352
16 Others Aquatic Biopolymers
vehicles, anti-inflammatory, wound healing and anticoagulant. It is mentioned in the
chapter on polyesters that the cuticle of the plant is linked to the epidermal wall by
layer of pectin such that its abundance correlates with that of cutin in plants. Aquatic
plants are the main source of pectin in the aquatic environment. The duckweed species
Spirodela polyrhiza, for example, contains up to 57% polysaccharide most of which
is pectin and xyloglucans (Sowinski et al. 2019) in their cell wall mass. Pectin is
also present in the cell walls of certain algae belonging to the Charophyceae taxa
(Domozych et al. 2012). This class of green algae is said to be the closest related
to terrestrial plants, and this is evidenced by the presence of a cell wall with similar
polymer composition as land plants.
16.6 Lignin
Lignin is a major evolutionary feature of plants. Terrestrial plants are believed to have
developed lignified cell walls as a means of adapting to survive on land (Boyce 2004).
It is therefore not expected to be needed in terrestrial plants. However, studies have
found lignin in aquatic plants (Chen et al. 2012; Thomas et al. 2009) albeit at a lower
amount compared to terrestrial plants. Lignins are complex aromatic heteropolymers
used by the plant to bind the cellulose microfibrils which are present in the cell wall,
and it also serves as a cross-linker for other cell wall components. This cross-linked
structure provides the stiffness and fortification within the xylem tissues in the plant
secondary cell walls that are needed for plants to have the erect structure.
Azolla has one of the highest lignin content at about 10%, while lignin content
in corn, an example terrestrial plant, is about 16% (Konda et al. 2015). A. pinnata,
a particular species of the Azolla plant, has up to 13.2% lignin (also contains 4.7%
starch, 12.8% cellulose and 10.1% hemicellulose). Duckweed has a lignin content of
12.2% (Yadav et al. 2017). The discovery of the presence of lignin in primitive green
algae and red algae strays from the accepted concept that lignin is an evolutionary
feature which allowed aquatic plants to evolve and adapt to terrestrial environment
(Martone et al. 2009).
16.7 Peptides from Frog Skin
Recent years have seen the increasing interest in the peptides within the skin of
some frog for their bioactive properties. These peptides include magainin-AM2,
tigerinin-1R and esculentin-2CHa. One of the most attractive bioactivities of these
frog skin-derived peptides is the antidiabetic activities. Peptides from frog skin can
stimulate insulin release, improve the sensitivity of the insulin, reduce the glucagon
concentration in the pancreas and the blood and also promote the proliferation of
the beta cells. It also has some lipid-lowering effects and promotes the expression
of genes coding for insulin secretion. These have been confirmed in in vivo studies
16 Others Aquatic Biopolymers
vehicles, anti-inflammatory, wound healing and anticoagulant. It is mentioned in the
chapter on polyesters that the cuticle of the plant is linked to the epidermal wall by
layer of pectin such that its abundance correlates with that of cutin in plants. Aquatic
plants are the main source of pectin in the aquatic environment. The duckweed species
Spirodela polyrhiza, for example, contains up to 57% polysaccharide most of which
is pectin and xyloglucans (Sowinski et al. 2019) in their cell wall mass. Pectin is
also present in the cell walls of certain algae belonging to the Charophyceae taxa
(Domozych et al. 2012). This class of green algae is said to be the closest related
to terrestrial plants, and this is evidenced by the presence of a cell wall with similar
polymer composition as land plants.
16.6 Lignin
Lignin is a major evolutionary feature of plants. Terrestrial plants are believed to have
developed lignified cell walls as a means of adapting to survive on land (Boyce 2004).
It is therefore not expected to be needed in terrestrial plants. However, studies have
found lignin in aquatic plants (Chen et al. 2012; Thomas et al. 2009) albeit at a lower
amount compared to terrestrial plants. Lignins are complex aromatic heteropolymers
used by the plant to bind the cellulose microfibrils which are present in the cell wall,
and it also serves as a cross-linker for other cell wall components. This cross-linked
structure provides the stiffness and fortification within the xylem tissues in the plant
secondary cell walls that are needed for plants to have the erect structure.
Azolla has one of the highest lignin content at about 10%, while lignin content
in corn, an example terrestrial plant, is about 16% (Konda et al. 2015). A. pinnata,
a particular species of the Azolla plant, has up to 13.2% lignin (also contains 4.7%
starch, 12.8% cellulose and 10.1% hemicellulose). Duckweed has a lignin content of
12.2% (Yadav et al. 2017). The discovery of the presence of lignin in primitive green
algae and red algae strays from the accepted concept that lignin is an evolutionary
feature which allowed aquatic plants to evolve and adapt to terrestrial environment
(Martone et al. 2009).
16.7 Peptides from Frog Skin
Recent years have seen the increasing interest in the peptides within the skin of
some frog for their bioactive properties. These peptides include magainin-AM2,
tigerinin-1R and esculentin-2CHa. One of the most attractive bioactivities of these
frog skin-derived peptides is the antidiabetic activities. Peptides from frog skin can
stimulate insulin release, improve the sensitivity of the insulin, reduce the glucagon
concentration in the pancreas and the blood and also promote the proliferation of
the beta cells. It also has some lipid-lowering effects and promotes the expression
of genes coding for insulin secretion. These have been confirmed in in vivo studies