Synthesis, Characterization, and Biological Evaluation of Tetrahydropyrimidines: Dual-Activity and Mechanism of Action

Abstract

In this paper, the synthesis, characterization, and biological evaluation of the novel tetrahydropyrimidines-THPMs are described. THPMs are well-known for wide pharmacological activities such as antimicrobial, anticancer, antiviral, etc. This research includes obtained results of in vitro antimicrobial, anticancer, and α-glucosidase inhibitory activities of the eleven novel THPMs. An antibiotic assessment was done against five bacteria (two Gram-positive and three Gram-negative) and five fungi by determining the minimal inhibitory concentration (MIC), using the broth tube dilution method. The most active antibacterial compounds were 4a, 4b, and 4d, while the best antifungal activity was shown by 4e, 4f, and 4k. The lowest MIC value (0.20 mg/mL) was measured for 4e, 4f, and 4k against the Trichophyton mentagrophytes. Moreover, examining the α-glucosidase inhibitory activity revealed the compound 4g as the one with the best activity. The cytotoxic activity was performed on the tumor cell lines (HeLa, K562, and MDA-MB-231) and normal cells (MRC-5). The best antitumor activity was shown by compounds 4b and 4k against HeLa cell lines. The influence on cell cycle and mechanism of action of the most active compounds were examined too. Compound 4b had good antibacterial and anticancer activities, while 4k showed promising antifungal and anticancer activities.

Keywords: Biginelli reaction; anticancer; antimicrobial; apoptosis; tetrahydropyrimidine.

Scheme 1

Substrate scope in the synthesis of tetrahydropyrimidines 4a–k. Reaction conditions: (a) aldehyde and N-methylthiourea, dioxane/CHCl₃, room temperature, (b) methyl acetoacetate, HCl, 2-amino-1-(4-nitrophenyl)-1,3-propanediol (ANP), room temperature.

Figure 1

MERCURY [29] drawing of the molecular structure of compound 4j with labeled non-H atoms. Displacement ellipsoids are shown at 30% probability. Symmetry code: (i) −x, −y+1, −z+2.

Figure 2

MERCURY [29] drawing showing crystal packing of 4-(4′-benzoyloxy-3′-methoxyphenyl)- 1,2,3,4-tetrahydro-1,6-dimethyl-2-thioxopyrimidine-5-carboxylate (4j) viewed along the a axis. Intramolecular N—H•••O and C—H•••O contacts are shown as dashed lines. Intermolecular C9—H9•••S1^{1(x, y+1, z)} contacts (dashed line) connect molecules in a head-to-tail manner along the b axis.

Figure 3

MERCURY [29] drawing of crystal packing of 4-(4′-benzoyloxy-3′-methoxyphenyl)- 1,2,3,4-tetrahydro-1,6-dimethyl-2-thioxopyrimidine-5-carboxylate (4j) showing intermolecular C—H•••O contacts (dashed line) connecting molecules in a head-to-tail manner along the a axis. Symmetry codes: ²: x−1, y, z; ³: x+1, y, z.

Figure 4

Cell-cycle phase distribution of control HeLa cells and HeLa cells incubated with IC₅₀ (A) and 2 IC₅₀ (B) concentrations of compounds 4b and 4k during 24 h. The data shown represent the average ± standard deviation of two independent experiments.

Figure 5

Photomicrographs of acridine orange/ethidium bromide-stained control HeLa cells and HeLa cells incubated with 2IC₅₀ concentrations of compounds 4b and 4k during 24 h (magnification 20×). Representative photomicrographs are shown.