On the genuineness of citrus essential oils. Part XLVI. Polymethoxylated flavones of the non-volatile residue of Italian sweet orange and mandarin essential oils

Dugo, P.; Mondello, L.; Cogliandro, E.; Stagno d' Alcontres, I.; Cotroneo, A.

Flavour and Fragrance Journal 9(3): 105-111

1994


ISSN/ISBN: 0882-5734
DOI: 10.1002/ffj.2730090304
Accession: 002665063

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Abstract
In Italy, sweet orange essential oils are obtained from various cultivars of blond oranges (early, Dec.-Feb., and late, after Apr.) and blood oranges (mainly in mid-season, Feb.-Apr.). The mandarin season begins in Oct.-Nov. with unripe fruits; partly ripe fruits are extracted in Dec. and fully-ripe (red) fruits in Jan.-Feb. The composition of the polymethoxylated flavone (PMF) fraction of the 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 were extracted by the usual Italian technologies, viz. FMC, 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 tended to increase during the production season. 4',5,6,7-Tetramethoxyflavone (tetra-O-methylscutellarein) increased only for oils extracted by the FMC technique (preferred for blood fruits), while the 4',5,6,7,8-pentamethoxyflavone (tangeretin) content decreased when the oils were obtained by the Pelatrice technique (preferred for blond fruits). Tangeretin, nobiletin and tetra-O-methylscutellarein levels were on average, higher in the oils obtained from blond fruits than in those from blood fruits. 3,3',4',5,6,7,8-Heptamethoxyflavone and 3,3',4',5,6,7-hexamethoxyflavone showed the opposite behaviour; for sinensetin there were no differences between Pelatrice and FMC extracted oils. Mandarin essential oils produced with Pelatrice extractors had a higher polymethoxyflavone content than oils produced with Torchi extractors, while there were no quantitative differences between oils produced in different periods of the productive season. Standards for quantitative analysis were isolated from both groups of oils by chromatography on silica gel columns, and semi-preparative HPLC with recycling.

On the genuineness of citrus essential oils. Part XLVI. Polymethoxylated flavones of the non-volatile residue of Italian sweet orange and mandarin essential oils