Advances in Coordination Chemistry of Schiff Base Complexes: A Journey from Nanoarchitectonic Design to Biomedical Applications

Since the discovery of Schiff bases over one and a half centuries ago, there has been tremendous research activity in the design of various Schiff bases and examination of their diverse structures and versatile applications. This family of compounds has continued to captivate many research groups due to the simplicity of their synthesis through the condensation of amines with carbonyl compounds. While conventional synthesis has been the most widely used, green synthetic methodologies have been also explored for this reaction, including sonication, microwave-assisted, natural acid-catalyzed and mechanochemical syntheses as well as utilizing ionic liquid solvents or deep eutectic solvents. Schiff bases have been utilized as excellent ligands for coordination to transition metals and late transition metals (lanthanides and actinides). These Schiff base compounds can be mono-, di-, or polydentate ligands. The aim of this review is to examine the biological applications of Schiff base complexes over the past decade with particular focus on their antimicrobial, antiviral, anticancer, antidiabetic, and anti-inflammatory activity. Schiff base complexes have been found effective in combating bacterial and fungal infections with numerous examples in the literature. The review addressed this area by focusing on the very recent examples while using tables to summarize the vast breadth of research according to the metallic moieties. Viruses have continued to be a target of many researchers in light of their continuous mutations and impact on human health, and therefore some examples of Schiff base complexes with antiviral activity are described. Cancer continues to be among the leading causes of death worldwide. In this article, the use of Schiff base complexes for, and the mechanisms associated with, their anticancer activity are highlighted. The production of reactive oxygen species (ROS) or intercalation with DNA base pairs leading to cell cycle arrest were the main mechanisms described. While there have been some efforts made to use Schiff base complexes as antidiabetic or anti-inflammatory agents, there are limited examples when compared with antimicrobial and anticancer studies. The conclusion of this review highlights the emerging areas of research and future perspectives with an emphasis on the potential uses of Schiff bases in the treatment of infectious and noninfectious diseases.

Biosynthesis and health promoting traits of green synthesized cobalt oxide nanoparticles

Nanomedical applications have increased significantly. This work aimed to fabricate and characterize cobalt oxide nanoparticles (CoOnps) synthesized biologically via aqueous Alhagi maurorum extract and evaluate their cytotoxic and antimicrobial impacts. Green-synthesized CoOnps were prepared and analyzed using UV-Vis spectrophotometer UV-vis, Scanning electron microscopy (SEM), Transmission electron microscopy TEM, Energy dispersive X-ray analysis EDAX, Fourier transform infrared, FTIR, and X-ray diffraction (XRD). In vitro traits of green-synthesized CoOnps were studied on ovarian cancer cells (SKOV3) using a Sulforhodamine B (SRB) method. The cytotoxic effect and IC50 were estimated. Moreover, concentrations of 10, 30, 40, 70, 100, 200, 300, 400 and 500 μg/mL CoOnps were applied to investigate their antimicrobial effect against Listeria, Staphylococcus aureus and Streptococcus as gram +ve pathogenic bacteria, Bifidobacterium bifidum 2203, Bifidobacterium bifidum LMG 10,645, Bifidobacterium breve LMC 017, Bifidobacterium angulatum 2238 and Bifidobacterium longum ATCC 15,707 as probiotics, E. coli as gram -ve bacterial model and yeast strain Candida albicans. CoOnps showed anti-ovarian cancer effects at 24.02 μg/mL. Furthermore, it exerted antimicrobial activity versus Listeria, Streptococcus, S. aureus, and E. coli were 31.66 ± 0.88, 24.33 ± 2.08, 25.66 ± 0.33, and 33.00 ± 6.08; however, they did not suppress the growth of Candida albicans and all tested Bifidobacterial strains up to concentrations of 500 μg/mL with significant difference compared to all concentrations p < 0.05. Green synthesis of CoOnps is a low-cost, eco-friendly and easily prepared method. Its impressive features as cytotoxic SKOV3, a cell line ovarian cancer and antibacterial effect for some gram +ve and -ve bacteria, besides maintaining probiotics, could candidate them as competitive agents for medical, pharmacological, agricultural and food applications.