Plants are an important resource of medical preparations. Recently, most studies have concerned medicinal plants to take benefit of their active ingredients as antioxidants. Rheum palaestinum Feinbr is one of Rheum genus grown in syria. This study aimed to investigate the antioxidant activity and the total content of phenols, flavonoids and anthraquinones of different extracts of Rheum Palaestinum roots and aerial parts. The total content of phenols was determined with Foln-Ciocalteau reagent, flavonoids content with aluminum chloride reagent and anthraquinones by UV-vis spectrophotometric method then the antioxidant activity was performed by in vitro using different antioxidant tests. The results showed that the ethanolic roots extract had the highest phenolic content (512.15mg GAE/g dry extract), the highest flavonoids content (48mg QE/g dry extract) and the highest anthraquinones content (14.74mg Rhein E/g dry extract) as well as it has the highest antioxidant activity in all tests. While the lowest phenolic content (322.85mg GAE/g dry extract), the lowest flavonoids content (21.08mg QE/g dry extract), the lowest anthraquinones content (2.04mg Rhein E/g dry extract) and the least antioxidant activity was in aqueous extract of aerial parts. Based on these results, it could be concluded that this plant is a rich source of phenolic compounds so it is interesting to be developed as an alternative herbal medicine.
