Effect of 6＇-acetylpaeoniflorin on dinitrochlorobenzene induced allergic contact dermatitis in BALB/c mice

Aim The present study aimed to investigate anti-inflammatory activity of 6-AP on murine model of aller- gic contact dermatitis （ACD）. Methods 6＇-acetylpaeoniflorin （6-AP） was synthesized from paeoniflorin （Pae） via acetylation and the structure was characterized by 1H-NMR, 13C-NMR and EI-MS. ACD model was established by repeated application of dinitrochlorobenzene （DNCB） to induce skin immune inflammation. The mice were oral- ly administered 6-AP （35, 70, 140 mg. kg-1 ·d^-l）, Pae （70 rag. kg-1·d^-1） and prednisone （Pre, 5 rag. kg^- 1· d^-1 ） from day 1 to day 7 after Cutaneous inflammation was evaluated by ear swelling and histological exami- nation. Splenocyte proliferation was assayed by the 3-（4, 5-dimethylthiazol-2-yl）-2, 5-diphenyl-2H tetrazolium bromide assay. The cytokine production in the splenocytes was measured by enzyme-linked immunosorbent assay. Results Topical application of DNCB to the skin provoked obvious swelling and inflammatory cell infiltration. 6- AP significantly inhibited ear swelling, decreased inflammatory cell infiltration and epidermal keratinization. Ad- dtionally, 6-AP obviously alleviated the hyperplasia of red pulp and germinal center （GC） appearance, decreased spleen index, decreased spleen index, and inhibited splenocyte proliferation in ACD model, compared to that of Pae. Further, the study indicated that 6-AP treatment could increase IL-10 level, while reduce IL-17 level in splenocytes simultaneously. The correlation analysis displayed significantly positive correlations between IL-17 level and the severity of skin inflammation, while negative correlations between IL-10 level and skin inflammation. Con- clusion 6-AP has a significantly higher anti-inflammatory effect than Pae, and it may be a useful treatment for ACD.