In this study, the anti-inflammatory and oxidative stress inhibitory effects of Dendropanax morbifera, a native plant species in Korea, were studied. Methanol extracts of Dendropanax morbifera were fractionated according to polarity, and five fractions were named DPLS 1, DPLS 2, DPLS 3, DPLS 4 and DPLS 5 according to the solvent polarity.
Five antioxidant experiments were performed on five fractions of Dendropanax morbifera and the most effective antioxidant fraction of DPLS5 was obtained. As a result, the higher polar fractions of TPC had higher polyphenol contents and the TFC showed that DPLS 1 and DPLS 2 were particularly high in flavonoids.
The inhibitory effects of five fractions on the inflammation and oxidative stress were investigated using the LPS-stimulated RAW264.7 macrophages. The strong inhibitory activity against nitric oxide (NO) of DPLS 3 was observed. Therefore, pro-inflammatory cytokine secretion of DPLS 3 was analyzed and confirmed that the expression of iNOS and COX-2 was effectively reduced in the LPS-stimulated RAW264.7. In addition, DPLS 3 showed the highest inhibitory activity against intracellular ROS among the five fractions, and recovery of intracellular damage to oxidative stress was confirmed by examining mitochondrial membrane potential and antioxidant enzyme activity.
To determine the mechanism of DPLS 3, the activity of inhibiting transcription factor NF-κB and MAPKs signaling pathways were further analyzed. The results confirmed that DPLS 3 inhibited the phosphorylation of IKK and IkB which suggest the repression of the NF-κB translocation from the cytoplasm to the nucleus. In addition, the inhibition of phosphorylation of p38, JNK and ERK 1/2 were confirmed, and it was expected that the transcription of AP-1 could be suppressed.
In conclusion, DPLS 3, which has enhanced anti-inflammation effects and inhibition effects of oxidative stress, could be developed as a natural drug to treat diseases caused by inflammation such as rheumatoid arthritis.
