Comparative Chemical Composition of Steam-Distilled and Water-Soluble Essential Oils of South American Marigold (Tagetes minuta L.)

Abstract

Flowering shoot biomass of feld-grown South American marigold (Tagetes minuta L.) was hydrodistilled in Clevenger-type apparatus, steam-distilled in a feld distillation unit and the distillation water was collected. Chemical profles of hydrodistilled, steam-distilled and water-soluble (recovered from the distillation water of feld distillation unit employing hexane as the solvent) essential oils were analyzed by GC and GC/MS. The solubility of T. minuta oil in cold water at room temperature (30° C), in hot water (80° C) and the effciencies of hydrodistillation and hexane methods for isolating dissolved oil in water were studied under laboratory conditions. The solubility of the oil ranged from 0.11% in cold water to 0.15% in hot water. Hydrodistillation recovered 33.3–36.7% of dissolved oil in hot water and 55.0–60.0% of dissolved oil in cold water. Hexane extraction recovered 82.7–83.3% of dissolved oil in hot water and 90.0–90.5% of dissolved oil in cold water. Hydrodistilled and steam-distilled oils were richer in mono-and sesquiterpene hydrocarbons, while the water-soluble oil was richer in oxygenated monoterpenes (83.1–93.5%). Hydrodistilled and steam-distilled oils contained (Z)-β-ocimene (13.6–42.2%), dihydrotagetone + (E)-β-ocimene (14.8–30.3%), (Z)-tagetone (7.1–11.9%), (Z)-ocimenone (3.7–5.9%) and (E)-ocimenone (1.8–12.7%) as their major constituents. The main components of the water-soluble oil were: dihydrotagetone + (E)-β-ocimene (3.9–6.8%), (Z)-tagetone (6.2–7.9%), (E)-ocimenone (10.7–13.0%) and geraniol + linalyl acetate (47.5–52.0%).