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 reject his advances. That night on the rampart, the ghost appears to Hamlet, telling the prince that he was murdered by Claudius and demanding that Hamlet avenge him. Hamlet agrees and the ghost vanishes. The prince confides to Horatio and the sentries that from now on he plans to "put an antic disposition on", or act as though he has gone mad, and forces them to swear to keep his plans for revenge secret. Privately, however, he remains uncertain of the ghost's reliability. Soon thereafter, Ophelia rushes to her father, telling him that Hamlet arrived at her door the prior