Piperine amino acid derivatives containing phenolic hydroxyl groups were synthesized using piperine as the raw material by amide hydrolysis, amidation, ester hydrolysis, and deacetalization. The obtained products were characterized by mass spectrometry and nuclear magnetic resonance. The antioxidant activity of the piperine derivatives was evaluated by the DPPH and ABTS scavenging rates and the total antioxidant capacity. The results showed that the piperine amino acid (4a–4d) had relatively weak radical-scavenging ability, while the piperine amino acid derivatives (5a–5d) containing phenolic hydroxyl groups had significant radical-scavenging effects. In addition, the total reducing ability of 5a–5d was better than that of piperine. The study also found that piperine derivatives containing phenolic hydroxyl groups played an important role in inhibiting oxidative damage in DNA and erythrocytes.
Piperine was used in this study in its raw form, and different steps, such as amide hydrolysis and amidation, were used to synthesize piperine derivatives containing a phenolic hydroxyl group. DPPH and ABTS free radical scavenging assays were used to assess piperine derivative antioxidant activities. We constructed an AAPH oxidative stress erythrocyte model to study the effect of piperine derivatives on the hemolysis rate of oxidatively damaged erythrocytes as well as the hemoglobin oxidation rate. This AAPH model was also used to determine piperine derivative effects on antioxidant enzyme activity and malondialdehyde (MDA) content. Results showed that spectroscopic methods could synthesize and identify piperine derivatives containing phenolic hydroxyl groups (H-1∼H-3). Moreover, DPPH and ABTS assay results showed that piperine derivative free radical clearance rates were higher compared with the parent compound. Additionally, piperine derivatives (H-1∼H-3) were found to provide protection to AAPH oxidatively damaged erythrocytes in their ability to inhibit AAPH-induced erythrocyte lysis, while hemoglobin oxidation was higher compared with the parent compound. Piperine derivatives may protect intracellular glutathione peroxidase (GSH-Px) antioxidant enzyme system activities, safeguarding against oxidative damage. This study synthesized novel piperine derivatives for use as potential antioxidant agent candidates.
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