200
(Subhashini et al. 2013; Cuny et al. 1995; Haznedaroglu and Zeybek 2007). Zosteric
acid is the marker bioactive isolated from various Zostera species and was first discovered in Z. marina (Todd et al. 1993). Zosteric acid is a phenylpropane derivative
(p-(sulphoxy) cinnamic acid) with huge antifouling activities. Zosteric acid has
been documented to inhibit colonization of bacteria and fungus thus hinders their
biofilm formation and offers a zosteric acid as a promising broad spectrum antifoulant [hindering biofilm formation with zosteric acid]. Another major biomarker phenolic in Zostera species in rosmarinic acid identified in this study is caffeoyl ester,
which has diverse applications from food preservatives to cosmetics due to its high
antioxidant activity. Rosmarinic acid isolated from Z. marina and other species
exhibited nematicidal, antibacterial and algicidal activities (Wang et al. 2012; Laabir
et al. 2013). The identified phenolics in this study have been shown to exhibit antiLabyrinthula activity isolated from Z. marina as natural defence against this pathogen (Vergeer and Develi 1997). In seagrasses, phenolics have been shown to
accumulate considerably in most of the adverse conditions caused by environmental
stress such as high light and salinity fluctuations. In contrast, recently a noticeable
loss in phenolic substances (vanillin, coumaric and ferulic acid, proanthocyanidins)
has been observed in seagrass Cymodocea nodosa, Ruppia maritima and
Potamogeton perfoliatus with high grazing rate during ocean acidification conditions. These observations temper the recent predictions that seagrass would necessarily be “winners” in a high CO 2 world.
Flavonoids are another class of major metabolites identified in this study. In seagrasses, the polyphenolic flavonoids generally exist as flavones, flavonols, flavanons, flavanols and anthocyanidins and are synthesized from a common
precursor – phenylalanine. In the present study, the identified flavonoids include
flavonoid glycosides (luteolin 4'-glucoside and luteolin 5-(6''-malonylglucoside)),
sulphated flavonoids (luteolin 4'-sulphate, luteolin 4'-methyl ether 3'-sulfate and
apigenin 7-sulphate), flavone (luteolin and 5,2',5'-trihydroxyflavone) and flavanol
(kaempferide). Sulphated flavonoids are of particular interest due to its role in plant
physiology as a growth regulator and its ability to form stable complexes with other
flavonoids. They are also well known for various biological activities such as antiinflammatory, antiviral and antitumour activity (Subhashini et al. 2013). We reported
here for the first time the existence of luteolin 3′-methyl ether 7-sulphate in Z. muelleri; however, this requires further confirmatory analysis. Seagrasses Halophila,
Enhalus, Thalassia and Zostera species have been the most studied for the presence
of sulphated flavonoids, with no record of such flavonoids in Posidonia sp. A considerable accumulation of flavonoids such as luteolin 7-sulphate and luteolin
7,3′-disulphate has been observed in Z. marina as a strategy of chemical defence to
inhibit marine microorganism (Enerstvedt et al. 2016). In our study, luteolin 4′-glucoside and luteolin 5-(6″-malonylglucoside) are the only flavonoid glycosides that
we observed. The existence of luteolin 7-O-glucoside, diosmetin-7-O-glucoside (Z.
marina and Z. nana) and luteolin 7-O-glucoside (Z. noltii) suggests that Zostera
spp. are strong enough to synthesize these flavonoid derivatives in stressful aquatic
environment (Zidorn 2016; Subhashini et al. 2013). Similar to our findings, the
presence of malonylated flavone glycoside derivatives has also been observed in
Halophila stipulacea (Papenbrock 2012).
U. Kuzhiumparambil et al.
(Subhashini et al. 2013; Cuny et al. 1995; Haznedaroglu and Zeybek 2007). Zosteric
acid is the marker bioactive isolated from various Zostera species and was first discovered in Z. marina (Todd et al. 1993). Zosteric acid is a phenylpropane derivative
(p-(sulphoxy) cinnamic acid) with huge antifouling activities. Zosteric acid has
been documented to inhibit colonization of bacteria and fungus thus hinders their
biofilm formation and offers a zosteric acid as a promising broad spectrum antifoulant [hindering biofilm formation with zosteric acid]. Another major biomarker phenolic in Zostera species in rosmarinic acid identified in this study is caffeoyl ester,
which has diverse applications from food preservatives to cosmetics due to its high
antioxidant activity. Rosmarinic acid isolated from Z. marina and other species
exhibited nematicidal, antibacterial and algicidal activities (Wang et al. 2012; Laabir
et al. 2013). The identified phenolics in this study have been shown to exhibit antiLabyrinthula activity isolated from Z. marina as natural defence against this pathogen (Vergeer and Develi 1997). In seagrasses, phenolics have been shown to
accumulate considerably in most of the adverse conditions caused by environmental
stress such as high light and salinity fluctuations. In contrast, recently a noticeable
loss in phenolic substances (vanillin, coumaric and ferulic acid, proanthocyanidins)
has been observed in seagrass Cymodocea nodosa, Ruppia maritima and
Potamogeton perfoliatus with high grazing rate during ocean acidification conditions. These observations temper the recent predictions that seagrass would necessarily be “winners” in a high CO 2 world.
Flavonoids are another class of major metabolites identified in this study. In seagrasses, the polyphenolic flavonoids generally exist as flavones, flavonols, flavanons, flavanols and anthocyanidins and are synthesized from a common
precursor – phenylalanine. In the present study, the identified flavonoids include
flavonoid glycosides (luteolin 4'-glucoside and luteolin 5-(6''-malonylglucoside)),
sulphated flavonoids (luteolin 4'-sulphate, luteolin 4'-methyl ether 3'-sulfate and
apigenin 7-sulphate), flavone (luteolin and 5,2',5'-trihydroxyflavone) and flavanol
(kaempferide). Sulphated flavonoids are of particular interest due to its role in plant
physiology as a growth regulator and its ability to form stable complexes with other
flavonoids. They are also well known for various biological activities such as antiinflammatory, antiviral and antitumour activity (Subhashini et al. 2013). We reported
here for the first time the existence of luteolin 3′-methyl ether 7-sulphate in Z. muelleri; however, this requires further confirmatory analysis. Seagrasses Halophila,
Enhalus, Thalassia and Zostera species have been the most studied for the presence
of sulphated flavonoids, with no record of such flavonoids in Posidonia sp. A considerable accumulation of flavonoids such as luteolin 7-sulphate and luteolin
7,3′-disulphate has been observed in Z. marina as a strategy of chemical defence to
inhibit marine microorganism (Enerstvedt et al. 2016). In our study, luteolin 4′-glucoside and luteolin 5-(6″-malonylglucoside) are the only flavonoid glycosides that
we observed. The existence of luteolin 7-O-glucoside, diosmetin-7-O-glucoside (Z.
marina and Z. nana) and luteolin 7-O-glucoside (Z. noltii) suggests that Zostera
spp. are strong enough to synthesize these flavonoid derivatives in stressful aquatic
environment (Zidorn 2016; Subhashini et al. 2013). Similar to our findings, the
presence of malonylated flavone glycoside derivatives has also been observed in
Halophila stipulacea (Papenbrock 2012).
U. Kuzhiumparambil et al.