| dc.description.abstract | Pathogenesis of several diseases has been attributed to free radical modification of biomolecules within
the body, which can be prevented or treated with antioxidants, especially those of natural origin. Some
plant peptides have been reported to be effective antioxidants. Cysteine-stabilised peptide content of
Morinda lucida leaf was extracted and purified using solvent extraction, column chromatography, reversephase
high performance liquid chromatography and the type of cysteine-stabilised peptide present was
determined using matrix-assisted laser desorption ionisation time of flight mass spectrometry analysis and
ninhydrin staining. Antioxidant activities of the partially purified peptide fraction were evaluated using
in vitro models. The presence of linear cysteine-stabilised peptide with masses ranging from 3.601 to 3.678 kDa
and having three disulphide bonds was confirmed. Partially purified peptide fraction exhibited 2,2-diphenyl-
1-picrylhydrazyl radical scavenging activity and ferric reducing antioxidant power, which is statistically
compared with that of butylated hydroxytoluene but displayed statistically lower total antioxidant capacity
compared to glutathione. Nitric oxide scavenging activity of partially purified peptide fraction was statistically
lower compared to ascorbic acid. Hydroxyl radical scavenging activity of partially purified peptide fraction
was significantly higher (p<0.05) compared with that of glutathione at higher concentrations. Cysteinestabilised
peptide, identified for the first time in M. lucida leaf, possesses antioxidant properties and they may
be effective in the management of reactive oxygen species-mediated pathological conditions but not reactive
nitrogen species-mediated pathological conditions. | en_US |
