Changes in bioactive compounds and antioxidant activity of three Amaranthus L. genotypes from a model to household processing

Amaranthus L. leaves are consumed as vegetables and are a rich source of secondary plant metabolites. The phenolic profiles of the three analyzed genotypes by LC-Q-TOF-MS/MS and HPLC-DAD were characterized by high amounts of hydroxycinnamic glucaric and-isocitric acids. 'Gartenfuchsschwanz' (A. hybridus L.) and 'Red Callaloo' (A. tricolor L.) had similar profiles. 'Gemuse-Amaranth' (A. tricolor L.) had a high amount of caf-feoylglucaric acid 4, which was isolated, and afterward identified by NMR. Its antioxidant activity, measured by TEAC, DPPH, and TPC, was similar to 5-caffeoylquinic acid, common in many plant species. The antioxidant activity of Amaranthus L. can be explained rather by their different phenolic-and ascorbic acid concentrations than by their species. Household cooking reduces antioxidant activity due to oxidation processes while leaching into cooking water could be neglected. Amaranthus L. baked into a wheat-dough-matrix showed lower phenolic concentrations, presumably due to the formation of phenol-protein-bounds and thermal degradation.

Automated summary

Amaranthus L. leaves are rich in secondary plant metabolites, with high amounts of hydroxycinnamic glucaric and-isocitric acids. They also exhibit antioxidant activity similar to 5-caffeoylquinic acid. The antioxidant activity is influenced more by the phenolic and ascorbic acid concentrations rather than the species of Amaranthus L. Household cooking may reduce antioxidant activity, while leaching into cooking water has negligible effects. Baking Amaranthus L. into a wheat-dough-matrix may result in lower phenolic concentrations due to phenol-protein binding and thermal degradation.