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One triterpenic acid (ursolic acid), one phenolic acid (rosmarinic acid), and four flavonoids (luteolin, luteolin 7-O-(6"-feruloyl)-β-glucopyranoside, luteolin 5-O-β-glucopyranoside, and luteolin 7-O-β-glucuronide) were isolated from the aerial parts of Thymus sipyleus subsp. sipyleus var. sipyleus and identified by spectroscopic methods. In vitro lipid peroxidation inhibition effects of the compounds were determined using TBA test method in a bovine brain liposome system. All compounds inhibited lipid peroxidation in various degrees except for ursolic acid. The order of the lipid peroxidation activities of luteolin, its glycosides and rosmarinic acid were: Luteolin 7-O-β-glucuronide> luteolin 5-O-β-glucopyranoside> luteolin 7-O-(6"-feruloyl)β-glucopyranoside > rosmarinic acid >luteolin. However, the activity order of the compounds was completely different in DPPH radical-scavenging activity. None of the compounds shows Fe 2+ chelating activity. The results were discussed based on their chemical structures and polarities.

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are various forms of activated oxygen and nitrogen, which include free radicals such as superoxide ions (O 2 · Ϫ ), hydroxyl (OH · ) and nitric oxide radicals (NO · ), as well as non-free-radical species such as hydrogen peroxide (H 2 O 2 ) and nitrous acid (HNO 2 ). [1][2][3] In living organisms ROS and RNS can form in different ways. Normal aerobic respiration, stimulated polymorphonuclear leukocytes and macrophages, and peroxisomes appear to be the main endogenous sources of most of the oxidants produced by cells. [4][5][6] Exogenous sources of free radicals include tobacco smoke, ionising radiation, organic solvents and pesticides.7-10) Free radicals can cause lipid peroxidation in foods that leads to their deterioration. 11)Oxidation does affect not only lipids. ROS and RNS may cause DNA damage that could lead to mutation. 12,13) In addition, ROS and RNS have been implicated in more than 100 diseases, including malaria, acquired immunodeficiency syndrome, heart disease, stroke, arteriosclerosis, diabetes and cancer.6,14-16) When produced in excess, ROS can cause tissue injury, whilst, tissue injury can itself cause ROS generation.12) Nevertheless, all aerobic organisms, including human beings, have antioxidant defenses that protect against oxidative damage and numerous damage removal and repair enzymes to remove or repair damaged molecules. 8,[17][18][19] However, the natural antioxidant mechanisms can be inefficient, hence dietary intake of antioxidant compounds becomes important. 5,16,20,21) Although there are some synthetic antioxidant compounds, such as butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA), which are commonly used in processed foods, it has been reported that these compounds may have side effects. [22][23][24][25][26][27][28] In addition, it has been suggested that there is an inverse relationship between dietary intake of antioxidant-rich foods and the incidence of a number of human diseases. 29,30) Therefore, research into the determination of natural antioxidant sources is important.In this study, it is aimed to determine the antioxidant activity (AA) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (DPPH-RSA), reducing powers (RP) and amount of total phenolic compounds (APC) of the some medicinal plants which have been used especially in Eastern Turkey. (AEF 21172). Activity studies were performed on decoctions (5%) and/or methanolic extracts (5%) of used parts of plants in the treatment. Extraction solvents and parts of plants were chosen by taking consideration the usage form of plants by public. Methanol extract was evaporated and then lyophilized, water extract was directly lyophilized. In the AA and DPPH-RSA studies, different concentration ranges were studied and data of 50, 100, 250 and 500 mg/l concentrations were given in all figures. MATERIALS AND METHODS Collection of Plants, Identification and ExtractionDetermination of Antioxidant Properties The in vitro antioxidant activit...

In this study, antioxidant properties of Thymus sipyleus Boiss. subsp. sipyleus var. sipyleus, Teucrium chamaedrys L., Mentha longifolia (L.) Hudson subsp. longifolia, Salvia limbata C.A. Meyer, and Thymus fallax Fisch. & Mey. were investigated. Antioxidant and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities, reducing powers, and the amount of total phenolic compounds of the extracts were studied. The highest antioxidant activity was shown by T. chamaedrys (decoction, IC 50 : 9.2 mg=ml), and the lowest one was S. limbata (decoction, IC 50 : 619.5 mg=ml). The highest DPPH radical scavenging activity was shown by T. fallax [decoction, IC 50 S: 56 mg=ml (IC 50 S is the extract concentration (mg=ml) required for 50% inhibition of the DPPH solution absorbance at 517 nm)] while the lowest one was S. limbata (decoction, IC 50 S: 335.8 mg=ml). The highest reducing power and amount of total phenolic compounds was shown by T. chamaedrys (decoction, 29.9 mg=ml ascorbic acid equivalent, 27.9 mg=ml gallic acid equivalent, respectively), and the lowest one was S. limbata (decoction, 5.1 mg=ml ascorbic acid equivalent, 9.9 mg=ml gallic acid equivalent, respectively) at 250 mg=ml extract concentration.

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