J. of Supercritical Fluids 95 (2014) 348–354 Contents lists available at ScienceDirect The Journal of Supercritical Fluids j o ur na l ho me page: www.elsevier.com/locate/supflu Response surface optimization of supercritical CO 2 extraction of -tocopherol from gel and skin of Aloe vera and almond leaves Fatemeh Bashipour, Seyyed M. Ghoreishi ∗ Department of Chemical Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran a r t i c l e i n f o Article history: Received 3 June 2014 Received in revised form 23 September 2014 Accepted 24 September 2014 Available online 2 October 2014 Keywords: Supercritical CO2 extraction -Tocopherol Aloe vera Almond leaves Response surface methodology a b s t r a c t Supercritical fluid extraction (SFE) was studied as an alternative technology in the pharmaceutical indus- try for the separation of -tocopherol from gel and skin of Aloe vera and almond leaves. The influence of operating conditions was investigated on the recovery of supercritical carbon dioxide (SC-CO 2 ) extraction of -tocopherol from three-year old Aloe vera (Aloe barbadensis Miller) leaf gel. The obtained results were compared with the conventional Soxhlet extraction. Response surface methodology (RSM) was applied to optimize effective variables on the extracted recovery of -tocopherol. The maximum -tocopherol recovery of 53.41% from Aloe vera gel was obtained with employing RSM predicted optimal operating conditions of 32 MPa, 45.91 ◦ C, 0.84 ml SC-CO 2 /min and 140 min for extraction. The -tocopherol extrac- tion yield for gel and skin of Aloe vera and almond leaves at these optimal operating conditions were obtained 1.53, 16.29 and 2.61 mg/100 g dry sample, respectively. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Aloe vera is a member of Liliaceae family. One of the greatest nutritional and therapeutic types of the Aloe vera is Aloe barbadensis Miller which is rich in antioxidants. The plant has elongated and pointed leaves. Each leaf of Aloe vera consists of three main parts: the inner clear gel of Aloe vera (AVG), the middle layer of latex and the green outer thick skin of Aloe vera (AVS). The AVG is the major part of the leaf by volume, appears to be clear and mucilaginous and the AVS is sometimes marked with white-colored flecks [1]. Hu et al. [2] showed that among two, three and four-year-old Aloe vera, three-year-old species has a higher antioxidant effect. The various vitamins (such as E, C, and A) and low fat and high fiber content exist in A. barbadensis Miller which have therapeutic and beneficial effects on humans [1]. Vitamin E is the natural most effective lipid soluble antioxidant, and it is protective against many diseases, such as cancer and car- diovascular diseases. The most common form of vitamin E present in nature is -tocopherol which is the extremely valuable com- pound because of the highest vitamin E activity and application of this important additive to all kind of food products, cosmetics and other uses. Some of the sources of -tocopherol which is not ∗ Corresponding author. Tel.: +98 31 33915604; fax: +98 031 33912677. E-mail address: ghoreshi@cc.iut.ac.ir (S.M. Ghoreishi). synthesized by the human body are vegetable oils, fruits, seeds, nuts, cereals, and products derived from them [3,4]. At present, new extraction methods are being replaced instead of classical approaches such as solvent extraction and vacuum distillation. One of the most prominent of new methods is SFE, specifically SC-CO 2 extraction. This technique has proved to be effective for applications in chemical, petrochemical, environmen- tal pharmaceutical and food processes because of particular CO 2 properties that are non-explosive, non-toxic, and available in high purity with low cost and no-solvent residues [3,5]. SFE is capable of conserving the antioxidant properties of the extracts and this point is very important in pharmaceutical and food industry [6]. As CO 2 has low critical temperature (30.9 ◦ C), it can also be used as supercritical fluid to extract thermally labile compounds such as tocopherols which are sensitive to heat, light and oxygen. In addition to, the control of the solvent power is possible to a high efficiency of extraction by pressure change beyond critical value of CO 2 (7.38 MPa). Therefore, the SC-CO 2 extraction is suitable for the food processing industry such as extraction of essential oils from various plant materials [6,7]. There are several reports in literature on the supercritical CO 2 extraction of tocopherols from natural materials. The Table 1 presents the tocopherols extraction yield from some natural sources by SC-CO 2 extraction and their optimal conditions of extraction. In this study, the main objectives were -tocopherol extrac- tion from three-year-old AVG by SC-CO 2 and conventional Soxhlet http://dx.doi.org/10.1016/j.supflu.2014.09.034 0896-8446/© 2014 Elsevier B.V. All rights reserved.