title: Discovery of 6,7-dihydro-3H-pyrano[4,3-c]isoxazol-3-ones as a new class of pathogen specific anti-leptospiral agents.
abstract: A simple and efficient method for the synthesis of a series of 6,7-dihydro-3H-pyrano[4,3-c]isoxazol-3-one derivatives starting from 5-carboalkoxy-2,3-dihydropyranone (5-CDHPs) has been developed. Pyranoisoxazolones 10a-j, dihydronaphthopyran-4-one (DHNPs) class of natural product 12b and 12c and its analogues 12a and 13a-c were preliminarily screened against pathogenic leptospiral serovar Autumnalis strain N2 at various concentrations. Six pyranoisoxazolones, 10b, 10d, 10f, 10g, 10i and 10j which displayed very good anti-leptospiral activity was taken for secondary screening against twelve strains of pathogenic and one non-pathogenic leptospiral serovars. While all the compounds displayed significant anti-leptospiral activity against the pathogenic serovars at MIC of 62.5-500 μg/mL. Compounds 10d, 10g and 10j did not show any significant effect on non-pathogenic serovar. Inhibition of leptospires at a significant level by pyranoisoxazolone 10g was confirmed using RT-qPCR assay. In vivo treatment of BALB/c mice with compound 10g revealed that, it has 95% survivability against the pathogenic strain Canicola and also showed inhibition of renal colonization of leptospires. Compound 10g was found to show cytotoxicity against THP-1 cells only at higher concentration (≥75 μg/mL). Effective binding of compound 10g with leptospiral outer membrane protein LipL32 observed via in silico molecular docking provided a suitable explanation for pathogen specificity of compound 10g. Antibiotics acting against leptospirosis in human are very few. The results obtained from in vitro, in vivo and in silico study reveals that 6,7-dihydro-3H-pyrano[4,3-c]isoxazol-3-ones class of compounds are lead molecules for further development as pathogen specific anti-leptospiral agents.
authors.affiliation: School of Chemistry, Bharathidasan University, Tiruchirappalli, 620 024, Tamil Nadu, India. Electronic address: ilangovanbdu@yahoo.com.
authors.forename: Andivelu
authors.initials: A
authors.lastname: Ilangovan
authors.affiliation: School of Chemistry, Bharathidasan University, Tiruchirappalli, 620 024, Tamil Nadu, India.
authors.forename: Palaniappan
authors.initials: P
authors.lastname: Sakthivel
authors.affiliation: Medical Microbiology Laboratory, Department of Microbiology, School of Life Sciences, Bharathidasan University, Tiruchirappalli, Tamil Nadu, 620024, India.
authors.forename: Karikalacholan
authors.initials: K
authors.lastname: Sivasankari
authors.affiliation: Medical Microbiology Laboratory, Department of Microbiology, School of Life Sciences, Bharathidasan University, Tiruchirappalli, Tamil Nadu, 620024, India.
authors.forename: Charles Solomon Akino
authors.initials: CS
authors.lastname: Mercy
authors.affiliation: Medical Microbiology Laboratory, Department of Microbiology, School of Life Sciences, Bharathidasan University, Tiruchirappalli, Tamil Nadu, 620024, India.
authors.forename: Kalimuthusamy
authors.initials: K
authors.lastname: Natarajaseenivasan
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000138:chemical synthesis* / Q000494:pharmacology; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D055808:Drug Discovery; D006801:Humans; D007919:Leptospira / Q000187:drug effects*; D007922:Leptospirosis / Q000188:drug therapy; D008074:Lipoproteins / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D062105:Molecular Docking Simulation; D010080:Oxazoles / Q000138:chemical synthesis* / Q000494:pharmacology; D016019:Survival Analysis
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; C406589:LipL32 protein, Leptospira; D008074:Lipoproteins; D010080:Oxazoles
keywords: 5-Carboalkoxy-2,3-dihydropyranone; 6,7-Dihydro-3H-pyrano[4,3-c]isoxazol-3-one; Anti-leptospiral; LipL32; Pathogen-specific