Identification and functional evaluation of a bioactive peptide QUB-2669 from the skin secretion of the American bullfrog Lithobates catesbeiana

  • Jingyu Tu

Student thesis: Masters ThesisMaster of Philosophy


Due to the prevalence of antimicrobial resistance, researching potential antibiotic substitutes against the multi-drug resistant bacteria has become a global concern. Amphibian skin, secreting many bioactive peptides, is a rich source of novel antimicrobial peptides. In this thesis, QUB-2669, derived from the skin secretion of the American bullfrog, Lithobates catesbeiana, was identified as a member of the ranatuerin-1 family. During the process of peptide synthesis, the methionine residue, containing a sulphur, was accidentally oxidised, therefore, another peptide named MetO-QUB-2669 was obtained. QUB-2669 presented moderate antimicrobial activities against Escherichia coli (minimum inhibitory concentration (MIC) was 32 μM) and Candida albicans (MIC was 64 μM), but was not sensitive against the Gram-positive bacterium Staphylococcus aureus (MIC was 128 μM). Apart from these, QUB-2669 showed slight antiproliferative effects against the cancer cell line NCI H838 at a concentration of 10-4 M. Besides, the haemolytic activity of QUB-2669 was lower than 20 % at the concentration range from 1 μM to 16 μM. Compared with QUB-2669, MetO-QUB-2669 showed lower antimicrobial, antiproliferative and haemolytic activities. Hence, QUB-2669 could be further modified by reducing the haemolytic ability and increasing the antimicrobial activities to become a potential candidate against microbial infections.

Thesis embargoed until 31 December 2026.
Date of AwardDec 2021
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SupervisorMei Zhou (Supervisor), Lei Wang (Supervisor) & Tianbao Chen (Supervisor)


  • Antimicrobial resistance
  • amphibian skin
  • bioactive peptides
  • ranatuerin-1 family
  • oxidised methionine

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