The misuse of antibiotics has led to a range of health issues associated with resistant bacterial infections worldwide [1]. Moreover, some Gram-positive bacteria exhibit invasive properties and then activate intracellular survival ability, conferring resistance to antibiotic-induced eradication [[2], [3], [4]]. These internalized bacteria even exploit hijacking the defence response of host cells to enhance their survival [5,6]. Consequently, the antimicrobial actions of natural products that focus on host responses are expected to be leveraged in the battle against internalized bacteria [7,8]. Several plant-derived natural therapeutics exhibit multitarget antibacterial properties, including the ability to enhance host immune response [9] and maintain normal cellular functions [10]. Flavonols are extensively distributed among plant natural products [11], with the chemical structures of over 8000 flavonoids having been elucidated [12,13]. A majority of currently known flavonols display a broad spectrum of antimicrobial effects and the capacity to modulate host cell signalling pathways [14,15]. Within this group, flavonols constitute a distinct subclass of flavonoids distinguished by specific chemical structures and biological activities. The fundamental structure of flavonols comprises two benzene rings (designated as A and B rings) linked by a central three-carbon atom, with attached phenolic hydroxyl groups. The core parent nucleus is identified as 2-phenylchromogenone [8,16]. These flavonol compounds exhibit a remarkable diversity of biological activities, encompassing antibacterial, anti-inflammatory, and antioxidant properties [3,17]. In particular, flavonols play a pivotal role in the modulation of host-directed antibacterial therapy [18,19]. However, the precise host targets and mechanisms underlying their pharmacological action remain to be elucidated.

In an effort to investigate the host-directed antibacterial actions of flavonols against internalized bacteria, we found that three flavonols (myricetin, kaempferol, and quercetin) significantly reduced the intracellular colonization of internalized bacteria. Subsequently, we conducted a combined approach utilizing network pharmacology and transcriptomics to unveil the potential targets of these flavonols. Our findings show that flavonols mitigate membrane damage and inhibit apoptotic cell death caused by internalized bacteria. Notably, myricetin, characterized by its numerous phenolic hydroxyl groups, showed pronounced inhibitory effects on both reactive oxygen species (ROS) generation and mitochondrial membrane potential (ΔΨm) impairment. Furthermore, our results suggest that flavonols attenuate apoptotic cell death through modulation of PI3K/Bcl-2 and the activation of caspase-9/caspase-3. Ultimately, myricetin increased the ability of glutathione (GSH) and glutathione peroxidase (GSH-Px) while inhibiting caspase-3 activation in vivo. Our findings identify potential targets of flavonols as host-directing antibacterial agents that can counteract drug resistance and persistence resulting from the increased survival of internalized bacteria.