Protective effects of burdock (Arctium lappa Linne) on oxidation of low-density lipoprotein and oxidative stress in RAW 264.7 macrophages

The protective effects of burdock (Arctium lappa Linne) on oxidation of low-density lipoprotein (LDL) and nitric oxide production were investigated. The results showed that methanolic extracts of burdock (MEB) and their major components, chlorogenic acid (CHA) and caffeic acid (CA), showed marked antioxidant activity against oxidative damage of liposome (p < 0.05), deoxyribose (p < 0.05) and protein (p < 0.05). In addition, at a concentration of 500 μg/ml, the inhibitory effect of MEB on LDL oxidation was 66.9% compared to the control (p < 0.05). MEB, at 200 μg/ml, not only enhanced GSH levels, but also increased activity of GSH reductase, GSH peroxidase, GSH transferase and catalase, which were 3.82-, 24.9-, 4.35- and 3.02-fold compared to the control (p < 0.05), respectively. MEB directly scavenged nitric oxide in a concentration-dependent fashion (p < 0.05). Moreover, MEB showed a reducing effect on nitric oxide production of lipopolysaccharide (LPS)-induced RAW 264.7 cells. The expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) in activated RAW 264.7 cells were inhibited by MEB. Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed that the expression of iNOS and COX-2 mRNA in activated macrophages were suppressed by a high concentration (500 μg/ml) of MEB. Furthermore, a downregulated degradation of IκB-α by MEB was found, indicating that MEB reduced iNOS enzyme expression as a result of preventing NF-κB activation. These results suggest that MEB displays an inhibitory action on biomolecules and has a bioactive action for attenuating excessive NO generation at inflammatory site as well as in cardiovascular disease.