Anti-arthritic and anti-inflammatory effects of (-)-Epicatechin-3-O-β-d-allopyranoside, a constituent of Davallia formosana.

(-)-Epicatechin-3-O-β-d-allopyranoside (ECAP) is isolated from the popular Chinese herbal medicine Davallia formosana, which has been used to treat bone diseases including bone fracture, arthritis, and osteoporosis.To investigate the antiarthritic and the anti-inflammatory effect of ECAP on a mouse model of collagen-induced arthritis (CIA) and in vitro.

Male DBA/1 J mice were immunized by administering an intradermal injection of 100 µg of type II collagen in Freund's complete adjuvant. The control groups (vehicle) and ECAP were administered orally at doses of 1 ml/kg (H₂O), 50 and 100 mg/ml/kg once a day from Day 22 to Day 42 after primary immunization. Paw swelling, arthritis severity score, and histological changes were examined. Enzyme-linked immunosorbent assay was used to measure the levels of cytokines, including tumor necrosis factor alpha (TNF-α), interleukin (IL)-10, IL-17, IL-4, and interferon-γ (IFN-γ), in splenocytes. Furthermore, the anti-inflammatory activities of ECAP were investigated in vitro by measuring nitric oxide (NO) levels in lipopolysaccharide (LPS)-activated RAW264.7 macrophages.

In the CIA model, the oral administration of ECAP ameliorated paw edema and reduced the arthritis severity score and disease incidence. Histopathological examination demonstrated that ECAP treatment effectively protected the bone and cartilage of knee joints from erosion, lesion formation, and deformation compared with the vehicle treatment. ECAP also reduced IL-1β and MMP-9 expression in inflamed joints. Compared with the vehicle-treated mice with CIA, the reduced severity of the disease in ECAP-treated mice was associated with decreased levels of TNF-α and IL-17 and increased levels of IL-10 and IL-4 in the supernatants of splenocyte cultures. Flow cytometry analysis demonstrated that ECAP increased the population of CD4⁺CD25⁺ regulatory T cells, thereby inhibiting the B cell population. Anticollagen IgG1 and IgG2a levels decreased in the serum of ECAP-treated mice. ECAP suppressed LPS-induced NO production in RAW264.7 macrophages.

The administration of ECAP effectively suppressed inflammation and inflammatory pain and adjuvant-induced arthritis, indicating its therapeutic potential in the treatment of rheumatoid arthritis.