Original article Gamma-linolenic extraction from seed by SCF and several solvent systems Jose ´ Luis Guil-Guerrero,* Juan Carlos Lo ´pez-Martı´nez & Pablo Campra-Madrid A ´ rea de Tecnologı´a de Alimentos, Universidad de Almerı´a, 04120 Almerı´a, Espan˜a (Received 13 August 2006; Accepted in revised form 12 March 2007) Summary Several oil sources of gamma-linolenic acid (GLA) were extracted from their corresponding seeds using several extracting systems: A, supercritical fluid extraction (CO 2 -SFE); B, methanol ⁄ acetyl chloride ⁄ hexane (1:0.05:0.5, v ⁄ v ⁄ v); C, chloroform ⁄ methanol ⁄ water (1:2:0.8, v ⁄ v); D, hexane ⁄ diethyl ether (1:1.5, v ⁄ v); E, hexane ⁄ ethanol (96%) (1:0.9, v ⁄ v); F, hexane ⁄ ethanol (96%) (1:2.5, v ⁄ v); G, 1-butanol; H, ethanol (96%); I, ethanol (96%) ⁄ water (1:1, v ⁄ v); J, potassium hydroxide ⁄ ethanol (96%) (0.0223:1, p ⁄ v). It is noticeable that the total fatty acids extracted by the solvent system I was significantly lower than the amounts obtained by the other extracting systems (P < 0.05), while the highest GLA purity for the majority of the seeds was obtained by using the system J. Keywords Borago officinalis, Echium fastuosum, fatty acid methyl esters, gamma-linolenic acid, oil extraction, seed oil, supercritical fluid extraction. Introduction Gamma-linolenic acid (GLA, 18:3n-6) is the first inter- mediate in the bioconversion of linoleic acid (LA, 18:2n- 6) to arachidonic acid (ARA, 20:4n-6) by the enzyme D6-desaturase. Under some conditions, this enzymatic activity is depressed, causing n-6 essential fatty acid (EFA) deficiency, which is responsible for the aetiology of a broad range of diseases, such as atopic eczema, diabetic neuropathy, rheumatoid arthritis, and cardio- vascular, reproductive and autoimmune disorders. The GLA has proved its therapeutic value in the treatment of these and other diseases such as cancer, viral infection, osteoporosis and alcoholism (Horrobin, 1999). The GLA occurs in the seed oils of several plant families, and typical species (Gunstone, 1999) and new sources have been reported in recent works as raw materials to obtain GLA (Guil-Guerrero et al., 2000a, 2001a,b, 2003a). Usually, the GLA oils are extracted to use as starting material to concentrate and ⁄ or purify GLA or in the human nutrition as medicinal oils (Campra-Madrid & Guil-Guerrero, 2002; Guil-Guerr- ero et al., 2000b, 2003b). Supercritical fluid extraction (SFE) has been also investigated to extract GLA oils, by using carbon dioxide (CO 2 ) as solvent. SFE is a processing technique which makes use of highly compressed gases to extract agriculturally derived products, such as seed oils (Mendes et al., 2003). It has been shown that using CO 2 as the extraction gas a highly efficient extraction of oil from seeds could be achieved. SFE is a unitary mass transfer operation based on the use of fluids at temper- atures and pressures above their critical values (Mar- tinelli et al., 1991; Mendes et al., 2006). The favourable transport properties of fluids near their critical points allows deeper penetration into solid plant matrix and more efficient and faster extraction than with conven- tional organic solvents and solvent-free extracts can be obtained because of the high volatility of these solvents under ambient conditions (Mohamed & Mansoori, 2002; Kotnik et al., 2006). To date, this technique has been used to extract GLA oils from Borago officinalis seeds (Dauksas et al., 2002; Molero Go´mez and Martı´- nez De La Ossa, 2002), Oenothera paradoxa seeds (Gawdzik et al., 1998), Oenothera biennis seeds (Favati et al., 1991; Zizovic et al., 1998) and Cunninghamella echinulata fungal oil (Certik & Horenitzky, 1999). In the present study, several seed sources of GLA oils were extracted to compare the total fatty acids (FA) ⁄ GLA extraction. Solvent extraction was accom- plished with different mixtures of organic solvents as extracting systems, and CO 2 -SFE was also used. Materials and methods Seed oil extraction Mature seeds were collected from their natural habitats and from gardens in the case of Echium fastuosum. The *Correspondent: Fax: 34 950 015484; e-mail: jlguil@ual.es International Journal of Food Science and Technology 2008, 43, 1176–1180 1176 doi:10.1111/j.1365-2621.2007.01586.x Ó 2007 Institute of Food Science and Technology Trust Fund