Spiro heterocycles bearing piperidine moiety as potential scaffold for antileishmanial activity: synthesis, biological evaluation, and studies.

New spiro-piperidine derivatives were synthesised via the eco-friendly ionic liquids in a one-pot fashion. The antileishmanial activity against promastigote and amastigote forms highlighted promising antileishmanial activity for most of the derivatives, with superior activity compared to miltefosine. The most active compounds and exhibited sub-micromolar range of activity, with IC values of 0.89 µM and 0.50 µM, respectively, compared to 8.08 µM of miltefosine. Furthermore, the antileishmanial activity reversal of these compounds folic and folinic acids displayed comparable results to the positive control trimethoprim. This emphasises that their antileishmanial activity is through the antifolate mechanism targeting DHFR and PTR1. The most active compounds showed superior selectivity and safety profile compared to miltefosine against VERO cells. Moreover, the docking experiments of and against -PTR1 rationalised the observed activities. Molecular dynamics simulations confirmed a stable and high potential binding to -PTR1.