Water soluble fractions of rose-scented geranium ( Pelargonium species) essential oil

Abstract

The essential oil of rose-scented geranium ( Pelargonium species, family: Geraniaceae) obtained through steam or water plus steam distillation of shoot biomass is extensively used in the fragrance industry and in aromatherapy. During distillation, a part of the essential oil becomes dissolved in the distillation water (hydrosol) and is lost as this hydrosol is discarded. In this investigation, hydrosol was shaken for 30 min with hexane (10:1 proportion) and the hexane was distilled to yield `secondary' or `recovered' essential oil. The chemical composition of secondary oil was compared with that of `primary' oil (obtained directly by distilling shoot biomass of the crop). Primary oil accounted for 93.0% and secondary oil 7.0% of the total oil yield (100.2 ml from 100 kg green shoot biomass). Fifty-two compounds making up 95.0–98.5% of the primary and the secondary oils were characterized through gas chromatography (GC) and gas chromatography–mass spectroscopy (GC–MS). Primary oil was richer in hydrocarbons (8.5–9.4%), citronellyl formate (6.2–7.5%), geranyl formate (4.1–4.7%), citronellyl propionate (1.0–1.2%), α-selinene (1.8–2.2%), citronellyl butyrate (1.4–1.7%), 10- epi-γ-eudesmol (4.9–5.5%) and geranyl tiglate (1.8–2.1%). Recovered oil was richer in organoleptically important oxygenated compounds (88.9–93.9%), commercial rhodinol fraction (74.3–81.2%), sabinene (0.4–6.2%), cis-linool oxide (furanoid) (0.7–1.2%), linalool (14.7–19.6%), α-terpineol (3.3–4.8%) and geraniol (21.3–38.4%). Blending of recovered oil with primary oil is recommended to enhance the olfactory value of the primary oil of rose-scented geranium. Distillation water stripped of essential oil through hexane extraction can be recycled for distilling the next batch of rose-scented geranium.