Cationic Clitoria ternatea Seed Peptide as a Potential Novel Bioactive Molecule

Background: While several biologics have been reported from different parts of Clitoria ternatea, a herbaceous climber of the family Fabaceae, specific production of cationic peptides other than cyclotides (<3.7 kDa) has barely been investigated, or their bioactive potential been looked into. Objective: The study aims to uncover potential bioactivities and characteristics of novel cationic peptides from C. ternatea seeds. Methods: C. ternatea seed cationic peptide purified by simple and cost-effective procedures was analyzed by electrophoresis and mass spectrometry. Antimicrobial efficacy was evaluated against bacterial and fungal pathogens. Antioxidant potential was quantified by in vitro antioxidant assays. Physicochemical characterization and Tandem mass spectrometry were performed. Results: An 8.5 kDa cationic peptide purified from C. ternatea seeds was active against Candida albicans, Staphylococcus aureus, Aeromonas hydrophila and Escherichia coli at a minimum inhibitory concentration in the range of 8-32 μg/ml. This activity was totally uncompromised at pH 5-8 or after 1 h of heat treatment at 70-80ºC, but was sensitive to protease treatment. Concentration-dependent free-radical scavenging activity and ferric-reducing capacity demonstrated the antioxidant potential of the peptide. Tandem MS analysis of trypsin-digested peptide based on shotgun proteomics detected matching peptide sequences with one or two cysteine residues but had low sequence coverage (≤17%) to known sequences in the C. ternatea protein database. Taken together, the distinct characteristics of this novel 8.5 kDa peptide clearly distinguish it from known cyclotides of C. ternatea. Conclusions: Insights have been obtained into the functional characteristics of what appears to be a novel cationic peptide from C. ternatea seeds, exhibiting significant antimicrobial and antioxidant activities.