Hydroquinine

Hydroquinine (Dihydroquinine) is an anti-bacterial agent that inhibits both Gram-positive and Gram-negative bacteria. Hydroquinine inhibits the growth of multidrug-resistant pseudomonas aeruginosa via the suppression of the arginine deiminase pathway genes. Hydroquinine inhibits Plasmodium falciparum and Plasmodium berghei. Hydroquinine displays anti-malarial and demelanizing activities. Hydroquinine effectively induces specific RND-type efflux pump systems in Pseudomonas aeruginosa, particularly the MexCD-OprJ and MexXY efflux pumps. Hydroquinine inhibits Pseudomonas aeruginosa adhesion and biofilm formation. Hydroquinine serves as a precursor for derivatives such as C9 epihydroquinine, 9-acetoxy-10,11-dihydroquinine, and 10,11-dihydroquinine monohydrochloride^[1][2][3]. In Vitro:Hydroquinine (0.25-10 mg/mL, 16-20 h) inhibits and kills gram-positive and gram-negative bacteria (PA-27853, PA-S1, PA-S2, PA-S3, PA-S4, PA-S5, PA-S6, S. aureus ATCC25923, S. aureus ATCC29213, E. cloacae ATCC2341, E. coli ATCC2452, E. coli ATCC25922, K. pneumoniae ATCC1705, P. aeruginosa ATCC BAA-2108 and P. aeruginosa ATCC27853) at minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 1.25 and 5.00 mg/mL, respectively^[1][2].
Hydroquinine (16-20 h) shows notable partial synergistic effects with Ceftazidime (HY-B0593) (fractional inhibitory concentration index (∑FICI) of 0.750 and 0.625 against clinical MDR P. aeruginosa strains PA-S4 and PA-S5, respectively)^[1].
Hydroquinine (1.25-1.5 mg/mL, 1 h) inhibits P. aeruginosa growth through decreased expression of ADI-pathway related genes and decreased expression levels of adhesion-related genes^[1][3].
Hydroquinine (0.625-5 mg/mL, 0-8 h) kills P. aeruginosa ATCC27853 and ATCC BAA-2108, achieving 20-40% killing at 0.5 × MIC, approximately 50% at MIC, and 90% at MBC after 4 hours^[2].
Hydroquinine (1.25 mg/mL, 1 h) significantly upregulates RND-type efflux pump genes in P. aeruginosa ATCC27853^[2].
Hydroquinine (1.25-2.5 mg/mL, 6-24 h) exhibits inhibitory activity comparable to multipurpose solutions (MPSs) and, in combination, damages cell structure while demonstrating anti-adhesion efficacy^[3].
Hydroquinine (0-50 µM, 24-72 h) inhibits Toxoplasma gondii RH-RFP tachyzoite growth, with IC₅₀ values of 0.63, 0.68, and 0.0014 µM after 24, 48, and 72 hours, respectively^[4].
Hydroquinine (6.25-50 µM) inhibits tachyzoite infection and replication in a dose-dependent manner, reducing parasitophorous vacuole (PV) formation at 6.25 µM and further decreasing tachyzoite replication at 50 µM^[4].
Hydroquinine (6.25-50 µM, 105 min) induces reactive oxygen species generation in Toxoplasma gondii^[4].
Hydroquinine (6.25-50 µM, 8 h) causes mitochondrial membrane damage in Toxoplasma gondii but not of the host cells^[4].