Supercritical Fluid Extraction of Terpenoids and Steroids from Plants

Terpenoids and steroids constitute the largest known group of plant secondary metabolites. The different groups of terpenes are formed from isoprene (C5) units in enzymatic reactions. Head-to-tail condensation of isoprene units results in the formation of monoterpenes (C10), sesquiterpenes (C15), diterpenes (C20), sesterpenes (C25) and polyterpenes. Tail-to-tail coupling of C15 and C20 units leads to the precursors of triterpenes (C30) and carotenes (C40) [1]. Supercritical fluid extraction (SFE) processes have gained increasing interest in production of high-value plant extracts for pharmaceutical, cosmetic and food industries in recent years. A large number of books and review papers have been published [2-5]. There are several reviews of systems, for which high-pressure phaseequilibrium data have been published [6-8]. The comprehensive book of Stahl and coworkers [2] contains a systematic review about the SFE of terpenes. This chapter describes a recent period of supercritical fluid extraction of botanical feedstocks. The natural terpenoids are discussed subsequently. It is demonstrated that most plants contain a wide spectrum of biologically active compounds which can be dissolved or precipitated selectively. Some of the most important trends affecting the uses of SFE extracts are identified.