Antiarthritic and Antioxidant Activities of Antrocaryon micraster Seed Extract and Its Fractions

Abstract

Rheumatoid arthritis (RA) is an incurable debilitating disease which attacks the joints and impairs quality of life. Antrocaryon micraster is used to treat RA in African traditional medicine. However, its antiarthritic activity has not been pharmacologically studied. This study, therefore, reports the antiarthritic and antioxidant activities of A. micraster seed extract and its fractions. The seed extract (ASE) was produced by Soxhlet extraction and partitioned into petroleum ether (ASEP), ethyl acetate (ASEE), and aqueous (ASEA) fractions. The total polyphenolic content, DPPH antioxidant activity, and in vitro arthritic activity using the protein denaturation assay were evaluated for ASE and its fractions. The arthritic activity of the crude extract (ASE) and its most effective fraction (ASEA), in the in vitro assay, were then evaluated against CFA-induced arthritis in rats. The polyphenolic constituent of ASE was estimated to be $13.00\pm 0.00$ mg/100 mg of GAE. ASEA contained the highest quantity of polyphenolic constituents ($10.76\pm 0.00$ mg/100 mg of GAE) among the fractions of the extract. ASE and ASEA produced profound antioxidant activity ($\text{I}{\text{C}}_{50}=20.17\pm 1.291$ and $19.35\pm 0.865$, respectively) which were similar to that of ascorbic acid ($\text{I}{\text{C}}_{50}=17.35\pm 0.500$) in the DPPH free radical scavenging assay. Furthermore, in vitro antiarthritic activity of ASEA was 13.63 and 5.75 times higher than the antiarthritic activity of the crude extract and diclofenac sodium, respectively. In the CFA-induced arthritis assay, both ASE and ASEA significantly ($P<0.001$) inhibited cachexia, paw edema, infiltration of inflammatory cells, pannus formation, and synovium damage. These results indicate that A. micraster seed extract and its fractions possessed significant antiarthritic activity via inhibition of oxidative stress, inflammation, protein denaturation, infiltration of inflammatory cells, and synovium injury due to its constituents such as polyphenols and phytosterols.