Synthesis of new pyrazolo[5,1-c][1,2,4]triazines with antifungal and antibiofilm activities

Fungal infection is a significant global health challenge in part due to the emergence of strains exhibiting resistance to nearly all classes of antifungals. This underscores the urgent need for the development of new antifungal agents that can circumvent this burgeoning problem. For the present research, a new selected set of pyrazolo[5,1-c][1,2,4]triazine derivatives 3a–g was prepared in high yield via the reaction of N1-(5-methylpyrazol-3-yl)hydrazonoyl chloride 1 with morpholine, thiomorpholine, 4-phenylpiperidine and N-(substituted)piperazines. The new compounds were evaluated for their in vitro antifungal and antibacterial activities. The screening revealed compounds with specific activity against pathogenic fungi, including Candida albicans, Candida auris, and Cryptococcus. Compound 3d, which incorporated N-phenylpiperazine moiety, exhibited the highest growth inhibition against C. albicans with a minimum inhibitory concentration of 16 µg/mL. The compounds were superior to fluconazole in inhibiting Candida biofilm mass at sub-inhibitory concentration. Furthermore, the MTS assay confirmed that compounds 1 and 3d exhibited an excellent toxicity profile (not toxic, up to 256 μg/mL, for mammalian cells). Collectively, the presented results demonstrate that the synthesized pyrazolo-triazines warrant further exploration for potential use as antifungal agents.