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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.
 

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Basil is an important medicinal plant, belonging to the Lamiaceae family. Basil is used for the treatment of different diseases such as stomachache, headache, constipation, fever and infections, as well as to reduce and regulate the blood sugar. Moreover, Basil is known for its antibacterial, antifungal and antioxidant properties. In this study, the impact of drought stress on phenols and flavonoids concentrations, as well as the antioxidant activities of leaf extract of three basil cultivars were investigated. Seeds of basil cultivars (mikhak, green, purple) were cultivated in sand-loamy soil and drought stresses (75%, 50% and 25% of the field capacity) were applied on six-leave plants. Experiments were conducted in a completely randomized design and three repeats. Total phenols, total flavonoids and flavonols concentrations of basil leaf extracts and their antioxidant activities were measured. The maximum values (with significant differences) of three groups of non-enzymatic antioxidants and the highest levels of antioxidant activities were observed for green cultivars under mild stresses (75% of the field capacity). It was observed that antioxidant activities were elevated by the increase of the concentration of the plant extract. Drought stress results in oxidative stress in basil plants. Phenols, flavonoids and flavonols are well-known as strong antioxidants have a role in the plant’s protection against the oxidative stress. In thrice cultivars of basil which were investigated, concentrations and abilities of these compounds to inhibit free radicals were decreased by the increase of the levels of drought stresses. It seems that both basil genotypes and drought stress levels affected the production of antioxidants studied and, consequently, have impacts on the plant inhibitory abilities against the oxidative stress.