The composition of the polymethoxylated flavone (PMF) fraction of the Italian sweet orange and mandarin essential oils, obtained by normal-phase HPLC, is reported. The results refer to the whole production season 1991/92; the oils have been extracted by the usual Italian technologies, viz. 'MC', 'Pelatrice' and 'Torchi'. 3,3' ,4' ,5,6,7,8-Heptamethoxyflavone, 3' ,4' ,5,6,7,8-hexamethoxyflavone (nobiletin), 3,3' ,4' ,5,6,7-hexamethoxyflavone and 3',4',5,6,7-pentamethoxyflavone (sinensetin), in the sweet orange essential oil tend to increase during the production season. 4',5,6,7-Tetramethoxyflavone (tetra-0-methylscutellarein) increases only for oils extracted by the 'FMC' technique which is the preferred technique for 'blood' fruit while the 4',5,6,7,8-pentamethoxyflavone (tangeretin) content decreases when the oils are obtained by the 'pelatrice' technique which is the preferred technique for 'blond' fruit. Tangeretin, nobiletin and tetra-0-methylscutellarein levels are, on average, higher in the oils obtained from blond fruits than in the oils obtained from blood fruits. 3,3',4',5,6,7,& Heptamethoxyflavone and 3,3',4',5,6,7-hexamethoxyflavone show the opposite behaviour; for sinensetin there are no differences between 'pelatrice' and 'FMC' extracted oils.Mandarin essential oils produced with 'Pelatrice' extractors show a polymethoxyflavone content higher than oils produced with 'Torchi' extractors, while there are no quantitative differences between oils produced in different periods of the productive season.Standards for quantitative analysis have been isolated from sweet orange and mandarin oils by chromatography on silica gel columns and semi-preparative HPLC with recycling.

The content of bergamottin, 5-geranyloxy-7-methoxycoumarin, citropten and bergapten in Calabrian bergamot essential oil was determined by HPLC. 128 genuine bergamot essential oils, cold-pressed during the year 1992, were analysed; for each sample the date and area of production of the fruits is known.The percentage of bergamottin ranges between 1.02% and 2.75%. 5-geranyloxy-7-methoxycoumarin between 0.08 and 0.22%, citropten between 0.14% and 0.35%, bergapten between 0.11 YO and 0.32%. The mean content of bergamottin and 5-geranyloxy-7-methoxycoumarin did not vary during the production period, while that of citropten and bergapten decreased considerably from January to March. There does not seem to be any evident correlation between the production areas of the fruits and the coumarin composition. The presence of some peaks absent in genuine bergamot essential oils, has been detected in three bergamot oils, available on the market, probably because of lime oil addition.

Enantiomeric ratios of linalol in Italian sweet orange oils, Italian and foreign bitter orange oils, Uruguayan mandarin oils and mixtures of sweet and bitter orange oils are reported. A fully automatic on-line HPLC-HRGC system which allows the detection of the enantiomeric ratio without interference was used.The results are useful to distinguish bitter orange from sweet orange oils and European (Spain and Italy) from Brazilian and Ivory Coast bitter orange oils; moreover these results give information about the cultivars of mandarin and sweet orange oils from which they have been extracted.

The composition of the volatile fraction of Italian bitter orange essential oil, camed out by LC, HRGC and GC-MS, is reported: 60 components have been identified. The results obtained are compared with those in the literature for Italian and Spanish bitter orange oils.Two methods are suggested which allows the detection of contamination or possible additions of terpenes and oils of sweet orange and of lemon to genuine bitter orange oil. One is based upon the content of 6-3-carene and the value of the ratios 6-3-carenelcamphene and 6-3-carenelterpinolene which permits the detection of the additions of 5% of sweet orange terpenes and oils; the second is based upon the content of a-terpinene and the value of the ratios a-terpinenelcamphene and a-terpinenelcis-B-ocimene and allows the detection of the addition of even 3% of lemon terpenes and oils.

A rapid method for the detection of the addition of reconstituted bergamot oils to natural bergamot essential oils is suggested. The method is based on the ratio of the two enantiomers of linalol determined by gas chromatography with chiral capillary columns.