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):
Prince Hamlet Polonius persuade Ophelia—Polonius' daughter and Hamlet's true love—to speak with Hamlet while they secretly listen. Hamlet enters, contemplating suicide ("To be, or not to be"). Ophelia greets him, and offers to return his remembrances, upon which Hamlet questions her honesty and tells her to "get thee to a nunnery." Hamlet devises a test to see whether Claudius is guilty: he hires a group of actors to perform a play about the murder of a king in front of the royal court, and has Horatio gauge Claudius' reaction. Claudius demands the play be stopped half through because it is the cause