57
position of the first double bond from the methyl end. Seaweeds have been extensively explored for their fatty acids, especially PUFAs (representing10–70% of total
fatty acids; TFAs) due to their chemotaxonomic and nutritional importance, with
their compositions varying even within the same phyla (Galloway et al. 2012;
Khotimchenko et al. 2002; Kumari et al. 2010; Kumari et al. 2013b; Li et al. 2002).
The characteristic chemotaxonomic biomarkers are established in seaweeds, with
green seaweeds containing higher contents of C18 PUFAs (ALA, STA, and LA),
red seaweeds containing C20 PUFAs (AA and EPA), and brown seaweeds containing both C18 and C20 PUFAs in appreciable amounts. These long-chain PUFAs,
particularly n-3 PUFAs (ALA, STA, and EPA) which cannot be synthesized by
humans and thus obtained through diet, are indispensable for proper growth and
development of organisms, prevention of cardiovascular and other chronic diseases
such as diabetes, hypertension, and autoimmune diseases, and DHA for visual and
neurological health, while AA and EPA are precursors of bioregulators prostaglandins, thromboxanes, and other eicosanoids, which influence inflammation processes
and immune reactions (Calder and Grimble 2002).
4.2.6.2 Oxylipins
Oxylipins are lipid signaling oxygenated derivatives of PUFAs formed enzymatically
either by lipoxygenases (LOX) or α-dioxygenases (α-DOX) or by chemical (auto)
oxidation that mediates intra- and intercellular processes such as development, inflammation, and stress responses. These compounds are widely distributed in seaweeds
with considerable species-specific differences due to the variability of both FAs and
enzymatic transformations. Seaweeds possess both plant- and animal- type oxylipins,
i.e., octadecanoid and eicosanoid pathways emanating from C18 and C20 PUFAs,
respectively, as well as docosanoid pathway emanating from C22PUFAs, recently
reviewed by Kumari et al. (2013a, 2014a) and Barbosa et al. (2016). C18 PUFAs are
metabolized either at C-9 or C-13 via 9- and 13-LOX, respectively; C20 PUFAs are
transformed at C-5, C-8, C-9, C-11, C-12, and C-15 via 5-, 8-, 9-, 11-, 12-, and
15-LOX, respectively; and C22 PUFAs are mainly transformed at C-14 by 14-LOX,
forming their respective hydroperoxides (Barbosa et al. 2016 and Kumari et al. 2013a,
b for detailed structures and occurrence of seaweed oxylipins). Further, these hydroperoxides are transformed into hydroxy-, oxo-, and epoxy-fatty acids and polyunsaturated aldehydes (PUAs) by the action of peroxidases, oxygenases, epoxygenases, and
hydroperoxide lyases (HPL), respectively (Figs. 4.2 and 4.3) (Andreou and Feussner
2009; Bouarab et al. 2004; Gerwick et al. 1993; Kumari et al. 2014a; Lion et al. 2006;
Ritter et al. 2008, 2014). Moreover, some red algae also form prostaglandins and leukotrienes either nonenzymatically or by the enzymatic action of allele oxide synthase/
cyclase (AOS/AOC) or cyclooxygenase (COX) analogous to animals (Andreou and
Feussner 2009). Recently, Kanamoto et al. (2011) identified COX gene in Gracilaria
vermiculophylla (Ohni) Papenfuss and cloned it in Escherichia coli for the production
of PGF 2α . Apart from these simple oxylipins, macroalgae also contain various
4 Seaweed Lipidomics in the Era of ‘Omics’ Biology: A Contemporary Perspective
position of the first double bond from the methyl end. Seaweeds have been extensively explored for their fatty acids, especially PUFAs (representing10–70% of total
fatty acids; TFAs) due to their chemotaxonomic and nutritional importance, with
their compositions varying even within the same phyla (Galloway et al. 2012;
Khotimchenko et al. 2002; Kumari et al. 2010; Kumari et al. 2013b; Li et al. 2002).
The characteristic chemotaxonomic biomarkers are established in seaweeds, with
green seaweeds containing higher contents of C18 PUFAs (ALA, STA, and LA),
red seaweeds containing C20 PUFAs (AA and EPA), and brown seaweeds containing both C18 and C20 PUFAs in appreciable amounts. These long-chain PUFAs,
particularly n-3 PUFAs (ALA, STA, and EPA) which cannot be synthesized by
humans and thus obtained through diet, are indispensable for proper growth and
development of organisms, prevention of cardiovascular and other chronic diseases
such as diabetes, hypertension, and autoimmune diseases, and DHA for visual and
neurological health, while AA and EPA are precursors of bioregulators prostaglandins, thromboxanes, and other eicosanoids, which influence inflammation processes
and immune reactions (Calder and Grimble 2002).
4.2.6.2 Oxylipins
Oxylipins are lipid signaling oxygenated derivatives of PUFAs formed enzymatically
either by lipoxygenases (LOX) or α-dioxygenases (α-DOX) or by chemical (auto)
oxidation that mediates intra- and intercellular processes such as development, inflammation, and stress responses. These compounds are widely distributed in seaweeds
with considerable species-specific differences due to the variability of both FAs and
enzymatic transformations. Seaweeds possess both plant- and animal- type oxylipins,
i.e., octadecanoid and eicosanoid pathways emanating from C18 and C20 PUFAs,
respectively, as well as docosanoid pathway emanating from C22PUFAs, recently
reviewed by Kumari et al. (2013a, 2014a) and Barbosa et al. (2016). C18 PUFAs are
metabolized either at C-9 or C-13 via 9- and 13-LOX, respectively; C20 PUFAs are
transformed at C-5, C-8, C-9, C-11, C-12, and C-15 via 5-, 8-, 9-, 11-, 12-, and
15-LOX, respectively; and C22 PUFAs are mainly transformed at C-14 by 14-LOX,
forming their respective hydroperoxides (Barbosa et al. 2016 and Kumari et al. 2013a,
b for detailed structures and occurrence of seaweed oxylipins). Further, these hydroperoxides are transformed into hydroxy-, oxo-, and epoxy-fatty acids and polyunsaturated aldehydes (PUAs) by the action of peroxidases, oxygenases, epoxygenases, and
hydroperoxide lyases (HPL), respectively (Figs. 4.2 and 4.3) (Andreou and Feussner
2009; Bouarab et al. 2004; Gerwick et al. 1993; Kumari et al. 2014a; Lion et al. 2006;
Ritter et al. 2008, 2014). Moreover, some red algae also form prostaglandins and leukotrienes either nonenzymatically or by the enzymatic action of allele oxide synthase/
cyclase (AOS/AOC) or cyclooxygenase (COX) analogous to animals (Andreou and
Feussner 2009). Recently, Kanamoto et al. (2011) identified COX gene in Gracilaria
vermiculophylla (Ohni) Papenfuss and cloned it in Escherichia coli for the production
of PGF 2α . Apart from these simple oxylipins, macroalgae also contain various
4 Seaweed Lipidomics in the Era of ‘Omics’ Biology: A Contemporary Perspective