Origanum vulgare L (oregano) is a flavoring herb widely used around the world. In the present study, crude extract of O. vulgare L (oregano) and its petroleum ether, chloroform, ethyl acetate, n-butanol, water fractions were prepared in order to isolate and investigate antimutagenic compounds from the active extract through the bacterial genotoxicity assay guided fractionation procedures. The methanol extract and its n-butanol fraction showed significant antimutagenic activity. In the end of sub-fraction-ation process of the n-butanol extract, luteolin 7-O-glucuronide and luteolin 7-O-xyloside were isolated. These compounds showed significant antimutagenic activity against 9-Aminoacridine and N-Methyl-N'nitro-N-nitrosoguanidine mutagenicity. The inhibition rates ranged from 22.1% (luteolin 7-O-xyloside: Salmonella typhimurium TA1537 - 0.4 mM/plate) to 67.8% (luteolin 7-O-glucuronide: S. typhimurium TA1537 - 0.8 MM/plate). In conclusion, the results revealed that luteolin 7-O-glucuronide and luteolin 7-O-xyloside are two of the antimutagenic compounds of O. vulgare L ssp. vulgare. (C) 2011 Elsevier Ltd. All rights reserved.