Synthesis and antioxidant activity of prenylated resveratrol

Resveratrol derivatives have been reported to have important bioactivities. Synthesis of monomeric resveratrol derivatives has been a challenging topic in both organic and medicinal chemistry. A Synthesis of prenylated resveratrol was developed through prenylation between resveratrol (3,5,4'-trihydroxystilbene) and prenyl bromide (3,3-dimethyl allyl bromide) using heterogeneous superbase catalyst γ-Al ₂ O ₃ /NaOH/Na. The aim of this research is to obtain prenylated resveratrol compound that has important bioactivity and to identify a type of prenylation, O-or C-prenylation. Characterization of the product was carried out using liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance ( ¹ H-NMR). The antioxidant activity of the samples was determined using DPPH radical scavenging assay. The results of LC-MS analysis of the product showed the molecular ion peak at m/z 365.38 [M+H] ⁺ that indicated the presence of prenylated resveratrol with two prenyl (C ₅ H ₉ -) substituent. The ¹ H-NMR spectrum of the product indicated that the addition of two prenyl substituent occurs at the hydroxyl group on the structure of resveratrol (O-prenylation). Prenylation caused decreasing free radical scavenging activity of the product (IC ₅₀ = 102,75 ppm) compared to resveratrol (IC ₅₀ = 63,52 ppm) and it means that the addition of prenyl substituents occurs through O-prenylation.