title: Antioxidant and antimicrobial studies on fused-ring pyrazolones  and isoxazolones.
abstract: A series of 3-nitrochalcones have been synthesized enroute towards fused ring pyrazolones and isoxazolones. Base catalyzed condensation of the chalcones with ethylacetoacetate yielded cyclohexenones in good yields (74-76%). The treatment of cyclohexenones with hydrazine hydrate or hydroxylamine chloride in the presence of a base afforded the corresponding fused-ring pyrazolinones (70-78% yield) and isoxazolinones (58-66% yield). The newly synthesized compounds were characterized by IR, 1D and 2D NMR and HRMS spectral analysis. The compounds were screened for their antioxidant and antimicrobial activities. Pyrazolinones showed good DPPH radical scavenging and iron metal chelating properties. The para-hydroxy group was important for a compound to have enhanced antioxidant activity. Pyrazolinones and isoxazolinone exhibited a wider range of antimicrobial activities compared to cyclohexenones. Pyrazolinones and isoxazolinone bearing a thiophene ring were the most potent type of compounds against Bacillus subtilis and Candida albicans with MIC values of 0.313-1.25 μg/mL. Some of the synthesized compounds were found to have promising antioxidant, metal chelation and antimicrobial activities.
authors.affiliation: Botswana Institute for Technology Research and Innovation, Private Bag 0082, Gaborone, Botswana. Electronic address: mazimbaof@yahoo.com.
authors.forename: Ofentse
authors.initials: O
authors.lastname: Mazimba
authors.affiliation: Department of Biological Sciences, University of Botswana, Private Bag 00704, Gaborone, Botswana.
authors.forename: Kabo
authors.initials: K
authors.lastname: Wale
authors.affiliation: Department of Biological Sciences, University of Botswana, Private Bag 00704, Gaborone, Botswana.
authors.forename: Daniel
authors.initials: D
authors.lastname: Loeto
authors.affiliation: Department of Biological Sciences, University of Botswana, Private Bag 00704, Gaborone, Botswana.
authors.forename: Tebogo
authors.initials: T
authors.lastname: Kwape
mesh_terms: D000900:Anti-Bacterial Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D000935:Antifungal Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D000975:Antioxidants / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D001412:Bacillus subtilis / Q000187:drug effects*; D002176:Candida albicans / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D007555:Isoxazoles / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D047069:Pyrazolones / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D013329:Structure-Activity Relationship
chemical_list: D000900:Anti-Bacterial Agents; D000935:Antifungal Agents; D000975:Antioxidants; D007555:Isoxazoles; D047069:Pyrazolones