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? he'd buy me a fairing should please me, And then for a kiss, oh! he vowed he would tease me, He promised he'd bring me a bunch of blue ribbons, To tie up my bonny brown hair. </poem> Cohen's "Folk Music" gives a different version of the lyrics: <poem> O dear, what can the matter be? O dear, what can the matter be? O dear, what can the matter be? Johnny's so long at the fair. He promised he'd bring me a bunch of blue ribbons. He promised he'd bring me a bunch of blue ribbons. He promised he'd bring