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.