Abstract
A new series of chalcones (4a-c) and allylicchalcones (11a-b) have been prepared by the Claisen-Schmidt condensation. A novel series of pyrazolicchalcones (5a-c) have been synthesized by the reaction of respective chalcones (4a-c) and hydrazine hydrate. The structures of the compounds were confirmed by spectral data (infrared spectroscopy and 1H nuclear magnetic resonance). All of the compounds (4/5a-c and 11a-b) have been tested for their antimicrobial activities (agar disc-diffusion method) and antioxidant activities (1,1-biphenyl-2-picrylhydrazyl free radical scavenging method). The test compounds failed to show antibacterial properties (4a-c, 5b, and 11a-b) or exhibited such properties poorly (5a and 5c). None of the test compounds displayed antifungal properties. Of the compounds tested, compounds 5a-c and 11a-b exhibited promising antioxidant activities.
Highlights
Flavonoids comprise a large family of plant-derived polyphenolic compounds classified as anthocyanidins, flavonols, chalcones, aurones, flavanones, isoflavones, flavans, flavanonols, flavanols, and flavones differencing from each other in their structural group arrangements [1]
We have synthesized a series of chalcones 4a-c, pyrazolicchalcones 5a-c and allylicchalcones 11a-b with appropriate nucleophiles using the procedures presented in Schemes 1 and 2
The results indicated that compounds 4a-c, 5b and 11a-b did not exhibit antibacterial properties whereas compounds 5a and 5c displayed poor antibacterial activity towards Gram-positive bacteria showing inhibitor zones between 10 and 16 mm and minimum inhibitor concentrations (MICs) values higher than 256 μg/ml for Streptococcus faecalis and 512 μg/ml for Methicillin-sensitive Staphylococcus aureus (MSSA) and Methicillin-resistant Staphylococcus aureus (MRSA) compared to Sulfamethoxazole
Summary
Flavonoids comprise a large family of plant-derived polyphenolic compounds classified as anthocyanidins, flavonols, chalcones, aurones, flavanones, isoflavones, flavans, flavanonols, flavanols, and flavones differencing from each other in their structural group arrangements [1]. Antioxidants are the compounds that prevent such oxidative damage due to their free radical scavenging ability [5] In chalcones, such ability is attributable to phenolic-OH group attached to the ring structure [6]. Chalcones with antioxidant activity (and compounds with such activity in general) have been demonstrated to have anticancer, anticardiovascular, anti-inflammatory, and many other activeties [7,8]. The presence of enone function in chalcones having pyrazole moiety has been found to enhance the biological activity [13] Prompted by all these observations, we report the synthesis, antioxidant and antimicrobial activities of novel chalcones, pyrazolicchalcones and allylicchalcones
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