60
cyclopenta(α)phenanthrene structure and a side chain at C17 (please refer to
Kumari et al. 2013a for detailed description of seaweed sterols structures and
occurrences). Seaweed sterols are extremely diverse with both the mevalonate
(MVA) and methyl-D- erythritol-4-phosphate (MEP) pathways of isoprenoid biosynthesis existing in seaweeds. Cholesterol is the dominant sterol in red seaweeds
and fucosterol in brown seaweeds, while the dominant sterol seems to vary within
the orders in green seaweeds (Al Easa et al. 1995) such as isofucosterol in Ulvales
and clionasterol in Bryopsidales and Siphonocladales. These seaweed sterols also
possess beneficial health-promoting effects such as hypercholesterolemic, antioxidant, anticancer, antidiabetic, antihypertensive, and anti-inflammatory responses
(Kim and Ta 2011 and references therein).
4.3 Seaweed Lipidomics: An Update
Seaweeds have been studied for decades for their health-benefitting and bioactive lipids. Multiple approaches have been employed for the separation, quantification, and
characterization of lipids including thin-layer chromatography (TLC), gas chromatography (GC), gas chromatography mass spectrometry (GC-MS), nuclear magnetic
resonance (NMR), liquid chromatography (LC) or high-pressure liquid chromatography (HPLC), and mass spectrometry with or without conjunction of a variety of complementary procedures such as chemical hydrolysis, regiospecific enzymatic cleavage,
and spectrophotometric assays mainly to unravel the lipid diversity in seaweeds, specifically fatty acids, oxylipins, and sterols, and to quantitate their abundance or for
their isolation and structural characterization. However, no method has yet been
developed that can decipher the complete lipidome. Recently, Kumari et al. (2015)
elucidated the first polar lipidome of Gracilaria dura under methyl jasmonate stress;
Melo et al. (2015) revealed whole polar lipidome of C. crispus and Chen et al. (2016)
of Pyropia haitanensis under high-temperature stress (discussed in detail in latter section). Moreover, “lipidomics” is relatively a new avenue in seaweed lipid research as
compared to microalgae where the impetus of biodiesel production has driven the
development of lipidomic field faster leading to the elucidation of lipid biosynthetic
pathways and the advancement in lipid and FA extraction techniques, strategies to
manipulate lipid metabolic pathways to obtain higher yields of lipid and FAs.
Numerous desaturases and elongases have been cloned and characterized from microalgae, which are extensively and timely reviewed by Harwood and Guschina (2009),
Khozin-Goldberg and Zvi (2011), and Khozin-Goldberg (2016). On contrary, our
knowledge on metabolic pathways of lipid and FA metabolism of seaweeds and the
genes involved is mainly based on those of higher plants and microalgae, and is
believed to be similar to them in one or more aspects. Recently, Chan et al. (2012)
identified the enzymes involved in FA biosynthesis such as acetyl CoA carboxylase,
FAS I/II, desaturases, and elongases and studied the FA desaturation patterns in transcriptomes of Pyropia spp. These authors identified all the four genes encoding the
P. Kumari
cyclopenta(α)phenanthrene structure and a side chain at C17 (please refer to
Kumari et al. 2013a for detailed description of seaweed sterols structures and
occurrences). Seaweed sterols are extremely diverse with both the mevalonate
(MVA) and methyl-D- erythritol-4-phosphate (MEP) pathways of isoprenoid biosynthesis existing in seaweeds. Cholesterol is the dominant sterol in red seaweeds
and fucosterol in brown seaweeds, while the dominant sterol seems to vary within
the orders in green seaweeds (Al Easa et al. 1995) such as isofucosterol in Ulvales
and clionasterol in Bryopsidales and Siphonocladales. These seaweed sterols also
possess beneficial health-promoting effects such as hypercholesterolemic, antioxidant, anticancer, antidiabetic, antihypertensive, and anti-inflammatory responses
(Kim and Ta 2011 and references therein).
4.3 Seaweed Lipidomics: An Update
Seaweeds have been studied for decades for their health-benefitting and bioactive lipids. Multiple approaches have been employed for the separation, quantification, and
characterization of lipids including thin-layer chromatography (TLC), gas chromatography (GC), gas chromatography mass spectrometry (GC-MS), nuclear magnetic
resonance (NMR), liquid chromatography (LC) or high-pressure liquid chromatography (HPLC), and mass spectrometry with or without conjunction of a variety of complementary procedures such as chemical hydrolysis, regiospecific enzymatic cleavage,
and spectrophotometric assays mainly to unravel the lipid diversity in seaweeds, specifically fatty acids, oxylipins, and sterols, and to quantitate their abundance or for
their isolation and structural characterization. However, no method has yet been
developed that can decipher the complete lipidome. Recently, Kumari et al. (2015)
elucidated the first polar lipidome of Gracilaria dura under methyl jasmonate stress;
Melo et al. (2015) revealed whole polar lipidome of C. crispus and Chen et al. (2016)
of Pyropia haitanensis under high-temperature stress (discussed in detail in latter section). Moreover, “lipidomics” is relatively a new avenue in seaweed lipid research as
compared to microalgae where the impetus of biodiesel production has driven the
development of lipidomic field faster leading to the elucidation of lipid biosynthetic
pathways and the advancement in lipid and FA extraction techniques, strategies to
manipulate lipid metabolic pathways to obtain higher yields of lipid and FAs.
Numerous desaturases and elongases have been cloned and characterized from microalgae, which are extensively and timely reviewed by Harwood and Guschina (2009),
Khozin-Goldberg and Zvi (2011), and Khozin-Goldberg (2016). On contrary, our
knowledge on metabolic pathways of lipid and FA metabolism of seaweeds and the
genes involved is mainly based on those of higher plants and microalgae, and is
believed to be similar to them in one or more aspects. Recently, Chan et al. (2012)
identified the enzymes involved in FA biosynthesis such as acetyl CoA carboxylase,
FAS I/II, desaturases, and elongases and studied the FA desaturation patterns in transcriptomes of Pyropia spp. These authors identified all the four genes encoding the
P. Kumari