QUB-1942: a bioactive peptide from Phyllomedusa hypochodrialis skin secretion

In this thesis, QUB-1942, a peptide belonging to the phylloseptin family, was derived from the skin secretion of the orange-legged leaf frog, Phyllomedusa hypochondrialis. The peptide sequence was obtained through ‘shotgun’ cloning by constructing a cDNA library using frog skin secretion isolated mRNA.

The peptide was then synthesised by solid-phase peptide synthesis, purified by reversed-phase high-performance liquid chromatography, and structural-confirmed by matrix-assisted, laser desorption, ionisation, time-of-flight mass spectrometry. In bioassays, QUB-1942 showed inhibitory effects on the Gram-positive bacterium, Staphylococcus aureus (S. aureus ATCC CRM6538)at a concentration from 2 μM, the Gram-negative bacterium, Escherichia coli (E. coli ATCC CRM8739) at a concentration from 8 μM, and the yeast, Candida albicans (C. albicans ATCC CRM10231) at a concentration 64 μM. The minimum inhibitory concentration (MIC) value of the three microbes are 4 μM , 8 μM, 64 μM, respectively.