High and low-molecular weight crude sulfated polysaccharides
extracted from red algae were hydrolyzed using
different enzymes. Antioxidant activities of the produced fractions
were compared to those of the crude extracts. Viscozyme
and galactosidase hydrolysis of the high molecular-weight fractions
enhanced their scavenging activity for free DPPH radicals.
This is consistent with the phenolic content results in which the
viscozyme and galactosidase hydrolysates showed higher total
phenolic content relative to their mother fractions. Viscozyme
hydrolysates also exhibited higher scavenging activity for the peroxide free radical relative to their mother fractions. Scavenging
effect for both DPPH and peroxide radicals was found to
be dependent on the fraction concentration. Viscozyme hydrolysates
were superior to all other fractions in terms of their DPPH
and peroxide scavenging activities as well as their phenolic content.
The superior performance of viscozyme hydrolysate could be
attributed to the fact that it is a multifunctional enzyme that
hydrolyzes the mannans and galactans that predominantly exist
in red algae. This is confirmed by the presence of high mannose
and galactose contents in the viscozyme hydrolysates as determined
by HPLC analysis.
It could be suggested from the above that the antioxidant activity
is related to the phenolic content, chain length and type of
sugars present in the algal extracts. Thus, enzymatic hydrolysis of
the sulfated polysaccharide algal extracts using viscozyme produced
fractions with high antioxidant activities (>90%) that are
comparable with those of the commercial ascorbic acid antioxidant.
They also showed high antibacterial activities that exceeded
those of the two commercial antibiotics tetracycline and
cefuroxime.