Distinct fatty acid profile of ten brown macroalgae

Revista Brasileira de Farmacognosia Brazilian Journal of Pharmacognosy 23(4): 608-613, Jul./Aug. 2013 Distinct fatty acid profile of ten brown macroalgae Graça Silva, Renato B. Pereira, Patrícia Valentão, Paula B. Andrade,* Carla Sousa Article Received 13 Mar 2013 Accepted 26 Jun 2013 Available online 2 Aug 2013 Keywords: brown macroalgae GC-MS polyunsaturated fatty acids ω-6/ω-3 ratio ISSN 0102-695X DOI: 10.1590/S0102-695X2013005000048 REQUIMTE/Laboratório de Farmacognosia, Departamento de Química, Faculdade de Farmácia, Universidade do Porto, Portugal. Abstract: It is widely accepted that the consumption of ω-3 polyunsaturated fatty acids has beneficial effects on human health. In this work, ten brown macroalgae species collected along the Portuguese west coast were studied for their fatty acids composition by GC-MS after alkaline hydrolysis and derivatization. The results of this survey showed that different macroalgae from the same region display distinct fatty acids profile. Concerning ω-3 polyunsaturated fatty acids, eicosapentaenoic acid was found in all but one species. Additionally, some species contained docosahexaenoic acid. Linoleic acid, an essential fatty acid of the ω-6 series, was present in all studied macroalgae. Fucus spiralis L. exhibited the highest amounts of monounsaturated fatty acids and of polyunsaturated fatty acids of the ω-3 and ω-6 series. The ω-6/ω-3 ratio in half of the studied species was lower than 1. This information reinforces the potential application of some brown macroalgae as dietary sources of polyunsaturated fatty acids. Introduction Seaweeds, including brown algae, produce polyunsaturated fatty acids (PUFA), especially long chain fatty acids of the ω-3 series (Colombo et al., 2006). These acids are of high importance for the nourishment of man (Li et al., 2002). The ingestion of ω-3 PUFA promotes the decrease of cardiovascular and inflammatory diseases (e.g. arthritis associated with inflammation) and additionally reduces the risk of cancer (Calder, 2006). The beneficial effects on preventing the mortality from heart diseases may be associated with the reduced concentration of triacylglycerol and the inhibition of platelet aggregation, together with a direct antiarrhythmic effect (Leaf & Kang, 1996; Harris et al., 1997). Some authors suggest that the reduction of dietary ω-6 PUFA and the increase in ω-3 by adults and new-borns can contribute not only to reduce cardiovascular disease, but also to improve mental health (Simopoulos et al., 2000). As so, in recent years the interest of fatty acids present in seaweed experienced a significant growth. There are 1500-2000 species of brown algae worldwide (van den Hoek et al., 1995). The genus Cladostephus, Sargassum, Padina, Fucus, Cystoseira, Halopteris, Saccorhiza and Stypocaulon are representative examples found in the Portuguese Atlantic coast. In previous studies ten brown macroalgae species, namely Cladostephus spongiosus (Hudson) C. Agardh, 608 Cystoseira nodicaulis (Withering) M. Roberts, Cystoseira tamariscifolia (Hudson) Papenfuss, Cystoseira usneoides (Linnaeus) M. Roberts, Fucus spiralis (Linnaeus), Halopteris filicina (Grateloup) Kützing, Padina pavonica (Linnaeus) Thivy, Saccorhiza polyschides (Lightfoot) Batters, Sargassum vulgare (J. V. Lamouroux) C. Agardh and Stypocaulon scoparium (Linnaeus) Kützing, were studied by our group for their proline, phloroglucinol, mannitol, sterols and phlorotannins contents (Andrade et al., 2013).This study also allowed the identification of eight fatty acids in the ethanolic extract used for metabolic profiling (Andrade et al., 2013). The major fatty acids of P. pavonica and S. scoparium have also been reported (Kanias et al, 1992). However, as far as we know, a deeper stydy of the fatty acids composition of most of the algae found in this reagion was never attempted. C. spongiosus and S. vulgare from a different origin, the meditrerranean Portuguese coast (Pereira et al., 2012), and two other species, P. pavonica from the Persian Gulf (Tabarsa et al., 2012) and S. polyschides from the ‘Ría de Arousa’, Coruña, Spain (Sánchez-Machado et al., 2004), have been studied for their fatty acids composition. The ten species considered herein were thoroughly studied by our group for their sterols and phlorotannins contents, and anti-inflammatory and antimicrobial effects have been demonstrated for the phlorotannins rich extracts (Lopes et al., 2011; 2012). In this work, fatty acids profile was performed Distinct fatty acid profile of ten brown macroalgae Graça Silva et al. by gas chromatography-mass spectrometry (GC-MS) after alkaline hydrolysis and derivatization to the respective fatty acids methyl esters (FAME). Materials and methods Standards and reagents All reagents and solvents were of analytical grade. Authentic standards for GC-MS analysis were obtained from Supelco (Bellefonte, PA, USA). Sampling Three-four individuals of each species were randomly collected in Peniche, west coast of Portugal (39°22'3"N; 9°22'26"W). Samples were collected in September 2008, with the exceptions of S. polyschides, collected in June 2008, and C. usneoides and C. nodicaulis, collected in November 2009. Identity was ascertained by Teresa Mouga, PhD (GIRM). Voucher specimens were deposited at Laboratório de Farmacognosia, Faculdade de Farmácia, Universidade do Porto (C. spong-010908; C. nodic-011109; C. tamar-010908; C. usneoi-011109; F. spir-010908; H. filic-010908; P. pavon-010908; S. polys-010608; S. vulg-010908; S. scopar-010908). After collection, samples were protected from heat, air and light exposure, washed with NaCl 3.5% (m/v) to remove epiphytes, and immediately frozen. Then samples were lyophilised in a Labconco 4.5 Freezone apparatus (Kansas City, MO, USA). The dried material was powdered (particle size <910 µm) and kept in the dark, in a desiccator, until fatty acids extraction. Fatty acids extraction and derivatization Fatty acids extraction was performed by the Folch method as previously described (Ribeiro et al., 2009), with slight modifications. Briefly, 0.25 g of the dried algae plus 200 μL of 1 g/L methanolic solution of methyl jasmonate (internal standard) were extracted with 150 mL of chloroform:methanol (2:1), with magnetic stirring at 500 rpm, for 10 min, at 40 °C. The extraction procedure was repeated five times and the resulting extracts were pooled and concentrated to dryness under reduced pressure (40 °C). The residue was dissolved in 1 mL of methanol and then hydrolysed with 1 mL of KOH methanolic solution (11 g/L), at 90 °C, for 10 min. The free fatty acids originally present and those resulting from the alkaline hydrolysis were derivatized with 1 mL of BF3 methanolic solution (10%), at 90 °C, for 10 min. FAME were purified with 2×6 mL of isooctane and anhydrous sodium sulphate was added to assure the total absence of water. The resulting extract was evaporated to dryness under a stream of nitrogen and dissolved in (...truncated)