Pseudomonas aeruginosa biofilm formation is critical to antibiotic resistance and persistence. Targeting cyclic di-GMP (c-di-GMP) signaling, a master biofilm formation and virulence regulator, presents a promising strategy to combat resistant bacterial infections. Myricetin, a natural polyphenolic flavonoid with documented antimicrobial and anti-biofilm activities, may enhance antibiotic efficacy against Pseudomonas aeruginosa. This study evaluated the synergistic effects of myricetin combined with azithromycin, ciprofloxacin, or cefdinir against both standard and drug-resistant Pseudomonas aeruginosa strains. Antibacterial activity, biofilm disruption, and motility inhibition were experimentally assessed, while molecular dynamic (MD) simulations elucidated myricetin’s molecular mechanism of action. Our results suggested that myricetin synergistically potentiated all three antibiotics, reducing c-di-GMP synthesis by 28% (azithromycin), 57% (ciprofloxacin), and 30% (cefdinir). It enhanced bactericidal effects, suppressed biofilm formation, and impaired swimming, swarming, and twitching motility. Computational analyses revealed that myricetin binds allosterically to FimX very well, a key regulator in the c-di-GMP signaling pathway. Hence, myricetin may act as a c-di-GMP inhibitor, reversing biofilm-mediated resistance in Pseudomonas aeruginosa and augmenting antibiotic efficacy. This integrated experimental and computational approach provides a framework for developing anti-virulence and antibiotic combination therapies against recalcitrant Gram-negative pathogens.

Urinary tract infections (UTIs), primarily caused by uropathogenic Escherichia coli (UPEC), have high morbidity and recurrence rates. Resistance to levofloxacin hydrochloride (LEV), a commonly used treatment for UTIs, is increasingly problematic, exacerbated by biofilm formation mediated by interactions between cyclic di-GMP (c-di-GMP or CDG) and YcgR. In this study, we identified three caffeoylquinic acid compounds from Pyrrosia lingua—chlorogenic acid (CGA), sibiricose A5 (Si-A5), and 3-O-caffeoylquinic acid methyl ester (CAM)—that target YcgR through molecular docking. Biological assays revealed that combining these compounds with levofloxacin hydrochloride significantly enhanced antibacterial activity against standard UPEC strains in a concentration-dependent manner and clinically isolated UPEC strains. Notably, chlorogenic acid and sibiricose A5, when used with levofloxacin hydrochloride, enhanced intracellular c-di-GMP levels and swimming motility, significantly reduced YcgR gene expression, and effectively inhibited biofilm formation of UPEC at multiple time points. Additionally, molecular dynamics simulations elucidated the strong binding of these compounds to YcgR, underscoring the critical roles of residues, such as Arg118 and Asp145. This research serves as a foundation for tackling antibiotic resistance and developing innovative therapeutics for UTIs.

Barbatic acid, a compound isolated from lichen, has demonstrated a variety of biological activities. In this study, a series of esters based on barbatic acid (6a–q′) were designed, synthesized, and evaluated for their diuretic and litholytic activity at a concentration of 100 μmol/L in vitro. All target compounds were characterized using ¹H NMR, ¹³C NMR, and HRMS, and the spatial structure of compound 6w was confirmed using X-ray crystallography. The biological results showed that some derivatives, including 6c, 6b′, and 6f′, exhibited potent diuretic activity, and 6j and 6m displayed promising litholytic activity. Molecular docking studies further suggested that 6b′ had an optimal binding affinity to WNK1 kinases related to diuresis, while 6j could bind to the bicarbonate transporter CaSR through a variety of forces. These findings indicate that some barbatic acid derivatives could be further developed into novel diuretic agents.

A simple and efficient hydroxide-mediated S_NAr rearrangement was reported to synthesize new depside derivatives containing the diaryl ether skeleton from the natural product barbatic acid. The prepared compounds were determined using ¹H NMR, ¹³C NMR, HRMS, and X-ray crystallographic analysis and were also screened in vitro for cytotoxicity against three cancer cell lines and one normal cell line. The evaluation results showed that compound 3b possessed the best antiproliferative activity against liver cancer HepG2 cell line and low toxicity, which made it worth further study.

Against the backdrop of rising multidrug-resistant Acinetobacter baumannii (MDR AB) threats, this study explores the in vitro antibacterial activity and mechanism of Senecio scandens (a Miao ethnic medicinal herb) crude extract. Using 10 clinical MDR AB strains, we reassessed antibiotic sensitivity and then applied microbroth dilution to determine MIC/MBC, time-kill curves for bactericidal kinetics, and SEM/TEM for structural changes. Proteomics identified downregulated proteins, cross-referenced with VFDB/CARD to target membrane-related proteins (msbA, lptD), while molecular docking validated the strong binding of linarin/hyperoside to these targets. qPCR confirmed lptD/msbA mRNA downregulation (p < 0.05) by linarin/hyperoside (MIC = 312.5 μmol/L). The extract showed concentration-dependent bactericidal effects (MIC = 640 μg/mL), disrupting cell wall/membrane integrity. This study first reveals that linarin and hyperoside inhibit MDR AB by downregulating lptD/msbA, compromising outer membrane integrity, offering novel therapeutic candidates.