Antimicrobial activity of natural quinone-methide triterpenoids celastrol and pristimerin against pathogenic <i>Neisseria</i>

<i>Neisseria gonorrhoeae</i> and <i>Neisseria meningitidis</i> are closely related and important human pathogens that cause distinct diseases of clinical significance. While <i>N. meningitidis</i> infrequently demonstrates antibiotic resistance, the rapid emergence of multidrug-resistant <i>N. gonorrhoeae</i> isolates emphasizes the urgency of novel therapeutics against this pathogen. Recently, repurposing of approved drugs and the therapeutic potential of natural compounds have been explored as alternative strategies to treat gonococcal infections. We screened 54 natural bioactive compounds and identified celastrol and pristimerin, two quinone-methide triterpenoids, which exhibited bactericidal activity against <i>N. gonorrhoeae</i> 1291. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for 10 susceptible and multidrug-resistant <i>N. gonorrhoeae</i> strains ranged between 0.4-11.3 mg/L and 0.7-23.3 mg/L, respectively. Both compounds were also bactericidal against a diverse panel of <i>N. meningitidis</i> strains representing multiple serogroups. The MIC and MBC for <i>N. meningitidis</i> strains ranged between 1.4-23.3 mg/L and 1.4-46.5 mg/L, respectively. Pristimerin effectively cleared <i>N. gonorrhoeae</i> infection in transformed primary cervical epithelial cells without inducing cytotoxicity at biologically active concentrations. In contrast, celastrol exhibited a modest cytotoxic effect on the cells. In summary, we screened a library of bioactive compounds and identified the natural quinone-methide triterpenoids celastrol and pristimerin, as antimicrobial leads against pathogenic <i>Neisseria</i> species. These compounds represent promising scaffolds for the future development of therapeutics targeting gonorrhea.IMPORTANCE<i>Neisseria gonorrhoeae</i> and <i>Neisseria meningitidis</i> cause clinically significant diseases, but rising multidrug-resistant <i>N. gonorrhoeae</i> creates an urgent need for new therapies. We screened 54 natural bioactive compounds from the NatureBank library and identified celastrol and pristimerin, two quinone-methide triterpenoids with notable bactericidal activity against susceptible and resistant <i>N. gonorrhoeae</i>, as well as diverse <i>N. meningitidis</i> serogroups. Celastrol showed stronger activity but limited selectivity and known toxicity, indicating a need for structural optimization. Pristimerin exhibited a favorable safety margin while maintaining antimicrobial potency. These findings highlight natural triterpenoids as promising scaffolds for lead optimization and development into novel antimicrobials to combat antibiotic-resistant gonorrhea.