Context: Rheumatoid arthritis is a chronic, autoimmune and systemic inflammatory disease, which targets synovial joints leading to joint destruction mediated in part by migration of inflammatory cells into the synovial tissue. Objective: The present study evaluates the anti-rheumatic effect of a methanol extract of Ananas comosus (L.) Merr. (Bromeliaceae) peel in rats. Materials and methods: Anti-rheumatic activity of crude extract of peels of A. comosus in complete Freund's induced arthritis model in rats was studied at doses of 50, 100, 250 and 500 mg/kg b.w. for 21 days. Parameters such as paw size, levels of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), C-reactive proteins (CRP) and prostaglandins (PGE 2 ) were analysed. Results: Oral administration of the extract significantly reduced the swelling in the paw of rats (EC 50 65.1 ± 2.95 mg/kg b.w.) with a maximal inhibition of 77.01 ± 10.53% on 21st day at 500 mg/kg b.w. The extract also significantly reduced the levels of SOD, CAT and GPx in liver (EC 50 26.84 ± 16.37, 68.37 ± 19.22, 106.54 ± 34.81 mg/kg b.w., respectively), kidney (EC 50 261.75 ± 81.5, 176.38 ± 8.08, 14.32 ± 6.64, mg/kg b.w., respectively) and spleen (EC 50 152.14 ± 39.57, 83.97 ± 14.6, 47.1 ± 10.45 mg/kg b.w., respectively); and CRP (EC 50 36.37 ± 12.4 mg/kg b.w.) and PGE 2 (EC 50 191.06 ± 71.54 mg/kg b.w.) in tissue homogenate and serum, respectively, at 500 mg/kg b.w. as compared to arthritic control group. Discussion and conclusion: These results suggest that A. comosus fruit peel extract exerts anti-rheumatic activity.ARTICLE HISTORY

Ananas comosus (L.) Merr (Pineapple) is a tropical plant with an edible fruit. In the present study, the potential anti-inflammatory activity of A. comosus leaf extract (ALE) was studied. ALE prepared using soxhlet apparatus was subjected to preliminary qualitative phytochemical analysis and quantitative estimations of flavonoids and tannins. The components present in ALE were identified using liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS). Inhibitory effects of ALE on protein denaturation, and proteinase activity were assessed. Its effect on secretion of pro-inflammatory cytokines and inflammatory mediators by lipopolysaccharide-stimulated macrophages was also analyzed. Further, its anti-inflammatory activity in carrageenan-induced inflammatory rat model was examined. The preliminary qualitative phytochemical analysis revealed presence of flavonoids, phenols, tannins, carbohydrates, glycosides, and proteins in the extract. Total flavonoids and total tannins were 0.17 ± 0.006 mg equivalent of quercetin/g of ALE and 4.04 ± 0.56 mg equivalent of gallic acid/g of ALE. LC-MS analysis identified the presence of 4-hydroxy pelargonic acid, 3,4,5-trimethoxycinnamic and 4-methoxycinnamic acid, whereas GC-MS analysis identified the presence of campesterol and ethyl isoallocholate that have been previously reported for anti-inflammatory activity. ALE showed significant inhibition of protein denaturation and proteinase activity and also controlled secretion of tumour necrosis factor-α, interleukin-1β and prostaglandins, as well as the generation of reactive oxygen species by activated macrophages. ALE also significantly decreased carrageenan-induced acute paw edema. The study, therefore, identified the components present in ALE that may be responsible for its anti-inflammatory activity and thus demonstrated its potential use against acute inflammatory diseases.