Synthesis, antibacterial and antioxidant activities of Thiazole-based Schiff base derivatives: a combined experimental and computational study

Fitsum Lemilemu; Mamaru Bitew; Taye B Demissie; Rajalakshmanan Eswaramoorthy; Milkyas Endale

doi:10.1186/s13065-021-00791-w

Synthesis, antibacterial and antioxidant activities of Thiazole-based Schiff base derivatives: a combined experimental and computational study

BMC Chem. 2021 Dec 23;15(1):67. doi: 10.1186/s13065-021-00791-w.

Authors

Fitsum Lemilemu¹, Mamaru Bitew², Taye B Demissie³, Rajalakshmanan Eswaramoorthy⁴, Milkyas Endale⁵

Affiliations

¹ Department of Applied Chemistry, Adama Science and Technology University, P.O. Box 1888, Adama, Ethiopia. fitsumlemilemu@gmail.com.
² Department of Applied Chemistry, Adama Science and Technology University, P.O. Box 1888, Adama, Ethiopia.
³ Department of Chemistry, University of Botswana, Notwane Rd, P/bag UB 00704, Gaborone, Botswana.
⁴ Department of Biomaterials, Saveetha Dental College and Hospital, Saveetha University, Chennai, 600 077, India.
⁵ Department of Applied Chemistry, Adama Science and Technology University, P.O. Box 1888, Adama, Ethiopia. milkyas.endale@astu.edu.et.

Abstract

Background: Thiazole-based Schiff base compounds display significant pharmacological potential with an ability to modulate the activity of many enzymes involved in metabolism. They also demonstrated to have antibacterial, antifungal, anti-inflammatory, antioxidant, and antiproliferative activities. In this work, conventional and green approaches using ZnO nanoparticles as catalyst were used to synthesize thiazole-based Schiff base compounds.

Results: Among the synthesized compounds, 11 showed good activities towards Gram-negative E. coli (14.40 ± 0.04), and Gram-positive S. aureus (15.00 ± 0.01 mm), respectively, at 200 μg/mL compared to amoxicillin (18.00 ± 0.01 mm and 17.00 ± 0.04). Compounds 7 and 9 displayed better DPPH radical scavenging potency with IC₅₀ values of 3.6 and 3.65 μg/mL, respectively, compared to ascorbic acid (3.91 μg/mL). The binding affinity of the synthesized compounds against DNA gyrase B is within - 7.5 to - 6.0 kcal/mol, compared to amoxicillin (- 6.1 kcal/mol). The highest binding affinity was achieved for compounds 9 and 11 (- 6.9, and - 7.5 kcal/mol, respectively). Compounds 7 and 9 displayed the binding affinity values of - 5.3 to - 5.2 kcal/mol, respectively, against human peroxiredoxin 5. These values are higher than that of ascorbic acid (- 4.9 kcal/mol), in good agreement with the experimental findings. In silico cytotoxicity predictions showed that the synthesized compounds Lethal Dose (LD₅₀) value are class three (50 ≤ LD₅₀ ≤ 300), indicating that the compounds could be categorized under toxic class. Density functional theory calculations showed that the synthesized compounds have small band gap energies ranging from 1.795 to 2.242 eV, demonstrating that the compounds have good reactivities.

Conclusions: The synthesized compounds showed moderate to high antibacterial and antioxidant activities. The in vitro antibacterial activity and molecular docking analysis showed that compound 11 is a promising antibacterial therapeutics agent against E. coli, whereas compounds 7 and 9 were found to be promising antioxidant agents. Moreover, the green synthesis approach using ZnO nanoparticles as catalyst was found to be a very efficient method to synthesize biologically active compounds compared to the conventional method.

Keywords: Antibacterial; Antioxidant; DFT analysis; Drug likeness; Molecular docking; Schiff base; Thiazole.