Anti-inflammatory effects of leaf extracts and identification of their metabolites.

Background/objectives: leaves have been used in traditional medicine to treat bleeding, gastritis, hemorrhoids, and halitosis. However, their mechanisms have not been elucidated.

Materials/methods: The present study prepared two leaf extracts (NLEs) using water or 50% ethanol. Inflammatory response was induced with LPS treatment, and expression of pro-inflammatory mediators (inducible nitric oxide synthase, cyclooxygenase-2, tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6 and nitric oxide (NO) and prostaglandin E (PGE) productions were assessed. To determine the anti-inflammatory mechanism of NLEs, we measured nuclear factor-κB (NF-κB) activity. Major metabolites of NLEs were also analyzed and quantified.

Results: NLEs effectively reduced the expression and productions of pro-inflammatory mediators such as IL-1β, IL-6, TNF-α, PGE, and NO. NLEs also reduced NF-κB activity by inhibiting inhibitor of NF-κB phosphorylation. Both extracts contained catechin and quercetin, bioactive compounds of NLEs.

Conclusions: In this study, we showed that NLEs could be used to inhibit NF-κB-mediated inflammatory responses. In addition, our data support the idea that NLEs can ameliorate disease conditions involving chronic inflammation.