Synthesis, molecular docking and biological evaluation of bis-pyrimidine Schiff base derivatives

Heterocyclic pyrimidine nucleus, which is an essential base component of the genetic material of deoxyribonucleic acid, demonstrated various biological activities. A series of bis-pyrimidine Schiff bases were synthesized and screened for its antimicrobial and anticancer potentials. The molecular docking study was carried to find the interaction between active molecules with receptor.

The structures of synthesized bis-pyrimidine Schiff bases were confirmed by spectral studies. The synthesized bis-pyrimidine derivatives were evaluated for their antimicrobial activity (MIC = µmol/mL) against selected Gram positive; Gram negative bacterial and fungal strains by tube dilution method. The anticancer activity (IC₅₀ = µmol/mL) of the synthesized compounds was determined against human colorectal carcinoma (HCT116) cancer cell line by Sulforhodamine B (SRB) assay. Molecular docking studies provided information regarding the binding mode of active bis-pyrimidine Schiff bases with the cyclin-dependent kinase 8 (CDK8) receptor.

The antimicrobial screening results indicated that compounds, q1 (MIC_bs = 0.83 µmol/mL), q16 (MIC_an = 1.54 µmol/mL and MIC_ec = 0.77 µmol/mL), q1 and q19 (MIC_ca = 0.41 µmol/mL) and q20 (MIC = 0.36 µmol/mL) are the most active ones. Compounds q1 (IC₅₀ = 0.18 µmol/mL) have emerged as potent anticancer molecule against human colorectal carcinoma cancer cell line than the reference drug, 5-fluorouracil. Molecular docking studies indicated that compound q1 (the most active molecule) has the maximum hydrogen bond interaction (four) and π-π stacking (three) network among the bis-pyrimidine Schiff bases. Graphical abstract Graphical illustration of predicted binding mode of bis-pyrimidine Schiff bases in the active site of CDK8. a. Compound 1 (magenta color), b. Compound 5 (green color), c. Compound 8 (red color), d. Compound 13 (split pea color).