Abstract: 
The aim of the present study is to evaluate the in vitro anti-arthritic effect of thymoquinone (TQ), the possible protective effects of TQ against collagen II-induced rheumatoid arthritis, in male rats with influence of orally TQ treatment in rheumatoid arthritis score and its effect on the accompanying xanthine oxidase activity, in plasma, liver and spleen homogenates. In vitro anti-arthritic activity was evaluated using BSA denaturation inhibition test. Rheumatoid arthritis was induced in rats by intradermal injection of collagen II at dose of 03 mg/kg, emulsified in Complete Freund’s Adjuvant (V/V), the arthritic rats were treated with TQ for 40 days, using two doses (05 and 10 mg/kg). Then, xanthine oxidase activity was estimated in both plasma and tissue homogenates of arthritic and TQ-treated rats, using spectrophotometry methods. This study revealed a significant in vitro anti-arthritic activity in dose dependent manner. Collagen II-induced rheumatoid arthritis is accompanied by a significant increase of xanthine oxidase activity in plasma, liver and spleen. In addition, TQ treatment led to restore xanthine oxidase activity in a dose dependent manner. Thymoquinone possesses significant anti-arthritic activity which expressed by the decreased arthritic score, a delay in the onset of the disease and inhibition of xanthine oxidase inhibition activity, in both plasma and tissue homogenates.

Keywords: Rheumatoid Arthritis, Collagen, Thymoquinone, Xanthine Oxidase, Anti-Arthritic.