Anti-radical activity

Antioxidant/anti-radical activity and chelation of metal ions... 

Antioxidant and anti-radical activity, chelation of metal ion... 

The constant of inhibiting rate k, determining the anti-radical activity of AO and being its qualitative characteristic, is found from relation Eq. (2), using the known constant of chain continuation rate k, concentration... 

Diabetic patients have reduced antioxidant defences and suffer from an increased risk of free radical-mediated diseases such as coronary heart disease. EC has a pronounced insulin-like effect on erythrocyte membrane-bound acetylcholinesterase in type II diabetic patients (Rizvi and Zaid, 2001). Tea polyphenols were shown to possess anti-diabetic activity and to be effective both in the prevention and treatment of diabetes (Choi et al, 1998 Yang et al, 1999). The main mechanism by which tea polyphenols appear to lower serum glucose levels is via the inhibition of the activity of the starch digesting enzyme, amylase. Tea inhibits both salivary and intestinal amylase, so that starch is broken down more slowly and the rise in serum glucose is thus reduced. In addition, tea may affect the intestinal absorption of glucose. 

Lim, B. P., A. Nagao et al. (1992). Anti-oxidant activity of xanthophylls on peroxyl radical-mediated phospholipid peroxidation. Biochim. Biophys. Acta 1126 178-184. 

By contrast, other compounds in food may decrease cancer risk (Table 21.7). Free radical scavengers such as the antioxidants, vitamins E and C, carotenoids and fla-venoids have anti-cancer activity, while vitamins A and D and other retinoids may encourage a cell to differentiate rather than proliferate (Box 21.4). Plant oestrogens in soya prodncts may be protective since they compete with human oestrogens for the oestrogen receptors in breast and ovary bnt elicit no response. 

Andrographolide, thus, has different mechanisms of anti-inflammatory activity. It can inhibit the activation of NF-kB, suppress inducible nitric oxide synthase (iNOS) expression, inhibit COX-2 expression in human fibroblast cells and also prevent oxygen radical production by human. The compound is also able to modulate T-cell activation both in vitro as well as in vivo, it is evident that it could prevent initial T-cell priming by interfering with DC maturation and antigen presentation capacity. Therefore, andrographolide may have utility as a therapeutic agent for the treatment of autoimmune diseases, such as multiple sclerosis. " ... 

Anti-inflammatory activity. Extract of the green seed, administered externally to adult with skin inflammations by free radical inhibition at a concentration of 1%, was active . 

The anti-inflammatory activity of the NSAIDs is mediated chiefly through inhibition of biosynthesis of prostaglandins (Figure 36-2). Various NSAIDs have additional possible mechanisms of action, including inhibition of chemotaxis, down-regulation of interleukin-1 production, decreased production of free radicals and superoxide, and interference with calcium-mediated intracellular events. Aspirin irreversibly acetylates and blocks platelet cyclooxygenase, while most non-COX-selective NSAIDs are reversible inhibitors. 

Baeyer-Villiger oxidation has been used to selectively oxidize one of two methyl ketones (to esters) in the final step of a stereoselective synthesis of (—)-acetomycin, an antibiotic with potential anti-leukemia activity (equation 25)135. This reaction was accomplished using MCPBA as oxidant, with an excess of sodium bicarbonate and 5-/er/-bulyl-4-hydroxy-2-melhyl phenyl sulfide as a radical inhibitor. 

Clofazimine [kloe FA zi meen] is a phenazine dye that binds to DNA and inhibits template function. Its redox properties may lead to the generation of cytotoxic oxygen radicals that are also toxic to the bacteria. Clofazimine is bactericidal to M- leprae and has some activity against M- avium intracellulare complex. On oral absorption, it accumulates in tissues, allowing for intermittent therapy, but it does not enter the CNS. Patients may develop a red-brown discoloration of the skin. Eosinophilic enteritis has been reported as an untoward effect. The drug also has some anti-inflammatory activity, thus erythema nodosum leprosum does not develop. 

The pharmacology of these drugs, which are also used in the treatment of malaria, is presented on p. 351. The mechanism of their anti-inflammatory activity is uncertain. Besides inhibiting nucleic acid synthesis, they are known to stabilize lysosomal membranes and trap free radicals. In treating inflammatory disorders, they are reserved for rheumatoid arthritis that has been unresponsive to the NSAIDs or else they are used in conjunction with an NSAID, which allows a lower dose of chloroquine or hydroxychloroquine to be administered. These drugs have been shown to slow progression of erosive bone lesions and may induce remission. They do cause serious adverse effects (see p. 351). 

A, anti-oxidation activity evaluated by the neutralizing of DPPH as a model radical compound B, inhibition activity against mouse melanoma tyrosinase measured using L-DOPA as a substrate. Open circle, P-Arb closed circle, the coupling product (Arb-GA) open triangle, GA. 

The /3-diketone moiety in conjugation with the phenolic groups contributes greatly to the anti-inflammatory and anti-tumor activity of curcumin/ The rate constants for the reactions of several oxidizing free radicals with quercetin and curcumin are given in Table 2. 

Effects on antioxidant enzymes. Along with anti-radical effects camosine can influence enzymes which activity is connected directly or indirectly to free radical metabolism. Camosine and other CRC may work as NO synthase inhibitors in muscles [54]. Low concentrations of camosine (until 2.5 mM) can activate rabbit platelets 5 -lipoxygenase, whereas higher concentrations inhibit it [55]. Camosine, homocamosine or anserine (15-25 pM) inhibit rat brain tirosine hydroxylase by 50% at very low concentrations [56]. It was demonstrated recently that camosine may protect SOD from ROS attack under in vitro [57], and in vivo (our unpublished data) oxidative stress. 

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