Abstract
The reaction of 5-(3,4-dimethoxyphenyl)-1,3,4-oxadiazole-2(3H)-thione 3 with formaldehyde solution and primary aromatic amines or 1-substituted piperazines, in ethanol at room temperature yielded the corresponding N-Mannich bases 3-arylaminomethyl-5-(3,4-dimethoxyphenyl)-1,3,4-oxadiazole-2(3H)-thiones 4a–l or 3-[(4-substituted piperazin-1-yl)methyl]-5-(3,4-dimethoxyphenyl)-1,3,4-oxadiazole-2(3H)-thiones 5a–d, respectively. The in vitro inhibitory activity of compounds 4a–l and 5a–d was assessed against pathogenic Gram-positive, Gram-negative bacteria, and the yeast-like pathogenic fungus Candida albicans. The piperazinomethyl derivatives 5c and 5d displayed broad-spectrum antibacterial activities the minimal inhibitory concentration (MIC) 0.5–8 μg/mL) and compounds 4j, 4l, 5a, and 5b showed potent activity against the tested Gram-positive bacteria. In addition, the anti-proliferative activity of the compounds was evaluated against prostate cancer (PC3), human colorectal cancer (HCT-116), human hepatocellular carcinoma (HePG-2), human epithelioid carcinoma (HeLa), and human breast cancer (MCF7) cell lines. The optimum anti-proliferative activity was attained by compounds 4l, 5a, 5c, and 5d.
Highlights
The 1,3,4-Oxadiazoles are an important class of heterocyclic compounds with diverse pharmacological properties [1,2,3]
N-Mannich bases, we report the synthesis, characterization, antibacterial, antifungal, and anti-proliferative activities of related series of 5-(3,4-dimethoxyphenyl)-1,3,4oxadiazole-2(3H)-thione N-Mannich bases
The 3,4-Dimethoxybenzohydrazide 2 was prepared from the commercially-available methyl 3,4-dimethoxybenzoate 1 via treatment with hydrazine in ethanol [60]. 1,3,4Oxadiazole-2(3H)-thione 3 was obtained via reaction of the carbohydrazide 2 with carbon disulfide in ethanolic potassium hydroxide as previously described [61]
Summary
The 1,3,4-Oxadiazoles are an important class of heterocyclic compounds with diverse pharmacological properties [1,2,3]. There is a growing interest in the chemotherapeutic activities of 2,5disubstituted-1,3,4-oxadiazoles as antibacterial [10,11,12], antifungal [13,14,15], antitubercular [16,17], and antiviral [18,19,20,21] agents. 1,3,4-Oxadiazole-2(3H)-thiones, their thioether derivatives and 3-aminomethyl analogues (N-Mannich bases) are the most interesting for their anticancer activities [21,22]. 1,3,4-oxadiazole derivatives are highly attractive compounds in the development of organic light-emitting diodes (OLEDs) [45,46]
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