AbstractExtracts from the inner stem bark of Berberis vulgaris were analyzed for their antioxidant activity using the 1,1-dipheny-2-picrylhydrazyl (DPPH) method and compared with ascorbic acid (AA) and butylated hydroxytoluene (BHT). The most active extracts were analyzed for their chemical composition using gas chromatography-mass spectrometry. Acetone extract was found to be the most active as an antioxidant agent at 98.61%, which was higher than the value of vitamin C (93.03%) at the concentration of 0.16 mg/mL. The major components identified in the acetone extract were tetracosanoic acid, methyl ester (26.36%), followed by phthalic acid, diisooctyl ester (20.93%), 1,2-bis(trimethylsiloxy) ethane (10.26%), and 1,2-benzendicarboxylic acid, diisononyl ester (8.70%). The dissolved water:methanol (1:1 v/v) partitioned from acetone extract afforded 12 fractions; among them, fraction F11 was found to have good antioxidant activity (95.41%) at the concentration of 0.16 mg/mL. The major compounds identified in F11 were N-methyl-4-(hydroxybenzyl)-1,2,3,4-tetrahydroisoquinoloine (28.82%), 9-α-hydroxy-17β-(trimethylsilyl-oxy)-4-anderostene-3-methyloxime (13.97%), ribitol, pentaacetate (9.76%), 1-methyl-4-[4,5-dihydroxyphenyl]-hexahydropyridine (6.83%), and 2-ethylacridine (4.77%).