190
9.1 Introduction
Seagrasses are marine angiosperms that colonize coastal and estuarine sediments
and play an important role in coastal food webs, carbon sequestration, sediment
stabilization and nutrient cycling (Orth et al. 1976). Seagrasses are amongst the
most productive aquatic autotrophic organisms on a global scale (Duarte and
Chiscano 1999). Zostera muelleri, commonly known as eel grass, is a marine flowering plant that forms extensive meadows in sheltered soft-bottom habitats along
North Atlantic and North Pacific temperate shores (Engle and Miller 2003).
Very few chemical and biological studies have been reported on Z. muelleri so
far; however Z. marina, a related species, has been well studied on chemical and
biological aspects. Pharmacological effects of Z. marina including antibiotic, antioxidant, nematicidal antimicrofoulant, antibacterial and anti-Labyrinthula properties have been reported (Kim et al. 2004; Custódio et al. 2016; Zidorn 2016). An
in vitro cytotoxic activity of Z. marina to selectively reduce the viability of tumorous neuronal cells has also been recently demonstrated (Custódio et al. 2016). The
most important constituent of Zostera spp. is zosteric acid, which is the most
intensely studied natural product from seagrasses, to which the antimicrofoulant
activity is attributed. Experimentally prepared silicone-based coatings containing
zosteric acid have proven to delay microfouling. Nematicidal and antibacterial
effects are attributed to rosmarinic acid (Achamlale et al. 2009). Other constituents
reported in Zostera spp. include apigenin-7-O-β-D-glucoside, chrysoeriol, gallic
acid, gentisic acid, p-hydroxybenzoic acid, vanillic acid, coumaric acid, caffeic acid
and ferulic acid (Kim et al. 2004, Zidorn 2016, Grignon-Dubois and Rezzonico
2012, Quackenbush et al. 1986, Kawasaki et al. 1998, De Leeuw et al. 1995). Even
though the presences of few other sulphated molecules have been reported, their
molecular structure is still unknown (Zidorn 2016).
Big ambiguity remains on the chemical diversity amongst seagrass taxa. Due to
the exposure of seagrasses to a number of unique environmental challenges, as well
as submersed lifestyle, a high diversity of defence chemicals are expected. A comprehensive investigation on the composition of Z. muelleri with the aid of new analytical techniques is lacking. Lack of metabolite information makes it difficult to
understand the pathways leading to the synthesis of secondary metabolites, their
enzymes and regulation by external stimuli or their roles in plant defence mechanism (Farag et al. 2012).
Chromatography coupled with mass spectrometry has become an indispensable
tool to elucidate the structure information without isolation and purification.
Metabolic profiling using these techniques can resolve individual chemical component into separate peaks, enhancing the opportunity to uncover novel or minor
9.3 Results and Discussion .................................................................................................... 193
9.3.1 Identification of Rosmarinic Acid and Zosteric Acid .......................................... 193
9.3.2 Profile of Z. muelleri ........................................................................................... 193
9.4 Conclusion ....................................................................................................................... 201
References ................................................................................................................................. 202
U. Kuzhiumparambil et al.
9.1 Introduction
Seagrasses are marine angiosperms that colonize coastal and estuarine sediments
and play an important role in coastal food webs, carbon sequestration, sediment
stabilization and nutrient cycling (Orth et al. 1976). Seagrasses are amongst the
most productive aquatic autotrophic organisms on a global scale (Duarte and
Chiscano 1999). Zostera muelleri, commonly known as eel grass, is a marine flowering plant that forms extensive meadows in sheltered soft-bottom habitats along
North Atlantic and North Pacific temperate shores (Engle and Miller 2003).
Very few chemical and biological studies have been reported on Z. muelleri so
far; however Z. marina, a related species, has been well studied on chemical and
biological aspects. Pharmacological effects of Z. marina including antibiotic, antioxidant, nematicidal antimicrofoulant, antibacterial and anti-Labyrinthula properties have been reported (Kim et al. 2004; Custódio et al. 2016; Zidorn 2016). An
in vitro cytotoxic activity of Z. marina to selectively reduce the viability of tumorous neuronal cells has also been recently demonstrated (Custódio et al. 2016). The
most important constituent of Zostera spp. is zosteric acid, which is the most
intensely studied natural product from seagrasses, to which the antimicrofoulant
activity is attributed. Experimentally prepared silicone-based coatings containing
zosteric acid have proven to delay microfouling. Nematicidal and antibacterial
effects are attributed to rosmarinic acid (Achamlale et al. 2009). Other constituents
reported in Zostera spp. include apigenin-7-O-β-D-glucoside, chrysoeriol, gallic
acid, gentisic acid, p-hydroxybenzoic acid, vanillic acid, coumaric acid, caffeic acid
and ferulic acid (Kim et al. 2004, Zidorn 2016, Grignon-Dubois and Rezzonico
2012, Quackenbush et al. 1986, Kawasaki et al. 1998, De Leeuw et al. 1995). Even
though the presences of few other sulphated molecules have been reported, their
molecular structure is still unknown (Zidorn 2016).
Big ambiguity remains on the chemical diversity amongst seagrass taxa. Due to
the exposure of seagrasses to a number of unique environmental challenges, as well
as submersed lifestyle, a high diversity of defence chemicals are expected. A comprehensive investigation on the composition of Z. muelleri with the aid of new analytical techniques is lacking. Lack of metabolite information makes it difficult to
understand the pathways leading to the synthesis of secondary metabolites, their
enzymes and regulation by external stimuli or their roles in plant defence mechanism (Farag et al. 2012).
Chromatography coupled with mass spectrometry has become an indispensable
tool to elucidate the structure information without isolation and purification.
Metabolic profiling using these techniques can resolve individual chemical component into separate peaks, enhancing the opportunity to uncover novel or minor
9.3 Results and Discussion .................................................................................................... 193
9.3.1 Identification of Rosmarinic Acid and Zosteric Acid .......................................... 193
9.3.2 Profile of Z. muelleri ........................................................................................... 193
9.4 Conclusion ....................................................................................................................... 201
References ................................................................................................................................. 202
U. Kuzhiumparambil et al.