عصاره گل قاصدک (Taraxacum officinale) هر دو گونه اکسیژن فعال و اکسید نیتریک را سرکوب کرده و از اکسیدان برون تنی لیپید جلوگیری می کند Dandelion (Taraxacum officinale) flower extract suppresses both reactive oxygen species and nitric oxide and prevents lipid oxidation in vitro

Introduction Natural antioxidants not only protect food lipids from oxidation, but may also provide health benefits associated with preventing damage due to biological degeneration (Davies, 1995). Moreover, aerobic mammals use oxygen to maintain normal physiological functions, and up to 2% of oxygen consumption may end in the form of reactive oxygen species (ROS) (Davies, 1995; Yuan and Kitts, 1996). ROS are oxygen derivatives with unpaired orbital electrons and as a result are unstable and highly reactive. ROS include hydroxyl radical, superoxide radical, peroxyl radical and singlet oxygen (Halliwell, 1995). Though some ROS are part of normal metabolism (Davies, 1995; Halliwell, 1995), cigarette smoking and exposure to environmental oxidative stress (Halliwell and Auroma, 1997) can result in the production of exogenous sources of ROS, which may contribute to several forms of human cancer (Morse and Stoner, 1993). Exogenous antioxidants act to supplement endogenous primary antioxidants, such as a-tocopherol, in combating against  cell injury induced by oxygen radicals. In addition to ROS, reactive nitrogen species (RNS), such as nitric oxide and peroxynitrite, also have high reactivity with potentially important biological significance (Halliwell, 1995). Natural plant extracts, particularly those with abundant polyphenolic content, have been examined for their antioxidant potential in both food and biological models (Cuvelier et al., 1994; Teissedre et al., 1996; Marcocci et al., 1994; Hu and Kitts, 2000; Liao and Yin, 2000). The structure-activity relationships of polyphenolic antioxidants have been addressed in various model systems, and factors determining antioxidant activity include the amount and position of hydroxyl substitution (RiceEvans, 1995). Dandelions (Taraxacum officinale) have been used as a phytomedicine for their choleretic, diuretic, antirheumatic and anti-inflammatory properties (Bisset, 1994). The distribution of flavonoids and phenolic fractions in dandelion (Taraxacum officinale) has been documented (Williams et al., 1996), but antioxidant and free-radicalscavenging activities of dandelion flower have not been examined until recently. We demonstrated that a fractionated dandelion flower product inhibited both DNA scission and LDL oxidation induced by peroxyl radicals; however, the pro-oxidant character was shown, due to the reduction of transition metal ion, to initiate the Fenton reaction (Hu and Kitts, 2003). The purpose of this study was to examine antioxidant activity of a crude dandelion flower standardized extract against other common oxygen radicals, i.e., superoxide radical and hydroxyl radical. In addition, the effect of the dandelion flower extract (DFE) in scavenging nitric oxide and suppressing peroxyl radical-induced intracellular oxidation was also evaluated, using a mouse macrophage cell line. Materials and methods Nitro blue tetrazolium (NBT), xanthine, xanthine oxidase (EC1.1.3.22), deoxyribose, linoleic acid, 2-thiobarbituric acid, deoxyribose, bacterial lipopolysaccharide (LPS, Escherichia coli, serotype 0111:B4), superoxide dismutase (SOD, EC1.15.1.1), 2,2-diphenyl1-picrylhydrazyl (DPPH), 20 , 70 -dichlorofluorescin diacetate (DCFH-DA), Dulbecco’s modified Eagle medium (DMEM), Folin-Cioalteu reagent (2N) and gallic acid were purchased from Sigma Chemical Co. (St. Louis, MO). 2,20 -azobis (2-amidinopropane) dihydrochloride (AAPH) was purchased from Wako Chemicals USA Inc. (Richmond, VA). HPLC grade luteolin and luteolin-7-O-glucoside were obtained from Indofine Chemical Co. (Somerville, NJ). Other reagents were analytical or higher grade.