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.

Publication details, including instructions for authors and subscription information: ABSTRACT: Deterioration products and processes of sweet orange oil (Citrus sinensis L. Osbeck) were investigated on the basis of simulated aging conditions. For these experiments, we employed an aqueous acidic orange oil emulsion which was exposed to UV-light at room temperature for specified periods of time. Subsequent GUMS analysis revealed some relevant changes in the composition of the orange oil. The treatment caused a significant increase in several known compounds, such as carvone, isopulegol, isomers of carveol, the limonene and linalool oxides. On the other hand, other constituents, such as neral, geranial and citronellal, decreased. Moreover, we were also able to identify a number of newly formed secondary constituents. Among these were p-mentha-l&dien-4-01, a-cyclocitral, photocitral A, iso(iso)pulegol, carvonecamphor, menthone, isomenthone, isomers of p-mentha-l( 7),8-dien-2-01 and isopiperitenol.