The antioxidant properties of new dimer and two monomers of phenolic acid amides isolated from Limoniastrum guyonianum

Limoniastramide, a new dimer of phenolic acid amide, isolated from Limoniastrum guyonianum, along with two natural monomers N-E-caffeoyl tyramine (1) and N-E-feruloyl tyramine (2), using centrifugal partition chromatography (CPC). Their structures were determined on the basis of spectroscopic data analysis. We investigate the antioxidant activities of Limoniastrum amides using various in vitro assays. Results showed that N-E-feruloyl tyramine and N-E-caffeoyl tyramine exhibited the highest DPPH scavenging activity compared to the dimer (IC50 = 0.5, 0.6 and 6.5 μg/ml, respectively). In addition, they have significant capacities to inhibit the bleaching of β-carotene. Limoniastramide presented the best activity with an IC50 value equal to 8 μg/ml. Finally, the N-E-caffeoyl tyramine showed the highest reducing power (EC50 = 26 μg/ml) compared to the other molecules. The present study found that L. guyonianum amides have effective in vitro antioxidant and radical scavenging activity which can be used in pharmacological and food industry due to their antioxidant properties.