Abdulsattar J. Abdullah, Zahraa M. A. Hamodat*

Department of Chemistry, College of Science, University of Mosul, Iraq;
*e-mail: zahraahamodat@uomosul.edu.iq

Received: 20 April 2025; Revised: 01 June 2025;
Accepted: 11 June 2025; Available on-line: 07 July 2025

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation and oxidative stress. Fibrinogen-like protein-1 (FGL1) has been implicated in immune regulation, but its antioxidant role under inflammatory conditions remains underexplored. This study aimed to isolate and purify FGL1 from the serum of healthy controls and from the serum and synovial fluid from inflamed joints of RA patients, and to assess its antioxidant capacity. Purification included ammonium sulfate precipitation (65%), dialysis, and gel filtration chromatography (Sephadex G-75), SDS-PAGE and HPLC. Antioxidant activity was evaluated by DPPH radical scavenging and IC₅₀ calculation. SDS-PAGE and HPLC analysis confirmed the successful isolation, identity and high purity of FGL1 from all samples, the protein molecular weight ranged from 68 to 70 kDa. The DPPH assay showed that FGL1 isolated from synovial fluid of RA patients had the highest antioxidant activity (IC₅₀ = 2.124 ng/ml), followed by RA serum (2.172 ng/ml) and control serum (2.798 ng/ml). These results indicate the dual role of FGL1 protein in immune response and oxidative balance, making it a promising biomarker and potential therapeutic target in rheumatoid arthritis.