Structural elucidation and in vivo anti-arthritic activity of β-amyrin and polpunonic acid isolated from the root bark of Ziziphus abyssinica HochstEx. A Rich (Rhamnaceae).

Two natural products, compounds 1 and 2 were isolated from the root bark of Ziziphus abyssinica for the first time and were structurally elucidated as β-amyrin and polpunonic acid, respectively. Both compounds were further subjected to an in vivo study in rats to evaluate their anti-arthritic potency. Compared to the arthritic control group, rats treated with different doses of 1 or 2 (3, 10, and 30 mg/kg) exhibited significantly higher total change in body weight as well as lower arthritic scores and total change in paw edema and erythema. Histopathological examinations of the hind paws of the rats further demonstrated the beneficial effects of both compounds as they significantly reversed cartilage erosion, subchondral cyst, and Weichselbaum's lacunae formation. Evidence of bone remodeling was also observed in all groups of rats treated with 1 or 2. Hematological and serum biochemical parameters were not significantly affected by treatment of 1 or 2. Taken together, the results from the present study suggest potential therapeutic benefit of β-amyrin and polpunonic acid in rheumatoid arthritis and related inflammatory disorders.