Eugenol β-Amino/β-Alkoxy Alcohols with Selective Anticancer Activity

Abstract

Eugenol, 4-allyl-2-methoxyphenol, is the main constituent of clove essential oil and has demonstrated relevant biological activity, namely anticancer activity. Aiming to increase this activity, we synthesized a series of eugenol β-amino alcohol and β-alkoxy alcohol derivatives, which were then tested against two human cancer cell lines, namely gastric adenocarcinoma cells (AGS) and lung adenocarcinoma cells (A549). An initial screening was performed to identify the most cytotoxic compounds. The results demonstrated that three β-amino alcohol derivatives had anticancer activity that justified subsequent studies, having been shown to trigger apoptosis. Importantly, the most potent molecules displayed no appreciable toxicity towards human noncancer cells. Structure-activity relationships show that changes in eugenol structure led to enhanced cytotoxic activity and can contribute to the future design of more potent and selective drugs.

Keywords: anticancer; apoptosis; cytotoxicity; eugenol; β-alkoxy alcohols; β-amino alcohols.

Figure 1

Viability of AGS cells exposed to the molecules at 200 μM (a) and 100 μM (b). The effect of topotecan at 5 μM is also presented in (b) for benchmark purposes. (c) Influence of molecule 5 (100 μM) on membrane integrity of AGS cells after 24 h. Triton X-100 at 1% was used as a positive control for maximum extracellular LDH activity. Each dot represents a single determination. C: control; T: topotecan. * p < 0.05; *** p < 0.001.

Figure 2

Viability of A549 cells exposed to the molecules at 200 μM (a) and 100 μM (b). The effect of topotecan at 5 μM is also presented in (b). (c) Influence of molecules 4 and 8 at 100 μM on membrane integrity of A549 cell line after 24 h. Triton X-100 at 1% was used as a positive control for maximum extracellular LDH activity. Each dot represents a single determination. C: control; T: topotecan. ** p < 0.01 *** p < 0.001.

Figure 3

Morphological assessment of AGS cells incubated with compound 5 (100 µM, 24 h). DNA was studied using DAPI and overall cell morphology with phalloidin.

Figure 4

Fold increase (normalized for DNA content) in caspase-3, -8, and -9 activation in (a) AGS with molecule 5 and (b) A549 with molecules 4 and 8. Topotecan at 2.5 μM was used as positive control. The values were normalized for DNA content; C: control; T: topotecan. * p < 0.05; ** p < 0.01; *** p < 0.001.

Figure 5

Viability of AGS cells exposed to molecule 5 at 100 μM combined with topotecan at 2.5 μM. Each dot represents a single determination. C: control; T: topotecan. *** p < 0.001.

Figure 6

Viability of AGS cells exposed to molecule 5 (100 μM) at 48 h/72 h and viability of A549 cells exposed to molecules 4 and 8 (100 μM) at 48 h/72 h. The results correspond to the mean value for at least three independent experiments performed in triplicate. Each dot represents a single determination. C: control; *** p < 0.001.

Figure 7

Chemical space occupied by the parent molecules 1 and 2 (blue dots) and β-amino (3–9, 14—orange dots)/β-alkoxy (10–13—green dots) alcohol derivatives. cLogP, calculated partition coefficient; TSA, total surface area; VDW, van der Waals surface.

Figure 8

Chemical structures of eugenol 1, epoxide 2, β-amino alcohols (3–9, 14) and β-alkoxy alcohols (10–13), obtained through different reactions between eugenol epoxide 2 and several amines or alcohols, respectively.