Polyunsaturated fatty acids in various macroalgal species from north Atlantic and tropical seas

van Ginneken et al. Lipids in Health and Disease 2011, 10:104 http://www.lipidworld.com/content/10/1/104 RESEARCH Open Access Polyunsaturated fatty acids in various macroalgal species from north Atlantic and tropical seas Vincent JT van Ginneken1†, Johannes PFG Helsper2*†, Willem de Visser1, Herman van Keulen1 and Willem A Brandenburg1 Abstract Background: In this study the efficacy of using marine macroalgae as a source for polyunsaturated fatty acids, which are associated with the prevention of inflammation, cardiovascular diseases and mental disorders, was investigated. Methods: The fatty acid (FA) composition in lipids from seven sea weed species from the North Sea (Ulva lactuca, Chondrus crispus, Laminaria hyperborea, Fucus serratus, Undaria pinnatifida, Palmaria palmata, Ascophyllum nodosum) and two from tropical seas (Caulerpa taxifolia, Sargassum natans) was determined using GCMS. Four independent replicates were taken from each seaweed species. Results: Omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acids (PUFAs), were in the concentration range of 2-14 mg/g dry matter (DM), while total lipid content ranged from 7-45 mg/g DM. The n-9 FAs of the selected seaweeds accounted for 3%-56% of total FAs, n-6 FAs for 3%-32% and n-3 FAs for 8%-63%. Red and brown seaweeds contain arachidonic (C20:4, n-6) and/or eicosapentaenoic acids (EPA, C20:5, n-3), the latter being an important “fish” FA, as major PUFAs while in green seaweeds these values are low and mainly C16 FAs were found. A unique observation is the presence of another typical “fish” fatty acid, docosahexaenoic acid (DHA, C22:6, n-3) at ≈ 1 mg/g DM in S. natans. The n-6: n-3 ratio is in the range of 0.05-2.75 and in most cases below 1.0. Environmental effects on lipid-bound FA composition in seaweed species are discussed. Conclusion: Marine macroalgae form a good, durable and virtually inexhaustible source for polyunsaturated fatty acids with an (n-6) FA: (n-3) FA ratio of about 1.0. This ratio is recommended by the World Health Organization to be less than 10 in order to prevent inflammatory, cardiovascular and nervous system disorders. Some marine macroalgal species, like P. palmata, contain high proportions of the “fish fatty acid” eicosapentaenoic acid (EPA, C20:5, n-3), while in S. natans also docosahexaenoic acid (DHA, C22:6, n-3) was detected. Background Polyunsaturated fatty acids (PUFAs) are essential nutrients which cannot, or only to a limited extent, be synthesised by mammals. Therefore, they must be ingested via dietary sources [1,2]. The two main PUFA classes are omega-3 (n-3) and omega-6 (n-6). The n-3 PUFAs are provided by fish and plant sources, whereas the n-6 PUFAs are ingested mainly via vegetable oil [2,3]. Degenerative diseases related to inappropriate fatty acid consumption form a major, potential death cause * Correspondence: † Contributed equally 2 Plant Research International, Business Unit Bioscience, P.O. Box 619, 6700 AP Wageningen, The Netherlands Full list of author information is available at the end of the article for two thirds of the population living in affluent, industrialised nations [4]. Sixty eight percent of the people die from three conditions which involve fatty acid (FA) degeneration: cardiovascular disease (43.8%), cancer (22.4%), and diabetes (1.8%) [5,6]. Two PUFAs which cannot be synthesized by humans and other vertebrates are linoleic acid (C18:2, n-6) and alinolenic acid (C18:3, n-3). The PUFAs include two metabolic series of compounds: the n-6 and the n-3 FAs. Linoleic acid belongs to the n-6 series while linolenic acid refers to both a-linolenic (C18:3, n-3) and g-linolenic acid (C18:3, n-6). Within the body both can be converted to other PUFAs such as arachidonic acid (C20:4, n-6), eicosapentaenoic acid (EPA, C20:5, n-3) and docosahexaenoic acid (DHA, C22:6, n-3). There are two pathways for the © 2011 van Ginneken et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. van Ginneken et al. Lipids in Health and Disease 2011, 10:104 http://www.lipidworld.com/content/10/1/104 conversion of C18 PUFAs to long chain PUFAs: Linoleic acid is converted to arachidonic acid in the n-6 series and a-linolenic acid is converted to EPA and DHA in the n-3 series (Figure 1, reviewed [3,7]). It is important to maintain an appropriate balance of n-3 and n-6 in the diet as these FAs work together to promote health: n-3 FAs have been recognised to exhibit anti-inflammatory and antioxidant activity, which may contribute to their beneficial cardiac effects [3,8,9], but also to the prevention of breast cancer [10]. In contrast, most n-6 FAs (precursors of arachidonic acid and prostaglandin E2) tend to promote inflammation and tumour growth [11,12]. Recently, it became clear that besides prevention of cardiovascular diseases [9,13,14] some n-3 PUFAs, especially EPA and DHA, are major components of brain cells and crucial for proper development and functioning of the brain and the nervous system [15,16]. Also with a world-wide increase in lifetime expectancy [17] it is an important observation that dietary n-3 fatty acid supplementation to the elderly results in an increased muscle protein synthesis, in this way preventing sarcopenic obesity [18]. Page 2 of 8 Until now the major source of n-3 and n-6 long-chain PUFAs, such as arachidonic acid, EPA and DHA, is fish oil [19]. However, it is noteworthy that the original source of these long-chain PUFAs is not the fish itself, but marine algae and phytoplankton which form their major dietary source [20]. A recent study [21,22] predicts a rapid worldwide depletion of fish populations. Already 29% of edible fish and seafood species has declined by 90%, which indicates a collapse of fisheries and salt-water fish extinction by the year 2048 [22]. Therefore, other sources for n-3 and n-6 FAs have to be found. Seaweeds are abundant and poorly exploited. Three major groups of seaweeds can be distinguished: Chlorophyta (1200 species), Phaeophyceae (2000 species) and Rhodophyta (6000 species) [23]. Although in general their lipid content is low we hypothesise that n-3 and n-6 PUFAs can be extracted from these macroalgae. In addition, the n-6: n-3 ratio, which is currently recommended by the WHO [24] to be lower than 10 in the diet, can possibly be improved by addition of certain edible seaweeds because of their high n-3 content. Methods Seaweeds Figure 1 Biosynthetic pathway for the dietary most important long-chain n-6 and n-3 polyunsaturated fatty acids. Fronds of nine different species of benthic marine macrophytes (macroalgae) with different growth strategies and morphologies were collected from the upper and mid-littoral zone in September and October 2009. Four replicates (...truncated)