Glycerolipid Composition of the Red Macroalga Agarophyton Chilensis and Comparison to the Closely Related Agarophyton Vermiculophyllum Producing Different Types of Eicosanoids

Abstract

The red macroalga Agarophyton chilensis is a well-known producer of eicosanoids such as hydroxyeicosatetraenoic acids, but the alga produces almost no prostaglandins, unlike the closely related A. vermiculophyllum. This indicates that the related two algae would have different enzyme systems or substrate composition. To carry out more in-depth discussions on the metabolic pathway of eicosanoids between the two algae, we investigated the characteristics of glycerolipids, which are the substrates of eicosanoids production, of A. chilensis and compared them to the reported values of A. vermiculophyllum. In A. chilensis, monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol (SQDG), and phosphatidylcholine (PC) were the major lipid classes and accounted for 44.4% of the total lipid extract. The predominant fatty acids were arachidonic acid (20:4n-6), an eicosanoids precursor, and palmitic acid (16:0). The 20:4n-6 content was extremely high in MGDG and PC (>70%), and the 16:0 content was extremely high in DGDG and SQDG (>40%). A chiral-phase HPLC analysis showed that fatty acids were esterified at the sn-1 and sn-2 positions of those lipids. The glycerolipid molecular species were determined by reversed-phase HPLC–ESI–MS analysis. The main glycerolipid molecular species were 20:4n-6/20:4n-6 (sn-1/sn-2) for MGDG (63.8%) and PC (48.2%), 20:4n-6/16:0 for DGDG (71.1%) and SQDG (29.4%). These lipid characteristics of A. chilensis were almost the same as those of A. vermiculophyllum. Hence, the differences of the eicosanoids producing ability between the two algae would not be due to the difference of substrate composition but the difference of enzyme system.

Characterization of anAgarophyton chilenseoleoresin containing PPARγ natural ligands with insulin-sensitizing effects in a C57BL/6J mouse model of diet-induced obesity and antioxidant activityin Caenorhabditis elegans

“…In contrast, the total content of omega-6 fatty acids was higher (Table 1). ARA is the precursor of eicosanoids and oxylipins, bioactive lipidic promoters of the defense response in seaweed (19, 20). Most natural and endogenous PPARγ ligands are derived from ARA metabolization (84); therefore, the increased abundance in this seaweed extract may account for its high PPARγ transactivation capacity.…”

“…This interest is paralleled with an increase in the study of the biomedical potential of seaweed due to the large amounts of bioactive molecules they possess (11,90–92). The study of the lipid components of A. chilense and other closely related red seaweeds had demonstrated the presence of PUFAs and eicosanoids (19,22,37); however, whether the lipids present in the Agarophyton genus were able to activate PPARγ and had insulin sensitizer and antioxidant effects in vivo was unknown. Here, we demonstrated that A.chilense oleoresin includes ligands that are able to activate PPARγ with a similar level of activation to that observed with the partial PPARγ activators FMOC-Leu and INT131.…”

“…The authors also found that it was possible to promote oxylipin biosynthesis by subjecting the algal tissue to a mechanical damage. Physiologically, these oxylipins are produced after the release of ARA by phospholipase A and conversion by lipoxygenase as defense signals against epiphytes (19,20,22,24). Our procedure for obtaining Gracilex® included mechanical trituration of algae to activate its intrinsic defense mechanism and subsequent extraction with DCM, suggesting that this step may increase the oxylipin content of the extract.…”

“…Further studies will determine if this is the case in the future. A recent analysis of the A. chilensés lipids by Honda et al (19) revealed that glycerolipids comprise the largest proportion of the total lipid contents (monogalactosyldiacylglycerol and phosphatidylcholine), carrying mostly a combination of ARA and palmitic acids (20:4n-6/16:0) in their structure. In agreement with this study, our analysis of the fatty acid profile of Gracilex® showed that palmitic acid and ARA were the most abundant fatty acids, representing 40% and 21.1% of the total fatty acids, respectively.…”

“…Various methods of extraction are used to obtain enriched fractions derived from seaweeds containing antioxidant and pigment molecules (14, 15), proteins (16), polysaccharides (17) and lipids (18, 19). Particularly in the Gracilaria genus, lipid extractions obtained by classical chloroform:methanol mixtures have revealed a complex lipid composition of glycerolipids and omega-3 and omega-6 polyunsaturated fatty acids and their oxidized derivatives, known as oxylipins (18–21).…”