Typically, antimicrobial peptides (AMPs) are short positive charged peptides 
serving a key role in innate immunity as well as antimicrobial activity. 
Discovering novel therapeutic agents is considered as an undeniable demand due 
to increasing microbial species with antibiotic resistance. In this direction, 
the unique ability of AMPs to modulate immune responses highlighted them as 
novel drug candidates in the field of microbiology. Patients affected by 
leishmaniasis; a neglected tropical disease, confront serious problems for their 
treatment including resistance to common drugs as well as toxicity and high cost 
of therapy. So, there is a need for development of new drug candidates to 
control the diseases. Jellein, a peptide derived from royal jelly of honeybee 
has been shown to have promising effect against several bacterial and fungal 
species. In current study, anti-leishmanial effect of Jellein and its lauric 
acid conjugated form was investigated against two forms of Leishmania major (L. 
major) parasite. Moreover, cytotoxic effect of these peptides was studied in 
THP1 cell line and human Red Blood Cells (RBCs). Furthermore, the mechanism of 
action of peptides on L. major promastigotes was assessed through different 
methods. The results demonstrated that, conjugation of lauric acid to Jellein 
not only had no effect on the elevation of antimicrobial activity but also 
halted it completely. Moreover, Jellein caused a limitation in the number of L. 
major promastigotes by pore formation as well as changing the membrane potential 
rather than induction of apoptosis or activation of caspases.