Immune-regulatory activity of methanolic extract of Acacia confusa heartwood and melanoxetin isolated from the extract

The antioxidant, anti-inflammatory, antivirus, uric acid decreasing, and hepatoprotective activities of Acacia confusa extracts were demonstrated in previous studies. However, there is no scientific evidence concerning the immune-regulatory activity of the heartwood extract of A. confusa. In this study, the effect of a methanolic heartwood extract (MHE) from A. confusa on dendritic cell (DC) activation and function was examined. A. confusa MHE significantly reduced the production of pro-inflammatory cytokine interleukin-6 (IL-6) in lipopolysaccharide (LPS)-stimulated DCs, and the effective concentration (25 μg ml^-1) of A. confusa MHE did not affect cell viability. Additionally, the bioactive phytochemical from A. confusa MHE, melanoxetin, was isolated and purified by HPLC. This substance inhibited the production of pro-inflammatory cytokines (tumor necrosis factor-α, IL-6, and IL-12) in LPS-stimulated DC at a concentration of 12.5 μM. Moreover, the expression levels of co-stimulatory molecules such as CD40, CD80, and CD86 also remarkably decreased after treatment with melanoxetin at the same dose. These findings indicate that A. confusa MHE and melanoxetin have excellent immune-suppressive activity and may be potential candidates for further development of natural health supplements.