Volatile secondary metabolites from Spilanthes americana obtained by simultaneous steam distillation-solvent extraction and supercritical fluid extraction

Abstract

Secondary volatile metabolites were isolated by simultaneous distillation-solvent extraction (SDE) and supercritical (CO 2) extraction (SFE) from flowers, leaves and stems of Spilanthes americana (Mutis) Hieron (Compositae). The extracts were analyzed by capillary gas chromatography using flame ionization, nitrogen-phosphorus (NPD) or mass spectrometric detection. Compounds were identified according to their Kováts indexes, mass spectra (EI, 70 eV), or by comparison with standard substances. The method of extraction (SDE, SFE) and the source of the plant material (flowers, stems, leaves) affected the composition of the extracts. SFE extracts from stems were rich (>40%) in sesquiterpenes (α- and ß-bisabolenes, caryophyllene and cadinenes), while those from leaves and flowers were abundant in nitrogenated (43 and 27%) and oxygenated (36 and 23%) compounds. N-(isobutyl)-2 E,6 Z,8 E-decatrienamide, N-(2-methylbutyl)-2 E,6 Z,8 E-decatrienamide, decatrienamide, N-(isobutyl)-6 Z,83-decadienamide and N-(2-phenelethyl)2- E,6 Z,-8 E-decatrienamide are examples of the nitrogenated compounds found. SDE extracts from stems, leaves, and flowers of S. americana contained sesquiterpene levels of 32, 28 and 20%, and a generally higher proportion of oxygenated compounds (28, 52 and 32%) and monoterpenes (27, 10 and 42%) than their SFE counterparts. Only trace-level contents of nitrogenated compounds were found using NPD in SDE extracts. Some heavy hydrocarbons (C n >20) originated from flower pigments and waxes were isolated by SFE but not by SDE. SFE was both selective and highly efficient in the isolation of sesquiterpenes, heavy hydrocarbons and nitrogenated compounds (amides).