S. Ghahari - Department of Organic Chemistry, Faculty of Chemistry, University of Mazandran, Babolsar, Islamic Republic of Iran.
H. Alinezhad - Department of Organic Chemistry, Faculty of Chemistry, University of Mazandran, Babolsar, Islamic Republic of Iran.
Gh. A. Nematzadeh - Genetics and Agricultural Biotechnology Institute of Taberestan (GABIT), Sari Agricultural Sciences and Natural Resources University, Islamic Republic of Iran.
M. Tajbakhsh - Department of Organic Chemistry, Faculty of Chemistry, University of Mazandran, Babolsar, Islamic Republic of Iran.
R. Baharfar - Department of Organic Chemistry, Faculty of Chemistry, University of Mazandran, Babolsar, Islamic Republic of Iran.

This study examines the chemical composition of the essential oil of Xanthium strumarium fruits, and evaluates its antioxidant and antimicrobial activities on various plant pathogens that commonly cause irreparable damages to agricultural crops. The essential oil of X. strumarium fruitswas analyzed by Gas Chromatography coupled to Mass Spectrometry (GC/MS). Antimicrobial activity was tested against ۱۴ microorganisms, including three gram-positive, five gram-negative bacteria and six fungi, using disk diffusion method and the Minimum Inhibitory Concentration (MIC) technique. The X. strumarium fruitswere also subjected to screening for possible antioxidant activity by using catalase, guaiacol peroxidase, superoxide dismutase enzymes and ۲, ۲-DiPhenyl-۱-Picryl Hydrazyl (DPPH) assay. Thirty six components were identified, representing ۹۷.۸۹% of the total oil, with methyl linoleate (۴۰.۶۴%), methyl oleate (۱۳.۱۲%), and methyl palmitate (۱۲.۴۳%) being the major ingredients. The essential oil showed significant activity against Rathayibacter toxicus (MIC= ۲۵ µg mL-۱), and Pyricularia oryzae (MIC= ۱۲.۵ µg mL-۱). In addition, the analysis of free radical scavenging activities of the X. strumarium fruitsrevealed antiradical activity of ۱۳۸.۸۷ µg mL-۱ in DPPH, ۳۲.۷۶۶ µmole activity/mg protein in catalase, ۵.۵۶۷ mmol activity/mg protein in guaiacol peroxidase and ۱.۷۱۴ U mg-۱ protein in superoxide dismutase. Furthermore, the phytochemical analysis showed moderate to good amounts of alkaloid (۰.۵۴ mg g-۱), phenolic (۵۴.۴۴ mg g-۱) and flavonoid (۲۰.۱۱ mg g-۱) compounds in X. strumarium fruits. Our results suggest that this plant may be a potential source of biocide, for economical and environmentally friendly disease control strategies. It may also be a good candidate for further biological and pharmacological investigations.

Antibacterial activity, Antifungal effect, Antioxidant activity, Plant pathogens, Xanthium strumarium Linn