Abstract : Hyoscyamus albus belongs to the endemic flora of Algeria. The abundance of bioactive substances in it contributes to its biological properties. Using two different polarity solvents, the goal of this study was to find out how polarity and extraction solvents affect the amount and quality of phytochemical compounds and their antioxidant activity. We conducted the quantitative and qualitative study using liquid chromatography-mass spectrometry (LC-MS). Five tests evaluated the free radical scavenging activity of all extracts: DPPH, phosphomolibdate, β-carotene, reducing power, and H2O2. The LC-MS test was able to find 15 phenolic compounds in the ethanol 80% extract. The main compound, quinic acid, had a concentration of 21.56±0.01 ppm. Ethanol 80% extract is also characterized by the best yield and abundance of alkaloids, polyphenols, hydrolysable tannins, and flavonoids, whereas acetone extracts with the three polarities 70, 80, and 96% are characterized by a high content of condensed tannins, low amounts of phenolic acids, and high antioxidant activity evaluated by the β-carotene method. The ethanol 96% extract has a lot of flavonoids and is very good at fighting free radicals, as shown by the phosphomolibdate and DPPH tests. According to the H2O2 and power reduction tests, the ethanol 70% extract has the highest rate of alkaloids and excellent antioxidant activity. To sum up, ethanol 70% is needed to get the alkaloids out of Hyoscyamus albus, ethanol 96% is needed for the flavonols, and acetone 80% is needed for the condensed tannins.