Scavengers properties

Fig. 16.6 The 1,3-diphenyl propane skeleton of flavonoids and the numbering system for flavonoids. Three structural features optimise the radical scavenging properties of a flavonoid (i) an orto-dihydroxy structure of the B-ring (catechol) (ii) 2,3 double bond in conjugation with a 4-oxo group (iii) 3- and 5-hydroxy groups (Bors and Saran, 1987).

Rozanowska, M. et al., Free radical scavenging properties of melanin interaction of eu- and pheo-melanin models with reducing and oxidising radicals. Free Rad. Biol. Med., 26, 518, 1999. 

L. Campanella, G. Favero, L. Persi, and M. Tomassetti, New biosensor for superoxide radical used to evidence molecules of biomedical and pharmaceutical interest having radical scavenging properties.. /. Pharrn. Biomed. Anal. 23, 69—76 (2000). 

Visioli F, Bellomo G and Galli C. 1998. Free radical-scavenging properties of olive oil polyphenols. Biochem Biophys Res Commun 247(l) 60-64. 

The absence of substituents with free radical scavenging properties in most of the (3-blockers makes doubtful their efficacy as powerful antioxidants. Arouma et al. [293] tested the antioxidative properties of several 3-blockers in reactions with superoxide, hydroxyl radicals, hydrogen peroxide, and hypochlorous acid. It was demonstrated that most of the compounds tested were inactive in these experiments. Nonetheless, propranolol, verapamil, and flunarizine effectively inhibited iron ascorbate-stimulated microsomal lipid peroxidation and all drugs (excluding flunarizine) were effective scavengers of hydroxyl radicals. Contrary to Janero et al. [292], these authors did not find the inhibition of xanthine oxidase by propranolol. It was concluded that 3-blockers are not the effective in vivo antioxidants. 

Marcocci L, Maguire JJ, Droy-Lefaix MT, Packer L. (1994). The nitric oxide-scavenging properties of Ginkgo biloba extract EGb 761. Biochem Biophys Res Community. 201(2) 748-55. 

The high efficiency and selectivity of the natural siderophores in binding iron(lll) inspired attempts to develop siderophore analogs with improved iron-scavenging properties amenable for chelation therapy. A most pertinent example is desferrioxamine B (DFO), where low patient compliance generates the need for developing oral means of administration for... 

A water-soluble Cj-symmetrical trisadduct of Cjq showed excellent radical scavenging properties in vitro and in vivo and exhibits remarkable neuro-pro tective properties [7,8]. It is a drug candidate for the prevention of ALS and Parldnsoris disease. Concerning the reaction mechanism, nucleophilic additions and radical additions are closely related and in some cases it is difficult to decide which mechanism actually operates [92]. For example, the first step in the reaction of f-eo with amines is a single electron transfer (SET) from the amine to the fullerene. The resulting amines are finally formed via a complex sequence of radical recombinations, deprotonations and redox reactions [36]. 

Most of these compounds, e.g. quercetin, possess various degrees of antioxidant or free radical scavenging properties. A number of phenolic compounds have medicinal properties and have long been used as drugs. For example, etoposide and teniposide, two lignans, are anticancer drugs. 

Taken together, these results reveal that EGb prevents not only the ascorbic arid/Fe2 4-induced impairment in amine uptake and membrane fluidity by generating free radicals, but also the impairment in age-related membrane fluidity. This preventive effect of EGb is probably due to its radical scavenging properties. 

Miura D, Miura Y, Yagasaki K. 2004. Resveratrol inhibits hepatoma cell invasion by suppressing gene expression of hepatocyte growth factor via its reactive oxygen species-scavenging property. Clin Exp Metastasis 21 445 451. 

By using the S0D/H202 biosensor set up in our laboratory, we recently evaluated the scavenging properties in vitro of important molecules such as cysteine, melatonin, /(-carotene and acetyl salicylic acid to be considered as antitoxic agents against radicals as well as of fresh vegetal and fruit tissues, or else of extracts of the same fruits and vegetals present on the market and available in the chemists or herbalists shops. 

The production of superoxide anions is one of the major factors involved in NO toxicity because superoxide anions can react with NO to form the highly toxic free-radical peroxynitrite. A pivotal role for superoxide anions in NO-related insults is emphasized by results showing that transgenic mice overexpressing superoxide dismutase (SOD) are resistant to brain ischemia. Superoxide can protect against SNP-induced toxicity. Thus, the superoxide-scavenging properties of EGb 761 are likely to explain, at least in part, its ability to block cell death and the increase in reactive oxygen species accumulation induced by the two NO donors used here, SNP and SIN-1. 

---