Benzo[h]quinoline derivatives are valuable scaffolds found in pharmaceuticals and natural products, known for their diverse biological activities and therapeutic potential. Acid hydrazides are versatile building blocks for synthesizing heterocyclic frameworks with enhanced pharmacological properties, including notable insecticidal activities [1]. Our research group has extensively explored the chemistry and bioactivity of these systems, highlighting their potential for developing new therapeutic and insecticidal agents [[2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17]]. Beyond their pharmaceutical significance, benzo[h]quinoline derivatives have also shown promising insecticidal properties. In our previous studies, we evaluated their larvicidal activity against Culex pipiens and found that several derivatives exhibited potent neurotoxic effects, disrupting key mosquito neuroreceptors and leading to high mortality rates [18,19]. Encouraged by these findings, we continue to explore their potential as effective mosquito control agents.

Controlling mosquito populations, particularly C. pipiens, remains a major public health priority. Culex pipiens serves as a primary vector for numerous debilitating and often fatal diseases. This species transmits arboviruses such as West Nile virus, St. Louis encephalitis virus, and Usutu virus, as well as filarial worms responsible for canine dirofilariasis [[20], [21], [22]]. Additionally, it contributes to the spread of avian malaria parasites [23] and has been implicated in transmitting harmful bacteria, including Bacillus anthracis, Staphylococcus warneri, and Bacillus cereus, which can contaminate raw milk and pose serious public health risks [24]. Given its significant role in disease transmission, the urgent need for effective and sustainable mosquito control strategies is evident.

Chemical insecticides have long been the primary means of controlling C. pipiens populations, but their extensive use has led to widespread insecticide resistance, complicating disease prevention efforts [[25], [26], [27], [28]]. Most insecticides target mosquito neuroreceptors, disrupting the nervous system and causing paralysis and death. Organophosphates, such as chlorpyrifos, act by inhibiting acetylcholinesterase (AChE), preventing the breakdown of acetylcholine, which leads to nerve overstimulation and insect paralysis [[29], [30], [31], [32]]. Neonicotinoids like nitenpyram function as agonists of nicotinic acetylcholine receptors (nAChRs), continuously stimulating them until the insect's nervous system is overwhelmed [[33], [34], [35]]. Oxadiazines, exemplified by indoxacarb, act as pro-insecticides, metabolizing into active forms that block voltage-gated sodium channels (VGSCs), disrupting nerve impulse transmission and leading to paralysis [36]. Additionally, insecticides such as fipronil target gamma-aminobutyric acid receptors (GABARs) by blocking GABA-gated chloride channels, preventing neural inhibition and causing nervous system hyperexcitation, ultimately resulting in insect death [37]. While these insecticides have been effective, their reliance on single-target mechanisms has contributed to resistance development, highlighting the need for novel multi-targeting approaches in mosquito control.

In our previously published studies, the insecticidal potential of benzo[h]quinoline derivatives was evaluated against C. pipiens larvae, demonstrating strong interactions with three key neuroreceptors: AChE, nAChRs, and VGSC, with AChE being predicted as the primary target of benzo[h]quinoline derivatives in these works (Fig. 1) [18,19]. This study advances beyond conventional insecticides, which typically act mainly on a single neuroreceptor, by designing benzo[h]quinoline derivatives capable of multi-receptor interactional strategy that remains underexplored for this scaffold. In this work, we expanded the structural diversity of benzo[h]quinoline derivatives by introducing new functional groups, broadening their neuro-targeting capability to include a fourth receptor, GABAR. These modifications aim to enhance multi-target interactions, improving insecticidal potency while reducing the likelihood of resistance emergence.

Computational analyses, including molecular docking, homology modeling, pharmacokinetic profiling, and molecular dynamics simulations, revealed that these modifications significantly increase receptor binding affinity, surpassing conventional insecticides in predicted stability and interaction strength. Unlike single-target insecticides, which are susceptible to resistance development through receptor mutations, our compounds simultaneously are predicted to inhibit AChE, overstimulate nAChRs, block VGSCs, and antagonize GABAR, leading to widespread synaptic disruption, neuromuscular impairment, and eventual paralysis in mosquito larvae. By rationally integrating functional elements from diverse insecticide classes into a multi-targeting benzo[h]quinoline framework, this study presents a novel strategy for developing next-generation insecticides with enhanced efficacy and improved resistance management, offering a sustainable approach to mosquito control.