No abstract

Twelve novel substituted 2‐chloroquinoline‐3‐carboxamide derivatives were prepared from acetanilides using the Vilsmeier–Haack reaction, producing 2‐chloro‐3‐carbaldehyde quinolines, followed by oxidation of the 3‐carbaldehyde to the carboxylic acid and coupling this group with various anilines. The structures of the synthesized compounds were confirmed by NMR, mass spectrometry, and single crystal X‐ray diffraction. The chemical shifts of H‐5 and H‐8 were shown to be influenced by the substituent at C‐6. The substituent at C‐6 was also seen to affect the chemical shift of C‐5, C‐7, and C‐8, with C‐5 and C‐7 being more shielded in 5j (F substituted) in comparison with 5g (Cl substituted) and 5d (CH3 substituted). The compounds showed weak activity in the mM range against Gram‐positive and Gram‐negative bacteria of which 5b, 5d, and 5f showed the best activity with minimum bactericidal concentration values for 5b being 3.79 mM against methicillin‐resistant Staphylococcus aureus and 5d and 5f having minimum bactericidal concentration values of 3.77 and 1.79 mM against S. aureus ATCC 25923, respectively.

Cyanobacteria, an algae bloom that is responsible for the creation of deadly toxins. These toxins have the potential to adversely impact human and animal health. Microcystins (MC’s), are harmful toxins that are produced by cyanobacteria species. These deadly toxins are the most investigated toxins worldwide. However, in South Africa their occurrence statistics are deficient due to inaccessibility of reliable, sensitive, and precise analytical methods to investigate them in water surfaces. Thus, a development of analytical methods for the detection and accurate quantification of algal toxins is crucial to consider the health risk of exposure to toxins in wastewater and surface waters. This study recommends an analytical method for the detection and quantification of algal toxins using solid phase extraction (SPE) and high-performance liquid chromatography (HPLC) coupled with photodiode detector (PDA). The developed method was validated based on linearity which ranged from 3–2500 µg L− 1, recoveries at 99.6–113.9%, the limit of detection (LOD) ranging from 0.2–480 µg L− 1, and limit of quantification (LOQ) at 0.7–160 µg L− 1 and the regression coefficients obtained were above 0.9880 in all analytes. The developed method was applied to Darvill Wastewater Treatment Plant, Umgeni water, Durban surface waters, University of KwaZulu-Natal (UKZN) sport centre tap water and UKZN Westville two ponds), South Africa. MC-RR was the most detected analyte at concentration ranging from 0.069–30.521 ng L− 1 compared to other targeted MCs. The developed method is simple and cheap, which can consent developing countries to monitor these deadly MC toxins in water surfaces.