Purpose This study aimed to design, synthesize, characterize, and biologically evaluate fluorobenzaldehyde-based Schiff base derivatives (3a–3j) of 4-hydrazinyl-7 H-pyrrolo[2,3-d]pyrimidine as potential antimicrobial and cytotoxic agents, and to assess the effect of fluorine substitution on activity using SAR and molecular docking studies. Methods The target compounds (3a–3j) were synthesized by acid-catalyzed condensation of 4-hydrazinyl-7 H-pyrrolo[2,3-d]pyrimidine with fluorinated benzaldehydes in ethanol under reflux, and characterized by FT-IR, ¹H NMR, UV–vis, and elemental analysis, confirming azomethine (C = N) formation. Antibacterial activity was evaluated against Gram-positive (Staphylococcus aureus MCC 2408 and Bacillus subtilis MCC 2010) and Gram-negative (Escherichia coli MCC 2412 and Pseudomonas aeruginosa MCC 2080) strains using agar well diffusion and broth microdilution assays, with Ciprofloxacin as the reference drug. Antifungal activity was assessed against Candida albicans (MCC 1439) and Saccharomyces cerevisiae (MCC 1033) using disk diffusion and microdilution methods, with Fluconazole as a reference drug. Cytotoxicity was evaluated using Artemia salina lethality assay. Molecular docking studies were performed using AutoDock 4.0. Results The synthesized derivatives exhibited broad-spectrum antimicrobial activity, Compounds 3e, 3f, 3 g and 3 h shows superior or comparable activity to the reference drugs in several cases, with compound 3 g showing the highest inhibition zone (33 mm) against P. aeruginosa and compound 3a, 3b, 3c and 3d showing the lowest or no-detectable inhibition zone (0 mm) against B. Subtilis. Statistical analysis (ANOVA, p < 0.05) confirmed the significance of the results. Cytotoxicity screening revealed moderate toxicity, with LD50 values between 3.83 × 10− 4 and 9.81 × 10− 4 M. molecular docking studies showed that compound 3i (binding energy − 9.2 kcal/mol), 3 h (binding energy − 9.0 kcal/mol), and 3 g (binding energy − 8.7 kcal/mol), exhibited comparatively enhanced antibacterial activity. The compound 3i shows highest binding energy − 9.2 kcal/mol than the antibacterial stranded reference drug Ciprofloxacin (binding energy − 7.8 kcal/mol). Compound 3 g (binding energy − 8.4 kcal/mol), 3i (binding energy − 8.5 kcal/mol) and 3j (binding energy − 8.3 kcal/mol) had higher a binding energy than the antifungal standard reference drug Fluconazole (binding energy − 6.7 kcal/mol). Docking studies showed favourable binding energy of compound 3i (up to − 9.2 kcal/mol against DHFR and − 8.5 kcal/mol against ERG11), with multiple hydrogen bonding and hydrophobic interactions at the active sites, correlating well with experimental antimicrobial potency. Conclusion Combined synthetic, biological, cytotoxic, and computational results show that strategic fluorine substitution enhances antimicrobial activity and target binding, highlighting this scaffold as a promising lead for further development of novel antimicrobial agents. Graphical Abstract

Design, Synthesis, Spectral Characterization, and Biological Evaluation of Fluorobenzaldehyde-Based Schiff Base Derivatives of 4-Hydrazinyl-7 H-pyrrolo[2,3-d]pyrimidine

期刊论文
发表日期：

2026年5月19日

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Ravindra Patil,
Sandip Nandre,
Vikas Patil,
Sharad R. Patil,
S. R. Patil

摘要

Purpose

This study aimed to design, synthesize, characterize, and biologically evaluate fluorobenzaldehyde-based Schiff base derivatives (3a–3j) of 4-hydrazinyl-7 H-pyrrolo[2,3-d]pyrimidine as potential antimicrobial and cytotoxic agents, and to assess the effect of fluorine substitution on activity using SAR and molecular docking studies.

Methods

The target compounds (3a–3j) were synthesized by acid-catalyzed condensation of 4-hydrazinyl-7 H-pyrrolo[2,3-d]pyrimidine with fluorinated benzaldehydes in ethanol under reflux, and characterized by FT-IR, ¹H NMR, UV–vis, and elemental analysis, confirming azomethine (C = N) formation. Antibacterial activity was evaluated against Gram-positive (Staphylococcus aureus MCC 2408 and Bacillus subtilis MCC 2010) and Gram-negative (Escherichia coli MCC 2412 and Pseudomonas aeruginosa MCC 2080) strains using agar well diffusion and broth microdilution assays, with Ciprofloxacin as the reference drug. Antifungal activity was assessed against Candida albicans (MCC 1439) and Saccharomyces cerevisiae (MCC 1033) using disk diffusion and microdilution methods, with Fluconazole as a reference drug. Cytotoxicity was evaluated using Artemia salina lethality assay. Molecular docking studies were performed using AutoDock 4.0.

Results

The synthesized derivatives exhibited broad-spectrum antimicrobial activity, Compounds 3e, 3f, 3 g and 3 h shows superior or comparable activity to the reference drugs in several cases, with compound 3 g showing the highest inhibition zone (33 mm) against P. aeruginosa and compound 3a, 3b, 3c and 3d showing the lowest or no-detectable inhibition zone (0 mm) against B. Subtilis. Statistical analysis (ANOVA, p < 0.05) confirmed the significance of the results. Cytotoxicity screening revealed moderate toxicity, with LD₅₀ values between 3.83 × 10^− 4 and 9.81 × 10^− 4 M. molecular docking studies showed that compound 3i (binding energy − 9.2 kcal/mol), 3 h (binding energy − 9.0 kcal/mol), and 3 g (binding energy − 8.7 kcal/mol), exhibited comparatively enhanced antibacterial activity. The compound 3i shows highest binding energy − 9.2 kcal/mol than the antibacterial stranded reference drug Ciprofloxacin (binding energy − 7.8 kcal/mol). Compound 3 g (binding energy − 8.4 kcal/mol), 3i (binding energy − 8.5 kcal/mol) and 3j (binding energy − 8.3 kcal/mol) had higher a binding energy than the antifungal standard reference drug Fluconazole (binding energy − 6.7 kcal/mol). Docking studies showed favourable binding energy of compound 3i (up to − 9.2 kcal/mol against DHFR and − 8.5 kcal/mol against ERG11), with multiple hydrogen bonding and hydrophobic interactions at the active sites, correlating well with experimental antimicrobial potency.

Conclusion

Combined synthetic, biological, cytotoxic, and computational results show that strategic fluorine substitution enhances antimicrobial activity and target binding, highlighting this scaffold as a promising lead for further development of novel antimicrobial agents.

Graphical Abstract