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Phenolic compounds, especially those with plant origin, constitute an essential part of the human diet due to their antioxidant properties. Antioxidants protect biological systems (nucleic acids, proteins, lipids, lipoproteins) against free radicals and reactive oxygen species. Some medicinal plants contain so high amounts of antioxidants that their use can be considerably effective for human health. The aim of this study was to evaluate the effect of flooding extraction method on phenolic compounds, flavonoids and the level of free radical scavenging properties of medicinal plants including Thyme, Hamadani Yarrow, Shirazi mountain thyme, Yarrow, Chamomile, Saffron corm hyssop Sagebrush, wormwood, Artemisia and Ziziphora clinopodioiedes, in four extraction solvents including water, methanol, acetone and ethanol. The results showed that methanol and water solvents had the highest and the lowest total phenolic, flavonoid and antioxidant activity, respectively. The results also showed that methanol extraction of Shirazi thyme and water extraction of Wormwood plant had the highest and the lowest phenol and flavonoids contents, respectively. The results of trapping the free radicals of DPPH indicated that the methanol extract of Shirazi thyme and aqueous extract of wormwood had the highest and the lowest inhibition activities, respectively. Therefore, the selection of solvent type can affect the rate of the extraction of phenolic compounds, flavonoids and antioxidant activity.