The nonvolatile fractions of cold-pressed peel oils of Key and Persian lime as well as grapefruit were separated by high-speed countercurrent chromatography (HS-CCC). In addition to the isolation of the main coumarins, psoralens and polymethoxyflavones, a number of minor constituents were enriched and successfully characterized by GC-MS and HPLC-UV. 5,7,8-Trimethoxycoumarin and the cyclical acetals of oxypeucedanin hydrate with citral were determined as new nonvolatile trace constituents of lime oils and confirmed by NMR spectroscopy. The citral oxypeucedaninyl acetals were found particularly in Key lime oil type A, which as a result of the juice-oil contact, is exposed to acidic conditions during industrial processing. Some of the confirmed minor constituents, such as pabulenol, isooxypeucedanin, and oxypeucedanin methanolate in lime as well as auraptenol in grapefruit, may have been generated by hydrolysis-sensitive precursors during CCC separation or their respective industrial processing techniques.

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The germacrene composition of various citrus peel oils was investigated. Detection and quantification of the thermally sensitive germacrenes A and C was achieved by employing extremely gentle GC conditions with 100°C maximum in injector and GC-oven. Germacrene A was found in all analyzed citrus oils with values from trace level to 0.46% of the volatiles, depending on variety and provenance. Germacrene C was identified in the peel oils of bergamot, bitter orange, lime, Minneola, Ortanique tangor, pummelo, Sweetie, tangerine and Yuzu with values of O.Ol-O.ijY%. In this context, germacrene C always occurred accompanied by germacrene B. Germacrene D was present in all citrus peel oils, with the exception of lemon, whereas bicyclogermacrene was a constituent of all examined citrus oils, except for lime. Distilled lime oil as acidic steam distillate possesses a special position, as it contained only germacrene B.

The composition of sesquiterpene hydrocarbons of distilled lime oils of different geographic origin was analyzed in detail. Gas chromatography on capillary columns of varied polarity was employed for the optimal separation of the components in GC/MS. This led to the unambiguous identification of a number of sesquiterpenes. a-Santalene, a-amorphene, epi-P-santalene, P-sesquiphellandrene, 4(14),7(11)-selinadiene and (E)-a-bisabolene were confirmed as so far unknown constituents of distilled lime oil. 4,7(1l)-Selinadiene was isolated in NMR purity and unequivocally assigned within the sesquiterpene fraction. Key Word IndexC t t m aurantfoliu, Rutaceae, distilled lime oil, sesquiterpene hydrocarbon composition, 4,7(1l)-selinadiene.

The sesquiterpene hydrocarbon composition of cold‐pressed lime oils of the Key lime (type A and B) and the Persian lime varieties were investigated. α‐Santalene, γ‐curcumene, β‐selinene, β‐sesquiphellandrene and 7‐epi‐α‐selinene were confirmed as so far unknown trace constituents of cold‐pressed lime oils. The usage of unusually gentle GC conditions permitted the establishment of germacrenes A and C, both thermally and chemically sensitive compounds, as important constituents of cold‐pressed lime oil for the first time. This allowed to demonstrate that the germacrenes A, B, C and D make up ca 25% of the sesquiterpene fraction in expressed Key lime oil. Usage of conventional GC conditions largely lead to the destruction of these heat‐labile compounds, which may be of organoleptic importance. The employed detection method also allowed the identification of germacrene‐A in Chinese citronella oil. Copyright © 2000 John Wiley & Sons, Ltd.