An efficient one-pot synthesis of polyphenolic amino acids and evaluation of their radical-scavenging activity

Protective effect of olive oil polyphenol phase II sulfate conjugates on erythrocyte oxidative-induced hemolysis

The consumption of extra virgin olive oil (EVOO) has been associated with a lower incidence of cardiovascular diseases partly due to its polyphenol content. The metabolites hydroxytyrosol sulfate and hydroxytyrosol acetate sulfate were shown to be the most concentrated polyphenol metabolites found in plasma after EVOO consumption. Therefore, the capacity of hydroxytyrosol, hydroxytyrosol acetate, homovanillyl alcohol, homovanillyl alcohol acetate and tyrosol sulfate metabolites, to protect red blood cells (RBCs) from oxidative injury induced by the radical initiator 2,2'-azo-bis(2-amidinopropane) dihydrochloride (AAPH) was evaluated. In the presence of AAPH, all non-sulfated compounds and the hydroxytyrosol and hydroxytyrosol acetate monosulfate metabolites showed a significant protective activity against RBCs induced oxidative hemolysis. Moreover, even at 5 μM, the protection was highly significant for hydroxytyrosol acetate, hydroxytyrosol and hydroxytyrosol acetate 3' and 4' monosulfates. The morphological changes of RBC and the nature of their hemoglobin were in accordance with the hemolysis assay. Results showed that a free phenolic hydroxyl group is needed for the antioxidant protection given by compounds. Hydroxytyrosol metabolites present as phase II sulfate conjugates are actually able to protect RBC from oxidative injury by a non-transcriptional mechanism and are likely to contribute for the anti-atherosclerosis properties of regular EVOO consumption.

Multicomponent Reactions for Integrating Multiple Functional Groups into an Antioxidant

A large number of convincing evidences has revealed the correlation of the pathogeny of diseases with the oxidative damages of DNA, protein, biomembrane, and other biological species, while supplementation of antioxidants is demonstrated to be a promising way to avoid, at least, rectify the unbalance redox status in vivo. Although many endeavors have focused on synthesis of antioxidants, a main hurdle still hinders the wide usages of synthetic antioxidants because of low bioavailability and potential cytotoxicity. The search for antioxidants with multiple functional groups being recognized by different receptors becomes a much sought by researchers, and multicomponent reactions (MCRs) provide with powerful tools for the construction of multifunctional antioxidants. Presented herein is a personal account on the application of MCRs for the synthesis of multifunctional antioxidants, while radical-induced oxidation of DNA acts as the experimental system for evaluating antioxidative effect. Concretely, the Biginelli three-component reaction (3CR) affords such a dihydropyrimidine scaffold that the tautomerization between C=S and C-SH leads to antioxidative effect. The Povarov 3CR is able to integrate multiple antioxidative groups, i. e., ferrocenyl and -N(CH₃ )₂ , into a quinoline scaffold, while the Groebke 3CR provides with imidazo[1,2-a]pyridine skeleton for inhibiting DNA oxidation. Additionally, the Knoevenagel-related MCRs also become efficient strategies for achieving radical-scavengers. On the other hand, the Ugi 4CR and Passerini 3CR result in the dipeptide and α-acyloxycarboxamide, respectively, with the benefit for the integration of antioxidative features by aliphatic chains. Therefore, MCRs have emerged as efficient tools for integrating multiple antioxidative features into one molecule in order to meet with complicated requirements from various biological surroundings.