Seaweeds: A Promising Source for Sustainable Development - Environmental Sustainability: Role of Green Technologies - page 72

6.10 Agglutination, Coagulation,

and the Stimulation of Cell
Migration Properties

6.11 Antilipemic,

Hypocholesterolemic,
Hypoglycemic, Hypotensive,
and Related Activities

Macromolecule recognition processes are
common in cells and their specifi city is their
most important characteristic. Many research
programs exploit recognition events, and these
have become the focus areas of research in
biology, chemistry, medicine, and pharmacology.
Biological reactions that involve recognition
events include processes such as cell agglutina-
tion and coagulation, the stimulation of cell
migration, and fertilization. Lectins, sometimes
referred to as hemagglutinins or agglutinins, are
glycoproteins with an ability to agglutinate red
blood cells (Boyd and Reguera 1949 ). Various
polysaccharides are present on cell surfaces
and as a result many cells including microbes
and yeasts. Tumor cells (Hori et al. 1986 ) and
erythrocytes are selectively agglutinated by lectins
(Chen et al. 1995 ).
Lectins are inhibited by sugars of the same
type as those on the surface of the cells being
agglutinated (Sharma and Sahni 1993 ). They are
useful in exploring properties of biological
structures and processes and have found applica-
tions in biology, cytology, biochemistry, medi-
cine, and food science and technology. Lectins
from Codium sp. have been developed into
commercially available reagents and are rou-
tinely used in biochemical studies. Lectins with
hemagglutinating properties occur in a verity of
red, green, and brown algae (Rogers and Hori
1993 ; Shanmugam et al. 2002 ). They react with
a wide array of erythrocytes including human
blood group types. Agglutination reactions with
human blood groups have led to their use in
assays for blood typing. Lectins are also used to
characterize cell-surface polysaccharides or to
examine cell-binding patterns in lectinosorbent
assays (Wu et al. 1998 ). Lectins from Codium
fragile subspecies tomentosoides have been
developed into a histochemical reagent by coupling
them to colloidal gold, forming a lectin-gold
conjugate. This conjugate is useful for studies of
the surface topography of cells of animal tissues
(Griffi n et al. 1995 ).

High plasma cholesterol levels and high blood
pressure are the causes of cardiovascular disease.
Some macroalgal polysaccharides and fi bers
such as alginate, carrageenan, funoran, fucoidan,
laminaran, porphyran, and ulvan have been
noted to produce hypocholesterolemic and hypo-
lipidemic responses due to reduced cholesterol
absorption in the gut (Panlasigui et al. 2003 ).
This is often coupled with an increase in the fecal
cholesterol content and a hypoglycemic response
(Dumelod et al. 1999 ). Others have reported low-
ering of systolic blood pressure (antihypertensive
responses) and lower levels of total cholesterol,
free cholesterol, triglyceride, and phospholipid in
the liver (Nishide and Uchida 2003 ). Evidence
suggests that ulvan as a dietary fi ber plays a pro-
tective role in the rate such that it modulates the
stimulatory effect of mucin secretion by goblet
cells into the colon (Barcelo et al. 2000 ). A crude
methanolic extract from Pelvetia babingtonii
showed potent -glucosidase inhibitory activity

which could make it effective in suppressing
postprandial hyperglycemia (Ohta et al. 2002 ).
Hypolipidemic activities have been identifi ed
in ethanolic extracts of Solieria robusta , Lyngarisa
stellata , Colpomenia sinuosa , Spatoglossum
asperum , and Caulerpa racemosa , as shown by
decreases in the total serum cholesterol, tri-
glyceride, and low-density lipoprotein choles-
terol levels in rats (Ara et al. 2002 ). PGE2 from
Gracilaria lichenoides has antihypertensive
properties when administered intravenously to
hypertensive rats. Some of these substances,
most notably the fi bers, are likely to be exploited
by nutraceutical companies that market them as
health products.

ʱ

6.12 Antioxidants from Seaweeds

Marine algae are constantly exposed to various
environmental conditions including freezing,
carbon limitation, water stress, and heat stress.