Background: In humans, many diseases including cancer are associated with the accumulation of free radicals. Antioxidants can scavenge free radicals and minimize those impacts. Therefore, the antioxidants are used in cosmetic products, food supplements and medicine to modify the physiological functions. There are many cancer treatment options such as surgery, radiation therapy and chemotherapy and these methods bring lots of side efects to patients. Besides, Endoxan is a medicine commonly used to treat cancer, containing a compound called cyclophosphamide. However, using cyclophosphamide has many side effects, especially it elevates lipid peroxidation. According to the Oriental Medical, the flower, leaves and root of Hibiscus rosa-sinensis are commonly used to reduce the inflammation, furuncles, etc. The aim of the study: This study proved that Hibiscus rosa-sinensis has the antioxidant activity and the ability to recover liver functions when it was coordinated with cyclophosphamide in mice model. Materials and methods: Reducing power assay, DPPH free radical scavenging assay, and lipid peroxidation assay are utilised to identify the antioxidant activity of the Hibiscus rosa-sinensis flower decoction. Results: We have defined that the decoction of Hibiscus rosa-sinensis flower exhibits reducing power at 1% concentration which the optical density value is 1.51, the IC 50 value in DPPH free radical scavenging assay is 0.13 ± 0.01% (p < 0.05) and at 1.71% concentration of the flower decoction the lipid peroxidation in the liver of the experimental group decreased 50% compared to that of the control. In the mice model, the malonyl dialdehyde level in the liver of the mice continuously drinking at 1.71% concentration of the decoction in 1 day and 7 days was 2.3 times fewer than the control. Accordingly, the malonyl dialdehyde level in the liver of the mice drinking the decoction for 7 days was 1.93 times fewer than the 1-day trial under the same exper-Оригинальная статья Original article Nguyen Thi H, et al. Study on the antioxidant capacity of … Оригинальная статья Original article