0139–3006/$ 20.00 © 2014 Akadémiai Kiadó, Budapest Acta Alimentaria, Vol. 44 (2), pp. 229–234 (2015) DOI: 10.1556/AAlim.2014.0006 SYNTHETIC METHODS TO OBTAIN CONJUGATED LINOLEIC ACIDS (CLAS) BY CATALYSIS – A REVIEW R.V. SALAMON a *, É. VARGÁNÉ-VISI b , CS.D. ANDRÁS a , ZS. CSAPÓNÉ KISS b and J. CSAPÓ a, b a Department of Food Science, Sapientia – Hungarian University of Transylvania, RO-530104 Csíkszereda, Szabadság tér 1. Romania b Department of Chemistry and Biochemistry, Faculty of Animal Science, Kaposvár University, H-7400 Kaposvár, Guba S. u. 40. Hungary (Received: 19 February 2013; accepted: 14 August 2013) The addition of synthetic CLA is a possible way in order to compose foods enriched with conjugated linoleic acids (CLAs). The most environmental friendly methods for CLA synthesis are based on microbial biosynthesis. With homogeneous catalysis using organometallic catalysts (Ru and Rh complexes) high (approximately 80%) yields were obtained with high selectivity related to bioactive isomers. The heterogeneous catalysis has the advantage that at the end of the reaction there is no need for a supplementary separation operation or recycling of the catalyst. In heterogeneous process, the maximum yield may even be higher than 90% and the selectivity remains quite high as the reaction conditions are optimized. The substrates for obtaining CLAs are, in general, linoleic acid or alkyl linoleates and the catalysis is acidic. The yield and the selectivity depend on the strength and the type of acidic sites, as well as on the size distribution of the particles. Beside the existing catalytic methods, a photocatalytic process with UV and visible light irradiation with iodine promoter can be applied. Keywords: conjugated linoleic acid, CLA, homogeneous catalysis, heterogeneous catalysis, photocatalytic process Recently many new health-benefit effects of the conjugated linoleic acids (CLAs) were discovered. They decrease the body fat quantity and increase muscle mass, possess antiinflammatory and cancer preventive effects, exert beneficial effects on the skeletal system, act as immunostimulants, and decrease the probability of asthma occurrence (HA et al., 1989; PARIZA et al., 2001). Theoretically 56 isomers exist, however, few of them (cis(c)-9,trans(t)-11; t-10,c-12- and t-9,t-11 CLA) have been shown to have significant biologic activity. The bioactivity of the c-9,t-11 CLA isomer (Fig. 1) was discovered two decades ago (HA et al., 1989) and this isomer is predominant in the natural products used as foods. The main foods rich in CLA are milk, dairy products, meat and fat of the ruminants, as this isomer is produced by the bacteria of the rumen microflora. Nowadays, CLAs are obtained for industrial purpose from vegetable oils that are processed at high temperature (PHILIPPAERTS et al., 2011). The basic method in the industrial approach is the isomerisation of linoleic acid (LA) with basic catalysis by which the amounts of the two formed isomers (c-9,t-11 and t-10,c-12 CLA) are almost equal, and the yield is quite high. This synthetic method cannot be applied for the direct transformation of vegetable oils into CLA-rich triacylglycerols, because ester bonds of triacylglycerols hydrolyze to free fatty acids (or salts) and glycerol. * To whom correspondence should be addressed. Phone: +40744401448; fax: +40266314657; e-mail: salamonrozalia@sapientia.siculorum.ro