Synthesis, antiproliferative and antimicrobial activities of (KLAKLAK)₂-NH₂ analogue containing nor-Leu and its conjugates with a second pharmacophore

Abstract

Peptides are a promising alternative of conventional medical drugs for the treatment of different diseases because they have no or have very few side effects owing to the natural mechanisms for their elimination. There are a lot of examples of drugs on the pharmaceutical market based on modified amino acids and peptides. Herein, we report the synthesis and studies on the antimicrobial peptide (KLAKLAK)₂-NH₂ where Leu is replaced by the unnatural amino acid nor-Leu. In addition, a second pharmacophore with well proven anticancer properties is introduced to the peptide moiety. All structures were synthesized by conventional solid phase peptide synthesis. The antiproliferative and antimicrobial activities were studied using MTT-dye reduction assay and disk-diffusion test, respectively. Biological activity assays showed that the introduction of nor-Leu in the primary structure of the parent compound does not lead to an increase in the antiproliferative activity. However, the combination with the second pharmacophore 1,8-naphtalimide in a hybrid structure 1,8-NphtG-(KNleAKNleAK)₂-NH₂ leads to a significant increase in the antiproliferative properties. The antimicrobial tests showed that all tested compounds exhibit antimicrobial activity. The peptide and the second pharmacophore had a synergistic effect. In combination with complete hydrolytic stability for 72 h in model systems, the compound 1,8-NphtG-(KNleAKNleAK)₂-NH₂ is the best candidate for a medical drug in the treatment of mammary gland type A adenocarcinoma (MCF-7) in combination with antimicrobial properties.

Keywords:

• Antiproliferative properties
• antibacterial properties
• caffeic acid
• (KLAKLAK)₂
• 1,8-naphthalimide
• unnatural amino acids
• nor-leucine

Acknowledgements

The authors would like to thank Testing center Global Test Ltd. for HPLC/MS/MS analysis.

Author contributions

Sirine Jaber: synthesis of target compounds, Veronica Nemska: antimicrobial activity study, Ivan Iliev: anticancer activity study and results interpretation, manuscript preparation, Elena Ivanova: anticancer activity study, Tsvetelina Foteva: antimicrobial activity study, Nelly Georgieva: antimicrobial studies conceptualization and interpretation, manuscript preparation, Ivan Givechev: HPLC/MS analysis and interpretation, Dimiter Tanev: HPLC/MS analysis and interpretation, Emilia Naydenova: conceptualization and manuscript preparation, Dancho Danalev: synthesis of target compounds, work conceptualization and manuscript preparation.

Disclosure statement

All authors declare that they have no conflict of interest. They are entitled to the authorship and have approved the final version of the manuscript.

Ethical approval

This study does not contain any studies with animals or humans performed by any of the authors.

Additional information

Funding

This work was developed as part of the project BG-RRP-2.004-0002 BiOrgaMCT funded by National Recovery and Resilience Plan, managing authority National Science Fund. The work is also part of the National Program “EUROPEAN SCIENTIFIC NETWORKS” of the Ministry of Science and Education of Bulgaria, project D01-278/05.10.2020.