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Abstract
Synthesis, physical properties and biological activity of Schiff bases based on chitosan bearing quinolinone moiety
Chitosan Cs was exposed to react with 4-hydroxy-6-methyl-2,5-dioxo-5,6-dihydro-2H-pyrano[3,2-c]quinolone-3-carboxaldehyde B in acid media to form Schiff base CsP, which shows high adsorption of remazol red (RR) dye, which was used in textile industry. Also, N-methyl-4-hydroxy-2H-quinolin-2-one-3-carboxaldehyde C was reacted with Chitosan in acid medium to form Schiff base CsQ, which possess a higher biological activity.
New composites of chitosan Schiff bases bearing quinolinone and pyranoquinolinone moieties loaded with silver nanoparticles were prepared using Ag/NPs (with a ratio of 1%) with respect to chitosan Schiff base.
A pure chitosan and all the new Schiff bases (CsQ, CsP, CsQ/Ag, and CsP/Ag) have been tested in terms of their cytotoxic effects in cancer cells, namely, liver (HepG-2), colon (HCT-116), and breast (MCF-7). The inhibitory effect of the synthesized compounds against tumor cell lines was compared with 5-fluorouracil as a positive control. The composite CsQ/Ag revealed the highest antiproliferative activity toward the three cancer cell lines with minimum IC50 value compared to the chemotherapeutic agent 5-fluorouracil.
Antioxidant activities of chitosan Schiff bases were measured using the scavenging activity assay on the DPPH radical. All samples exhibited DPPH scavenging ability and the concentration of sample influenced the percentage of DPPH. It`s clear that loading Schiff bases with Ag/NPs increase the DPPH radical-scavenging activity. Where, the composite CsQ/Ag showed relatively high antioxidant activity.
The new Schiff base CsP showed a great ability to adsorb textile carcinogenic organic dye from aqueous solution (qm is 344.4 mg/g).Several factors affected the adsorption capacity of this synthesized sample: temperature, pH, initial concentration of the dye solution, dose of adsorbent, and contact time with the RR dye. The results obtained showed that chitosan Schiff base achieved a dye uptake percentage of 100% after a period of dye contact time not exceeding 20 min. Thermodynamic parameters such as change in enthalpy, change in Gibbs free energy, and change in entropy were calculated, and the results indicated that the adsorption process was spontaneous and endothermic. Pseudo-first-order, pseudo-second-order, intra-particle diffusion, and Elovich adsorption kinetic models along with Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich adsorption isotherms models were utilized in this study. The sorption process was better fitted to pseudo-second-order equation and the Freundlich model.