Synthesis and evaluation of antimicrobial and cytotoxic activities of some Mannich bases bearing amino acid units and their copper complexes

A series of Mannich bases, namely, N-(2-hydroxynaphthalen-1-ylmethyl)-L-amino acids (ligands, I-VII) have been prepared from condensation reaction of 2-naphthol with the proper amino acids including glycine, alanine, valine, leucine, methionine, phenylalanine, and tyrosine in the presence of formaldehyde. The corresponding copper (II) complexes (VIII-XIV) have been synthesized and obtained in a moderate yields. The structures of all new products were confirmed by elemental analyses of C, H, N and spectroscopic methods. All compounds were screened for their antimicrobial activity against some Gram- positive bacteria: Staphylococcus aureus (ATCC 25923) and Micrococcus luteus (ATCC 6635), Gram – negative bacteria: Pseudomonas fluorescens (S 97) and Salmonella typhimurium (ATCC 14028), Yeast: Candida albicans (ATCC 10231) and Fungus: Aspergillus fumigatus. The comparison of antimicrobial activities of the ligands and complexes proved that the presence of copper metal causes more inhibition i.e., more activity, especially against Staphylococcus aureus and Candida albicans. The cytotoxic activity of selected two copper complexes was also evaluated against the Mammalian cell line: HEpG2.