Vetiveria zizanioides is a tufted, perennial and scented grass originating from India. Essential oil extracted from the roots of Vetiveria zizanioides (VZ) has been used in traditional medicine and perfumery as well as in other cosmetic and aromatherapy applications. Current methods for the extraction of oil from VZ are principally hydro-distillation, steam distillation and extraction with organic solvent. However, the first two methods have several drawbacks, such as break-down of thermally-labile components, hydration reactions of certain chemical constituents, the need for post-extraction processes to remove water and incomplete extraction of essential oils from plant materials. Extraction with organic solvent presents the major disadvantage with regard to the presence of solvent residues in extracts, which makes the process less ideal for essential oil extraction.

Supercritical fluid extraction from natural sources attracts noticeable interest because of the inherent properties of supercritical fluids. Extraction via supercritical fluids allows operation at moderate conditions thus preserving the integrity of thermally-labile components, and is capable of preserving organoleptic characteristics of plant extracts, moreover it overcomes the drawbacks of the presence of toxic residual solvent in the products. The fluid of choice is carbon dioxdie owning to its availability, mild critical conditions, low cost and lack of toxicity. In this study, the supercritical fluid extraction (SCFE) of essential oil from VZ using CO2 as an extraction medium was optimized. Response surface methodology with central composite design was employed to optimize the process; three independent operating parameters over 5 levels have been investigated in a dynamic extraction process; and the flow rate of the extracting medium was fixed. Yields (mass of essential oil/mass of dry matter) obtained by SCFE were compared with the ones obtained by hydro-distillation and extraction with hexane. Yields achieved from SCFE were up to five times higher than yields obtained by hydro-distillation and comparable to the yield produced by solvent extraction. Compared to hydrodistillation and extraction with hexane, SCFE presented the distinctive advantages of being operated at low temperature and producing products free from residual solvent. The high yields and purity of extracts makes SCFE an attractive process for the essential oil industry which is under pressure to produce “clean essential oil”.