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):
Oh Dear! What Can the Matter Be? me a twopenny whistle He'll buy me a threepenny fair He'll buy me a Bunch o' Blue Ribbons To tye up my bonny Brown Hair O saw ye him coming And saw ye him coming O saw ye him coming Hame frae the Newcastle fair </poem> The following are given as the traditional lyrics (being chorus and verse) in Cuddon's and Preston's "A Dictionary of Literary Terms and Literary Theory": <poem> O dear, what can the matter be? Dear, dear, what can the matter be? O dear, what can the matter be? Johnny's so long at the fair. He promised