The Oxygen Heterocyclic Compounds of Citrus Peel Oils

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Abstract
The occurrence of oxygen heterocyclic compounds in the peel oils from different Citrus species has been investigated by high performance liquid chromatography. The use of a photodiode array detector has facilitated the identification and quantification of the individual coumarins, psoralens and polymethoxyflavones present. Certain oxygen heterocyclic compounds are unique to a particular species, but the majority occur widely in the peel oils. Nevertheless, the patterns of occurrence are sufficiently diverse to permit the detection of peel oil from one species in that from another. 7-Methoxycoumarin (herniarin) has been identified as a natural component of both Persian and Key lime oil. The presence of herniarin in commercial samples of lemon oil now is attributed to the addition of lime oil to these oils. Other compounds identified in the present study and reported for the first time as components of citrus peel oils include isomeranzin (bitter orange and grapefruit), 8-(2′,3′-epoxyisopentyloxy)psoralen and 8-methoxy-5-(2′, 3′ -epoxyisopentyloxy)psoralen (lime).