A series of isoxazole based (E)-1-(isoxazole-5-yl)-3-(substituted phenyl)-prop-2-en-1-ones (chalcones, 3a-3o) and 3-(isoxazol-5-yl)-5-(substituted phenyl)-4,5-dihydro-1H-pyrazole-1-carboxamide (dihydropyrazoles, 4a-4o) were synthesized, characterized and evaluated for their antimicrobial, antioxidant and anticancer properties. Chalcones exhibited excellent antibacterial and antioxidant activities whereas the dihydropyrazoles shown superior antifungal and anticancer activities. The compound 3l containing 3,4,5-trimethoxy phenyl ring showed the potent antibacterial activity (MIC = 1 µg/mL) as well as the antioxidant activity (IC50 = 5 µg/mL) whereas the dihydropyrazole, 4o (MIC = 0.5 µg/mL) bearing the 2-chloro-3,4-dimethoxyphenyl was the potent antifungal compound identified. The dihydropyrazoles 4n and 4h possessing 2-fluoro-3,4-dimethoxyphenyl and 3,4-dimethoxyphenyl substituents exhibited potent anticancer activity against prostate cancer cell line (DU-145) with MIC 2 and 4 µg/mL respectively. The structure activity relationships had shown that there is a marked influence of both electron withdrawing halogens and electron releasing methoxyl groups on the above biological activities. All the compounds were evaluated for toxicity on normal human cell lines (LO2) and found to be non-toxic. These studies could help to synthesize, explore and identify new isoxazole containing leads for antimicrobial, antioxidant and anticancer properties.
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