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 conversation with it as further evidence of madness. After begging the queen to stop sleeping with Claudius, Hamlet leaves, dragging Polonius's corpse away. Hamlet jokes with Claudius about where he has hidden Polonius's body, and the king, fearing for his life, sends Rosencrantz and Guildenstern to accompany Hamlet to England with a sealed letter to the English king requesting that Hamlet be executed immediately. Demented by grief at Polonius's death, Ophelia wanders Elsinore. Laertes arrives back from France, enraged by his father's death and his sister's madness. Claudius convinces Laertes that Hamlet is solely responsible, but a letter soon arrives