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 (Thomas) the insult, and Hamlet begs forgiveness. The duet affirms their love (Hamlet, Ophélie: "Doute de la lumière" – "Doubt that the light"). The text of the duet is based on Shakespeare's "Doubt thou the stars are fire", which is part of a letter from Hamlet to Ophelia which Polonius reads to Gertrude and Claudius. The melody of the vocal line in Hamlet's first phrases has been called the Theme of Hamlet's Love for Ophélie and appears several more times in the opera, with particular poignancy near the end of the Mad Scene (see below). The three themes which have been