Abstract: The objective of this study is to show the effect of free radicals induced by fixed dose rate of X-rays radiation on the chemical constituents of some medicinal plants; barks of Cinnamomum verum (cinnamon), leaves of Salvia officinalis (sage) and Camellia sinensis (green tea). Four extracts (1%) were prepared for each medicinal plant; hydro-distilled, aqueous, ethanol and methanol. Each extract was subjected to X-rays radiation at rate of 1.9 Gy min-1. The UV-Visible spectra, physiochemical properties and biochemical constituents of each non irradiated and irradiated extracts were determined. The results showed that the effect of irradiation on the hydro-distilled and aqueous extract differed from alcohol extract. Favorable effect of irradiation was observed on the green tea extract. Considerable loses of total polyphenols and flavonoids quantities were observed in aqueous extracts. X-rays radiation remarkably induced degradation of allantoin and a slight changes in release nitrogen species. In conclusion X-ray radiation of medicinal plants in solutions produced dual effect in terms of improving and degrading the active ingredients depending on the extracted solution as well as the native constituents of each medicinal plant.