# Schiff Bases: Interesting Scaffolds with Promising Antitumoral Properties
## 2 Schiff Bases as Antiproliferative Agents
### Mono-Schiff Bases
[PERSON] et al. (2010) [48] studied several Schiff bases and tested their cytotoxic activity by the brine shrimp lethality assay. Medium lethal concentration (LD\({}_{50}\)) values for compounds **10** and **11** were 292.95 and 18.22 ppm, respectively. [PERSON] et al. (2010) [49] studied eight Schiff bases and evaluated their antiproliferative effects on human hepatoma HepG2 cells by sulforhodamine B assay. Compounds **12** and **13** were comparable to positive control, etoposide, showing IC\({}_{50}\) values of 5.6 and 6.8 \(\upmu\)M, respectively, versus 4.1 \(\upmu\)M of etoposide. [PERSON] et al. (2010) [50] studied two Schiff bases, PHP [\(N\)-(1-phenyl-2-hydroxy-2-phenylethylamine)-2-hydroxylphenylimine, **14**) and PHP [\(N\)-(2-hydroxybenzylidine)-2-hydroxylphenylimine, **15**) as anticancer agents acting on Ehrlich ascites carcinoma (EAC) cells in Swiss albino mice. All compounds were more active than standard anticancer drug, bleomycin, in improving the life span, lowering tumor weight, and inhibiting the tumor cell growth of EAC cell-bearing mice. The toxicity of the tested compounds was evaluated by measuring LD\({}_{50}\) values that were of 16 and 15.5 mg/kg for **14** and **15**, respectively. The maximum percentage cell growth inhibition of 93% was observed with **15** with dose loading of 2 mg/kg. [PERSON] et al. (2011) [51] studied a Schiff base derived from 2-aminobenzzothiazole and 2-thiophenencarboxaldehyde (**16**) for its antiproliferative activity against five human cancer cell lines (cervical carcinoma, HeLa; breast carcinoma, MCF-7; liver carcinoma, HepG2; colon carcinoma, HCT-116; and larynx carcinoma, HEP2). Compound **16** showed activity against HeLa cancer cells (IC\({}_{50}\) = T0.186 \(\upmu\)M). Moreover, its complexes with Cu(II), Fe(III), and Ni(II) showed a higher activity. [PERSON] et al. (2011) [52] prepared series of 14 imines and studied the suppression of proliferation of different human cancer cell lines (HeLa (cervical carcinoma), SW620 (colorectal adenocarcinoma, metastatic), MiaPaCa-2 (pancreatic carcinoma), MCF-7 (breast epithelial adenocarcinoma, metastatic)) and their cytotoxic activity on normal human fibroblasts (WI38 normal diploid human fibroblasts) using the MTT assay. Compounds **17** and **18** exerted a strong non-specific antiproliferative effect on all cell lines tested and a concentration-dependent effect on HeLa and MCF-7 cell lines at micromolar concentrations (IC\({}_{50}\) = 4.73 and 3.24 \(\upmu\)M on HeLa and 9.23 and 15.27 \(\upmu\)M on MCF-7). However, they were also highly cytotoxic on human fibroblasts. [PERSON] et al. (2011) [53] synthesized surfactants containing Schiff bases with hydrocarbon chains of different lengths (from C12 to C18). In vitro anticancer cytotoxic activity of these compounds was investigated using EAC as a model system of mice cell tumor at different concentrations (25, 50, and 100%) against liver carcinoma (HepG2), breast carcinoma (MCF-7), and colon carcinoma (HCT-116) cell lines. Compound **19**, bearing a C14 hydrocarbon chain, caused the death of 95% of EAC cell at the highest concentration. The IC\({}_{50}\) values for compound **19** at different concentrations ranged from 1 to 10 mg/mL. It showed high activity in in vitro system on the tumor cell lines investigated and the highest cytotoxic effect on HepG2, HCT-116, and MCF-7, respectively, and SBC12 surfactant-affected tumor tissue at very low concentrations at values lower than their critical micelle concentration (cmc) values. [PERSON] et al.