Silybum marianum seeds has traditional uses as reconstitute, stimulant, diuretic and expectorant. The aim of this study was to determine the important phytochemical characteristics of Silybum marianum seeds collected from different parts of Iran. Important characteristics of this plant include essential oil content, total phenol and flavonoid content and various radical scavenging activities. Based on obtained results, S. marianum grown in Naghadeh showed the highest oil content (20.0%) percentage, followed by Urmia (19.36 %), Saghez (19.17%), Khoy (18.85%), Marivan (18.56%) and Jolfa (18.34%), respectively. Total phenolic content of S. marianum was of the order: Marivan (29.58 mg GAE g-1 DW), Naghadeh (28.75 mg GAE g-1 DW), Khoy (28.64 mg GAE g-1 DW), Saghez (28.33 mg GAE g-1 DW), Jolfa (27.87 mg GAE g-1 DW), and Urmia (27.03 mg GAE g-1 DW). The highest (3.11 mg QE g-1 DW) and the lowest (2.31 mg QE g-1 DW) total flavonoid content of S. marianum seeds were observed in Marivan and Urmia, respectively. The plants grown in Naghadeh area showed the highest radical scavenging activities, including DPPH (58.31%) and nitric oxide (29.76%), whereas the highest super oxide radical scavenging activity was obtained in Saghez (92.27%). According to results, no noticeable differences were observed in total phenol and flavonoid contents in various studied sites. Whereas, oil content, DPPH, super oxide and nitric oxide radical scavenging activities varied in the different studied sites. Therefore, different climate changes significantly affect the phytochemical composition of S. marianum and as such, should be the focus of medical studies.

Key words: Essential oil, phytochemical properties, radical scavenging activity, Silybum marianum.