Novel Aminonaphthoquinone Mannich Bases Derived from Lawsone and their Copper(II) Complexes: Synthesis, Characterization and Antibacterial Activity

• Published in: Journal of the Brazilian Chemical Society Vol. 20; no. 4; pp. 712 - 727
• Main Authors: Neves, Amanda P., Barbosa, Claudia C., Greco, Sandro J., Vargas, Maria D., Visentin, Lorenzo C., Pinheiro, Carlos B., Mangrich, Antonio S., Barbosa, Jussara P., da Costa, Gisela L.
• Format: Journal Article
• Language: English
• Published: SAO PAULO Soc Brasileira Quimica 01.01.2009; Sociedade Brasileira de Química
• Subjects: Chemistry; CHEMISTRY, MULTIDISCIPLINARY; Physical Sciences; Science & Technology; antibacterial activity; SERIES; CRYSTAL-STRUCTURE; aminonaphthoquinones; MOLLUSCICIDAL ACTIVITY; NAPHTHOQUINONES; POTENT; copper complexes; AGENTS; Mannich bases; crystal structure determination; ANTIFUNGAL; DERIVATIVES; CYTOTOXICITY; ANTIMICROBIAL ACTIVITY
• ISSN: 0103-5053; 1678-4790; 1678-4790
• DOI: 10.1590/S0103-50532009000400015

A series of novel Mannich bases (HL1-HL13) derived from 2-hydroxy-1,4-naphthoquinone (lawsone), substituted benzaldehydes [(C6H2RRRC)-R-1-R-2-C-3(O)H] and various primary amines (NH2R4, R-4 = n-butyl, benzyl, allyl, 2-furfuryl), and their Cu2+ complexes, [Cu(L1)(2)]-[Cu(L13)(2)], have been synthesized and fully characterized by analytical and spectroscopic methods. The structures of complexes 1 (R-1 = R-2 = R-3 = H; R-4 = Bu), 2 (R-1 = R-3 = H; R-2 = NO2; R-4= Bu) and 7 (R-1 = OH; R-2 = R-3 = H; R-4= Bu) were determined by single crystal X-ray diffraction studies. All complexes crystallize in centrosymmetric space groups, with a copper atom in the inversion centre. Two L- coordinate through the naphthalen-2-olate oxygen and secondary amine-N atoms, forming six-membered chelate rings around the copper atom in a trans-N2O2 environment; spectroscopic data confirm that the other complexes exhibit similar molecular arrangement. The antimicrobial activity of all compounds has been tested on seven different strains of bacteria: Bacillus cereus, Bacillus subtilis, Escherichia coli, Enterococcus faecalis, Klebsiella pneumoniae, Pseudomonas aeruginosa and Staphylococcus aureus. In general, Mannich bases were more active than complexes, HL11 (R-1 = OH; R-2 = H; R-3 = Me; R-4= Bn) and HL13 (R-1 = OH; R-2 = H; R-3 = Br; R-4 = Bn) being the most potent inhibitors. The MIC for the most active compound HL11 against S. Coli was 20 mu mol L-1 (8 mu g mL(-1)), better than Chloramphenicol (90 mu mol L-1) and well below most values reported for other naphthoquinones.