Synthesis of new quaternized chitosan Schiff bases and their N-alkyl derivatives as antimicrobial and anti-biofilm retardants in membrane technology.

New quaternized salicylidene chitosan Schiff bases (QSCSBs) and their N-octyl derivatives (OQCs) have been synthesized and characterized, aiming to develop innovative antimicrobial and anti-biofilm agents. This research holds immense potential, as these compounds could be utilized as anti-biofouling additives in membrane technology in the future. The synthesis involved the modification of low molecular-weight-chitosan (LMC) through simultaneous Schiff base formation and quaternization processes to create QSCSBs. Subsequently, QSCSBs were catalytically reduced to form quaternized N-benzyl chitosan (QBCs) intermediates, which then underwent nucleophilic substitution reactions affording N-octyl quaternized chitosans (OQCs). Characterization techniques such as elemental, spectral, and microscopic analyses were used to confirm the successful synthesis of these materials. As membrane technology relies on surface charge, QSCSBs and OQCs with large zeta potentials could be used as positively charged additives. Moreover, SEM image revealed the regular distribution of pores and voids across the additives' surfaces raises intriguing questions about their implications for membrane performance. Meanwhile, the superior antibacterial and antibiofilm potential of these materials, particularly QSCSB2 and OQC2, indicate that the utilization of these compounds as anti-biofouling additives in membrane technology could significantly improve the performance and longevity of membranes used in various applications such as water treatment and desalination.

Design, synthesis, anti-inflammatory evaluation, and molecular modelling of new coumarin-based analogs combined curcumin and other heterocycles as potential TNF-α production inhibitors via upregulating Nrf2/HO-1, downregulating AKT/mTOR signalling pathways and downregulating NF-κB in LPS induced macrophages.

Persistent inflammation contributes to various inflammatory conditions. Inflammation-related diseases may be treated by inhibiting pro-inflammatory mediators and cytokines. Curcumin and coumarin derivatives can target signalling pathways and cellular factors to address immune-related and inflammatory ailments. This study involved designing and synthesising three series of coumarin-based analogs that incorporated curcumin and other heterocycles. These analogs were evaluated for their potential as anti-inflammatory agents in LPS-induced macrophages. Among the fourteen synthesised coumarin derivatives, compound 14b, which contained 3,4-dimethoxybenzylidene hydrazinyl, demonstrated the highest anti-inflammatory activity with an EC50 value of 5.32 µM. The anti-inflammatory effects of 14b were achieved by modulating signalling pathways like AKT/mTOR and Nrf2/HO-1, and downregulating NF-kß, resulting in reduced production of pro-inflammatory cytokines such as IL-6, IL-1ß, and TNF-α. The modelling studies revealed that 14b and dexamethasone bind to the same TNF-α pocket, suggesting that 14b has potential as a therapeutic agent superior to dexamethasone for TNF-α.

Three series of curcumin-based analogs, incorporating other heterocycles, were synthesised with the intention of exploring their potential as anti-inflammatory agents.Subsequently, these analogs underwent biological assessment in macrophages induced by LPS to determine their anti-inflammatory efficacy.Among the fourteen coumarin derivatives synthesised, the most potent anti-inflammatory activity was observed in the coumarin compound 14b, which featured a 3,4-dimethoxybenzylidene hydrazinyl moiety, with an EC₅₀ value of 5.32 µM.The anti-inflammatory effects of compound 14b were achieved through the modulation of signalling pathways such as AKT/mTOR and Nrf2/HO-1, as well as the downregulation of NF-kß, resulting in decreased production of pro-inflammatory cytokines including IL-6, IL-1ß, and TNF-α.Molecular modelling studies revealed that both compound 14b and dexamethasone bind to the same binding site on TNF-α, suggesting that 14b has the potential to serve as a therapeutic agent for TNF-α and other pro-inflammatory cytokines that surpasses that of dexamethasone.