The discovery of the novel peptide QUB-2049 from the skin secretion of Odorrana versabilis

In this thesis, QUB-2049, a bioactive peptide belonging to the nigrocin superfamily, was extracted from the frog Odorrana versabilis by ‘shotgun’ molecular cloning. A substantial quantity of peptide was obtained by solid-phase synthesis, and this was purified by reversed-phase high performance liquid chromatogram (RP-HPLC) and the molecular mass was determined by Matrix-Assisted Laser Desorption Ionisation-Time of flight (MALDI-TOF) mass spectrometry to ensure that the pure peptide (QUB-2049) was obtained.

The functional assay was carried out on the peptide. Then QUB-2049 was tested in several biological experiments and found to inhibit the growth of Escherichia coli (E. coli ATCC CRM 8739) (Minimum inhibitory concentration = 8 μM), Staphylococcus aureus (S.aureus ATCC CRM 6538) ((MIC = 64 μM), and Candida albicans (C.albicans ATCC CRM 10231) (MIC = 128 μM). In the haemolysis assay peptide QUB-2049 showed an obvious haemolytic activity (% haemolysis >10) at concentrations ≥16 μM. The result of the antiproliferative assay showed that QUB-2049 had inhibitory activity against ATCC H838 cells at a concentration of 100 µM in which a significant loss of cell viability was observed.

According to the experimental results, peptide QUB-2049 is a good candidate for developing an antibacterial agent against Gram negative bacteria, but optimisation would be needed to reduce its haemolytic effects.<br><br><p><i>Thesis embargoed until 31 December 2026</i><i>.</i></p>