Sida tuberculata reduces oxidative stress and pain caused by the knee osteoarthritis.

ETHNOPHARMACOLOGICAL RELEVANCE: Knee osteoarthritis (OA) cause pain and edema, as well as unbalance between the production of reactive oxygen species and antioxidant activity. These problems interfere with the articular function, leading to a significant loss of life quality. Sida tuberculata R.E.Fr. is an herbaceous plant belonging to the Malvaceae family found in southern Brazil. This plant has traditionally been consumed as an aqueous extract and popularly used in the treatment of many diseases, with antioxidant and antimicrobial activity, reducing pain and inflammation. AIM OF THE STUDY: To verify the effects of S. tuberculata extract obtained from leaves on oxidative, toxic and nociceptive parameters induced by knee OA in rats. MATERIALS AND METHODS: Aqueous extracts of S. tuberculata were evaluated under phytochemical analyses. Knee Osteoarthritis was induced in rats with monosodium iodoacetate (1.5 mg/50 µl) and treated with S. tuberculata extract. The animals were treated orally with 3 doses of S. tuberculata extract (STE): 1.5, 5 and 15 mg/ml, for 14 days. For biochemical analyses, the following tests were performed: lipid peroxidation, carbonylated protein content, superoxide dismutase activity, non-protein thiol levels and myeloperoxidase activity. For the evaluation of pain and edema we verify mechanical and thermal hyperalgesia, spontaneous pain observation and measurement of knee edema with a caliper. For histological evaluations, the animal knee joints were removed. For toxicity evaluation, the levels of aspartate aminotransferase, alanine aminotransferase and urea, as well as the relative weight of the organs were analyzed. RESULTS: The S. tuberculata phytochemical analyses showed the majority peak corresponding to 20-hydroxyecdysone (20HE). The plant extract decreased damages related to oxidative stress in the blood serum (lipid peroxidation and carbonyl content) Overall, the STE 5 mg Group presented the greater statistical significance, in the blood serum samples, in relation to the other groups, being the most relevant result. The S. tuberculata groups presented pain decrease, lower neutrophil activity in the knee, and increased blood serum activity. The animals of S. tuberculata groups showed a decrease in mechanical hyperalgesia. The animals treated also presented lower scores for spontaneous pain. It was observed that the dose of 5 mg presented, once again, more expressive results, since the animals of this group had a higher frequency (greater number of days) with significant decrease of pain. In the histological analysis, in the STE 5 mg group, the articular cartilage lesions were observed at an intermediate point between the damage found in the MIA and Diclofenac groups. Besides that, the STE did not show significant changes in oxidative stress damage in liver and kidney samples. Blood serum samples did not indicate significant differences in liver and renal function. As well as, there were no differences in mean relative body weights in relation to control groups (Salina and MIA). CONCLUSION: S. tuberculata reduced the damage due to oxidative stress and pain caused by knee osteoarthritis in rats. In addition, the extract presented no toxicity. Our results suggest that S. tuberculata seems to have a therapeutic potential in the osteoarthritis treatment.