Isolation of antioxidative compounds from Brazilian propolis: 3,4- dihydroxy-5-prenylcinnamic acid, a novel potent antioxidant

Abstract

One new and 11 previously known antioxidative compounds were isolated from Brazilian propolis. The new compound was determined as 3,4-dihydroxy-5- prenylcinnamic acid (3-[3,4-dihydroxy-5-(3-methyl-2-butenyl)phenyll-2-(E)- propenoic acid) by various physical analyses (MS, IR, 1H-NMR, 13C-NMR, and 2D-NMR). The inhibitory activity of each compound against peroxidation of linoleic acid in a micelle solution was measured. We found that the novel compound possessed the highest potency (IC50, 0.17 μ) among them and was more effective than butylated hydroxytoluene (BHT; IC50, 0.36 μM) under the experimental conditions employed. Among the isolated antioxidative compounds, 3,5-diprenyl-4-hydroxycinnamic acid (artepillin C; IC50, 0.44μM) was found to be most abundant in Brazilian propolis.