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

Abstract

AbstractThe 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. “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 tend to increase during the production season. 4′,5,6,7‐Tetramethoxyflavone (tetra‐O‐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‐O‐methylscutellarein levels are, on average, higher in the oils obtained from blond fruits than in the oils obtained from blood fruits. 3,3′,4′,5,6,7,8‐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.