199
metabolites wherein some have focused on their bioactive potential (Papenbrock
2012; Subhashini et al. 2013). However, considering almost 72 species of seagrasses
distributed across the globe, only few have been examined for natural bioactives and
their associated role. So far, seagrass Posidonia oceanica is the only most studied
species with the identification of almost 51 natural compounds belonging to phenols, phenyl-methane/ethane/propane and their derivatives and flavonoids (Zidorn
2016; Subhashini et al. 2013). These secondary metabolites have been suggested to
play crucial role not only for growth and development but also in defence from
environmental stress, pathogen attack and herbivory (Kumar et al. 2016).
The importance of primary polar metabolites (such as sugars, TCA intermediates, amino acids, and/or polyalcohols) as taxonomical and physiological traits has
also been well reported. In this study, 24 amino acids and 16 compounds related to
“sugar and derivatives” were detected (Tables 9.1 and 9.2). Sugars, amino acids and
organic acids are the major energy sources for photosynthesis and respiration in
plants. Sugars, as a carbon source, provide the energy required for growth and
development, and amino acids, as a nitrogen source, promote rapid growth.
In recent years, the role of primary metabolites in stress physiology of seagrasses
has been reported. A metabolomic study on diurnal effects of anoxia in Z. marina
identified varied expression levels of lactate, pyruvate, GABA (γ-aminobutyric
acid), succinate, alanine, glutamate and glutamine. It was suggested that the function of the alanine-GABA shunt was to mitigate the toxic effects of lactate or ethanol produced during anoxic condition, by providing an alternative route for pyruvate
metabolism. Also, alanine and GABA accumulation together with glutamate and
glutamine allowed carbon and nitrogen storage during anoxia, and this would provide energy for metabolism upon re-establishment of normoxic conditions (HaslerSheetal et al. 2015). Another study on adaptive mechanism for chronic heat stress in
Z. marina and Z. noltii have identified sucrose, fructose and myo-inositol as the
most responsive metabolites (Gu et al. 2012). Given the osmoprotective function of
sugars, the accumulation of myo-inositol in both species was suggested to act as a
substrate to generate protein-stabilizing osmolytes such as di-myo-inositol phosphate. Further, differential expression of primary metabolites, particularly sugars
such as glucose and fructose, has been reported in Z. marina under light stress conditions (Hasler-Sheetal et al. 2016). Therefore, identification of these metabolites
and studying their regulation under stressful environment can provide insights on
the acclimation and/or tolerance mechanism of Z. muelleri (an abundant species of
Zosteraceae family in Australia) under the scenario of global climate change.
In both terrestrial and sea plants, shikimate pathway has been evident as the
major pathway for the synthesis of phenylpropanoid and flavonoid derivatives forming the bulk of metabolites (Zidorn 2016; Papenbrock 2012). In the present study,
phenolic acids such as caffeic, rosmarinic, zosteric and ferulic acid and
3- hydroxycoumarin were detected as major phenolic acids with homovanillic being
identified for the first time in Zostera species. The identified phenolics were either
hydroxybenzoic acid or hydroxycinnamic acid derivatives. An array of phenolic
compounds such as coumaric acid, caffeic acid, ferulic acid, vanillic acids and rosmarinic acid have also been reported from leaf samples of P. oceanica and Z. marina
9 Gas and Liquid Chromatography-Mass Spectrometry-Based Metabolic Profiling…
metabolites wherein some have focused on their bioactive potential (Papenbrock
2012; Subhashini et al. 2013). However, considering almost 72 species of seagrasses
distributed across the globe, only few have been examined for natural bioactives and
their associated role. So far, seagrass Posidonia oceanica is the only most studied
species with the identification of almost 51 natural compounds belonging to phenols, phenyl-methane/ethane/propane and their derivatives and flavonoids (Zidorn
2016; Subhashini et al. 2013). These secondary metabolites have been suggested to
play crucial role not only for growth and development but also in defence from
environmental stress, pathogen attack and herbivory (Kumar et al. 2016).
The importance of primary polar metabolites (such as sugars, TCA intermediates, amino acids, and/or polyalcohols) as taxonomical and physiological traits has
also been well reported. In this study, 24 amino acids and 16 compounds related to
“sugar and derivatives” were detected (Tables 9.1 and 9.2). Sugars, amino acids and
organic acids are the major energy sources for photosynthesis and respiration in
plants. Sugars, as a carbon source, provide the energy required for growth and
development, and amino acids, as a nitrogen source, promote rapid growth.
In recent years, the role of primary metabolites in stress physiology of seagrasses
has been reported. A metabolomic study on diurnal effects of anoxia in Z. marina
identified varied expression levels of lactate, pyruvate, GABA (γ-aminobutyric
acid), succinate, alanine, glutamate and glutamine. It was suggested that the function of the alanine-GABA shunt was to mitigate the toxic effects of lactate or ethanol produced during anoxic condition, by providing an alternative route for pyruvate
metabolism. Also, alanine and GABA accumulation together with glutamate and
glutamine allowed carbon and nitrogen storage during anoxia, and this would provide energy for metabolism upon re-establishment of normoxic conditions (HaslerSheetal et al. 2015). Another study on adaptive mechanism for chronic heat stress in
Z. marina and Z. noltii have identified sucrose, fructose and myo-inositol as the
most responsive metabolites (Gu et al. 2012). Given the osmoprotective function of
sugars, the accumulation of myo-inositol in both species was suggested to act as a
substrate to generate protein-stabilizing osmolytes such as di-myo-inositol phosphate. Further, differential expression of primary metabolites, particularly sugars
such as glucose and fructose, has been reported in Z. marina under light stress conditions (Hasler-Sheetal et al. 2016). Therefore, identification of these metabolites
and studying their regulation under stressful environment can provide insights on
the acclimation and/or tolerance mechanism of Z. muelleri (an abundant species of
Zosteraceae family in Australia) under the scenario of global climate change.
In both terrestrial and sea plants, shikimate pathway has been evident as the
major pathway for the synthesis of phenylpropanoid and flavonoid derivatives forming the bulk of metabolites (Zidorn 2016; Papenbrock 2012). In the present study,
phenolic acids such as caffeic, rosmarinic, zosteric and ferulic acid and
3- hydroxycoumarin were detected as major phenolic acids with homovanillic being
identified for the first time in Zostera species. The identified phenolics were either
hydroxybenzoic acid or hydroxycinnamic acid derivatives. An array of phenolic
compounds such as coumaric acid, caffeic acid, ferulic acid, vanillic acids and rosmarinic acid have also been reported from leaf samples of P. oceanica and Z. marina
9 Gas and Liquid Chromatography-Mass Spectrometry-Based Metabolic Profiling…