Identification and evaluation of a bioactive peptide, QUB-2032, from the skin secretion of the frog, Odorrana andersonii

Then the peptide was synthesized chemically by means of solid-phase synthesis, purified by HPLC and structurally-confirmed by MALDI-TOF mass spectrometry to obtain sufficient material for the evaluation of multiple biological activities. <br><br>The bioactivity assays revealed that QUB-2032 had significant antimicrobial activities against the standard Gram-negative bacterium, Escherichia coli (E. coli ATCC CRM8739) and the standard Gram-positive bacterium, Staphylococcus aureus (S. aureus ATCC CRM6538) which showed a strong MIC and MBC value at a low concentration of only 4 μM. Also the peptide showed weak antimicrobial activity against the yeast Candida albicans (C. albicans ATCC CRM10231) for its MIC value was 64 μM and MBC was 128 μM. In the haemolysis assays, QUB-2032 showed a dose-dependent activity at concentrations from 32 μM to 512 μM, and the degree of haemolysis increased from 9.6% to 97.7%.

In the MTT anticancer cell proliferation assay, the peptide also showed significant inhibition against the cancer cell line, NCI-H838, at a concentration of 10-4 M with a value of 98.7%. To conclude, the peptide QUB-2032 showed strong bioactivities against E. coli, S. aureus and NCI-H838 cancer cells and also weak activity against C. albicans. However it showed high cytotoxicity on red blood cells.

The peptide could be considered, after optimization by modification, as a potential polypeptide drug for infections in the future.<br><br><i>Thesis is embargoed until 31 December 2028.</i><br>