The ability of Lawsonia inermis (Henna) to prevent the initiation of free radicals that cause cellular damage was investigated in vitro. The plant leaves were extracted using methanol (ME) and diethylether (EE) and the active ingredient, Lawsone (2-hydroxy 1,4-naphthaquinone) was separated by column chromatography. In the reducing power assay, the more antioxidant compounds convert the oxidation form of iron (Fe⁺³) in ferric to ferrous chloride (Fe⁺²). The reducing power capacity of the methanol and etheric extracts were significantly less than that of vitamin C. Total phenolic (TPC) and total flavonoid contents (TFC) were evaluated. In this study, etheric extract has the highest TPC and TFC. Radical scavenging activities of lawsone and the extracts were tested against DPPH, NO^•, SOD and HO^•.  The strongest free radical inhibition was demonstrated by etheric extract against radical scavengers, DPPH and SOD in a dose-dependent on IC₅₀ value of 18.17 and 137 µg/mL, respectively. Also, the activity of lawsone to scavenge nitric oxide radical was higher than that of the standard (quercetin) and (ME, EE) extracts. These results clearly indicate the useful effect of lawsone and these extracts as antioxidants and anticancer agents.