Pharmacological evaluation of ONNO donor quadridentate Schiff bases

Abstract

Four ONNO donor Schiff bases 2-((E)-(2-((E)-2-hydroxybenzylideneamino)ethylimino) methyl)phenol (H₂L₁), 2-((E)-(2-((E)-2-hydroxybenzylideneamino)propylimino)methyl) phenol (H₂L₂), 2-((E)-1-(2-((E)-1-(2-hydroxyphenyl) ethylideneamino)ethylimino)ethyl) phenol (H₂L₃) and 2-((E)-1-(2-((E)-1-(2-hydroxyphenyl)ethylideneamino)propylimino) ethyl)phenol (H₂L₄) were synthesized by the reactions of ethylene/propylene diamines with 2-hydroxy benzaldehyde/2-hydroxy acetophenone. The new compounds were characterized by FT-IR and NMR (¹H and ¹³C) spectroscopic techniques accompanied by elemental, GC/MS and single crystal X-ray diffraction analyses. These compounds were screened for various biological studies i.e. brine shrimp cytotoxic, antitumor and antibacterial activities The compound H₂L₃ showed highest cytotoxic and antitumor activities with lowest LD₅₀ (14.27) and IC₅₀ values (18.90). All the compounds were highly active in protecting DNA against hydroxyl free radicals. Antibacterial studies had shown that these were inactive against Gram positive bacteria (Staphylococcus aureus and Micrococcus luteus) while active against Gram negative bacteria (Enterobacter aerogenes, Bordetella bronchiseptica and Salmonella typhi) showing variable antibacterial activity.