The use of betalains, which are nitrogenous plant pigments, by the food industry is widespread and reflects their safety after intake. The recent research showed outstanding results for L-tryptophan-betaxanthin, a phytochemical present in traditional Chinese medicine, as an antitumoral agent when the activity was evaluated in the animal model Caenorhabditis elegans. Thus, L-tryptophan-betaxanthin is now presented as a lead compound, from which eleven novel structurally related betaxanthins have been designed, biotechnologically produced, purified, and characterized. The antitumoral effect of the derived compounds was evaluated on the JK1466 tumoral strain of C. elegans. All the tested molecules significantly reduced the tumoral gonad sizes in a range between 31.4% and 43.0%. Among the novel compounds synthesized, tryptophan methyl ester-betaxanthin and tryptophan benzyl ester-betaxanthin, which are the first betalains to contain an ester group in their structures, caused tumor size reductions of 43.0% and 42.6%, respectively, after administration to the model animal. Since these were the two most effective molecules, their mechanism of action was investigated by microarray analysis. Differential gene expression analysis showed that tryptophan methyl ester-betaxanthin and tryptophan benzyl ester-betaxanthin were able to down-regulate the key genes of the mTOR pathway, such as daf-15 and rict-1.
Keywords: Caenorhabditis elegans; betaxanthins; cancer; phytochemicals; preclinical model; tryptophan.