140
6 Carrageenans
this by chemically attaching to phagocytic cells such as macrophages by binding to
Toll-like receptors or pattern recognition cells. This has been demonstrated in mouse
T cells and in vivo experiments in laboratory mice. Carrageenan showed potential
use in ameliorating the allergic reaction from immune response. When given an oral
dosage of lambda carrageenan mice that have been treated with ovalbumin to trigger
an allergic reaction, the reduction in serum histamine release and ovalbumin-specific
IgE indicates a reduction in allergic reaction (Maruyama et al. 2005).
Immune modulation is also required where the immune activity needs to be
enhanced, for example, in the case of vaccination. Evidence also indicates that
carrageenans could potentially aid innate immune response against cancer cells by
enhancing the cytotoxic effect of the immune system’s lymphocytes and macrophages
such that the anticancer effect of carrageenan can be attributed to its immunomodulatory effect. In studies using oligosaccharides of kappa carrageenan of carrageenan
extracted from the red algae Kappaphycus striatum administered to mice which
had been induced with cancer (sarcoma S180), carrageenan enhanced the activity
of killer cells, inhibited cancer cell growth and increased macrophage phagocytosis
(Yuan et al. 2006). It should be noted that in the aforementioned study, the shortchain kappa carrageenans used are quite different from the high molecular weight
carrageenans which are commercially used in food industry. Sulfated polysaccharides have generally shown structure-dependent bioactivity such that the difference
in molecular weight means higher molecular weight carrageenans are not likely to
show the same immunomodulatory activity as oligosaccharide carrageenans. These
oligosaccharides are prepared from the acid hydrolysis of the longer-chain polysaccharide extracted from the red algae (Yuan et al. 2005), therefore making the polysaccharide carrageenans relevant in understanding the immunomodulatory activity of
the oligosaccharides.
6.7.12 Antiviral Activity
Carrageenans show relatively weak antiviral activity compared to other aquatic polymers which have been investigated for their potential antiviral activity. When tested
against denge viva virus DENV-1, DENV-2, DENVV-3 and DENV-4 in vero cells,
carrageenans only had antiviral effect of DENV-2. Carrageenan acted by inhibiting
the multiplication of the DENV-2 virus by preventing cell absorption and entry. This
effect was much less potent in DENV-3 and DENV-4 and completely ineffective in
DENV-1 (Talarico and Damonte 2007). However, even the activity against DENV-2
is dependent on the virus taking the normal route into the cell and being introduced
into the host cell at the same time as the virus or shortly after, once the normal entry
is bypassed or the virus is introduced at a longer time before the carrageenan, it then
has no antiviral infect and the DENV-2 virus is able to successfully infect the host.
6 Carrageenans
this by chemically attaching to phagocytic cells such as macrophages by binding to
Toll-like receptors or pattern recognition cells. This has been demonstrated in mouse
T cells and in vivo experiments in laboratory mice. Carrageenan showed potential
use in ameliorating the allergic reaction from immune response. When given an oral
dosage of lambda carrageenan mice that have been treated with ovalbumin to trigger
an allergic reaction, the reduction in serum histamine release and ovalbumin-specific
IgE indicates a reduction in allergic reaction (Maruyama et al. 2005).
Immune modulation is also required where the immune activity needs to be
enhanced, for example, in the case of vaccination. Evidence also indicates that
carrageenans could potentially aid innate immune response against cancer cells by
enhancing the cytotoxic effect of the immune system’s lymphocytes and macrophages
such that the anticancer effect of carrageenan can be attributed to its immunomodulatory effect. In studies using oligosaccharides of kappa carrageenan of carrageenan
extracted from the red algae Kappaphycus striatum administered to mice which
had been induced with cancer (sarcoma S180), carrageenan enhanced the activity
of killer cells, inhibited cancer cell growth and increased macrophage phagocytosis
(Yuan et al. 2006). It should be noted that in the aforementioned study, the shortchain kappa carrageenans used are quite different from the high molecular weight
carrageenans which are commercially used in food industry. Sulfated polysaccharides have generally shown structure-dependent bioactivity such that the difference
in molecular weight means higher molecular weight carrageenans are not likely to
show the same immunomodulatory activity as oligosaccharide carrageenans. These
oligosaccharides are prepared from the acid hydrolysis of the longer-chain polysaccharide extracted from the red algae (Yuan et al. 2005), therefore making the polysaccharide carrageenans relevant in understanding the immunomodulatory activity of
the oligosaccharides.
6.7.12 Antiviral Activity
Carrageenans show relatively weak antiviral activity compared to other aquatic polymers which have been investigated for their potential antiviral activity. When tested
against denge viva virus DENV-1, DENV-2, DENVV-3 and DENV-4 in vero cells,
carrageenans only had antiviral effect of DENV-2. Carrageenan acted by inhibiting
the multiplication of the DENV-2 virus by preventing cell absorption and entry. This
effect was much less potent in DENV-3 and DENV-4 and completely ineffective in
DENV-1 (Talarico and Damonte 2007). However, even the activity against DENV-2
is dependent on the virus taking the normal route into the cell and being introduced
into the host cell at the same time as the virus or shortly after, once the normal entry
is bypassed or the virus is introduced at a longer time before the carrageenan, it then
has no antiviral infect and the DENV-2 virus is able to successfully infect the host.