one of the flowers distributed by the mad Ophelia in William Shakespeare's "Hamlet" (IV.5): It was planted by the gardener in "Richard II" to mark the spot where the Queen wept upon hearing news of Richard's capture (III.4.104–105):
Hamlet letters and tokens of affection to the prince while he and Claudius watch from afar to evaluate Hamlet's reaction. Hamlet is walking alone in the hall as the King and Polonius await Ophelia's entrance, musing whether "to be or not to be". When Ophelia enters and tries to return Hamlet's things, Hamlet accuses her of immodesty and cries "get thee to a nunnery", though it is unclear whether this, too, is a show of madness or genuine distress. His reaction convinces Claudius that Hamlet is not mad for love. Shortly thereafter, the court assembles to watch the play Hamlet has