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 the deaths of his love Ophelia (drowning) and of his mother Gertrude (poisoned by Claudius by mistake). The play opens with Hamlet deeply depressed over the recent death of his father, King Hamlet, and his uncle Claudius' ascension to the throne and hasty marriage to Hamlet's mother Gertrude. One night, his father's ghost appears to him and tells him that Claudius murdered him in order to usurp the throne, and commands his son to avenge his death. Claudius sends for two of Hamlet's friends from Wittenberg, to find out what is causing Hamlet so much pain. Claudius and his advisor