Search

The antioxidant/photoprotective potential of a standardized Krameria triandra (KT) root extract (15% neolignans) has been evaluated in different cell models, rat erythrocytes and human keratinocytes cell lines, exposed to chemical (cumene hydroperoxide, CuOOH) and physical (UVB radiation) free radical inducers. The extract was significantly more active (IC50 0.28 +/- 0.04 microg/ml) than the typical chain-breaking antioxidant alpha-tocopherol (IC50 = 6.37 +/- 0.41 microg/ml) in inhibiting the CuOOH-induced hemolysis in rat blood cells. The KT constituent 2-(2,4-dihydroxyphenyl)-5-(E)-propenylbenzofuran, was the most active (IC50 = 0.03 +/- 0.005 microg/ml), followed by eupomatenoid 6 (IC50 = 0.29 +/- 0.06 microg/ml) and conocarpan (IC50 = 0.77 +/- 0.08 microg/ml). The same order of potency was observed in red blood cells exposed to UVB irradiation in continuo, with IC50 values 0.78 +/- 0.08 microg/ml for KT extract, 0.18 +/- 0.02 microg/ml for 2-(2,4-dihydroxyphenyl)-5-(E)-propenylbenzofuran, 0.95 +/- 0.11 microg/ml for eupomatenoid 6, and 3.8 +/- 0.39 microg/ml for conocarpan. In cultured human keratinocytes exposed to UVB radiation (50 mJ/cm2), KT extract (2.5-20 microg/ml) significantly and dose-dependently restrained the loss in cell viability and the intracellular oxidative damage: glutathione (GSH) depletion and the rise in dichlorofluorescein (DCF), marker of peroxide accumulation, were suppressed by 20 microg/ml KT and in parallel cell morphology maintained. The cytoprotective effect of the extract was confirmed in a more severe model of cell damage: exposure of keratinocytes to higher UVB doses (300 mJ/cm2), which induce a 50% cell death. In keratinocyte cultures supplemented with 10 microg/ml, cell viability was almost completely preserved and more efficiently than with (-)-epigallocatechin 3-gallate and green tea. The results of this study indicate the potential use of Rhatany extracts, standardized in neolignans, as topical antioxidants/radical scavengers against skin photodamage.

The inhibitory properties of procyanidins (a standardized oligomeric catechin fraction) from Vitis vinifera L. seeds on the respiratory burst and on the release of granule components myeloperoxidase, beta-glucuronidase and elastase were studied in activated human neutrophils. Procyanidins strongly inhibit superoxide generation with an IC(50) of 7.2 microM, through a direct scavenging of superoxide and prevent the release from calcium ionophore activated neutrophils of beta-glucuronidase (IC(50) = 13.9 microM), myeloperoxidase (IC(50) = 7.2 microM) and elastase (IC(50) = 5.4 microM). In addition they dose-dependently inhibit the activity of myeloperoxidase released from calcium ionophore-stimulated cells with an IC(50) value of 2 microM. The monomeric constitutive unit (+)-catechin was far less active than procyanidins in all the models tested. These results evidence that procyanidins efficiently restrain the inflammatory response of activated neutrophils in vitro and whenever absorbed in vivo can prevent their oxidative discharge at the site(s) of their adhesion.

The aim of this work was to compare in the rat the cardioprotective efficacy and the total plasma antioxidant activity of a standardised Ginkgo biloba L. extract (GB) as such (300 mg/kg/day) or complexed with phosphatidylcholine (GB-PC; 1:2 w/w), after a 5 days oral administration. At the end of the treatment, the total plasma antioxidant defence was determined by the TRAP and FRAP assays, and the hearts from all groups of animals subjected to moderate ischemia (flow reduction to 1 ml/min for 20 min) and reperfusion (15 ml/min for 30 min). The recovery of left ventricular developed pressure (LVDP) at the end of reperfusion was 35-40% of the preischemic values in both control and vehicle rats, 50.2% in the GB group and 72.5% in the GB-PC pre-treated animals. Creatine kinase (CK) outflow in the perfusate from the hearts of GB and GB-PC treated animals were restrained to a different extent vs. controls (by 71% GB-PC; by 22% GB); the rate of prostacyclin (6-keto-PGF1 alpha) release was far greater in GB-PC than in GB hearts. In parallel, the GB extract significantly increased the total antioxidant plasma capacity (by 24.5% TRAP; 27.9% FRAP) only when complexed with phospholipids. This indicates an increased bioavailability of phenolic antioxidants when suitably embedded within a lipophilic carrier. The results of this study demonstrate that complexation of Ginkgo biloba with phospholipids induces in the rat, even after a short treatment a greater resistance of the heart to ischemia/reperfusion damage in respect to the native extract, due to an increased plasma antioxidant activity.

The aim of this work was to investigate in the rat the protective effect of an oral administration (one week) of Panax ginseng (PG) extract (10 mg/ml in drinking water; 1.6 g/kg/day) on myocardial post-ischemic damage induced by hyperbaric oxygen (HBO) and on the loss in functionality of the endothelium in aorta ring preparations. The hearts from control rats (no-HBO and no-HBO-PG), and from rats exposed to HBO and to HBO after PG treatment were isolated and subjected to mild ischemia and then reperfused. HBO greatly worsens the post-ischemic damage in controls, as demonstrated by the rise of left ventricular end diastolic pressure (LVEDP) and coronary perfusion pressure (CPP). PG significantly restrained the increase of LVEDP and CPP in respect to HBO-untreated rats, as well as that of CPP induced by injection of angiotensin II during pre-ischemia. In HBO control rats the reduction of the vasorelaxant effect of acetylcholine on norepinephrine precontracted aortic rings, was markedly recovered by PG; a similar trend was observed in aortic rings challenged with the nitric oxide synthase inhibitor NG-monomethyl-L-arginine (56% recovery). These results strongly indicate that PG prevents the myocardial ischemia/reperfusion damage and the impairment of endothelial functionality induced by reactive oxygen species arising from HBO exposure, through an antioxidant intervention. The in vitro radical scavenging activity of PG seems to be too weak (0.05-0.5 mg/ml) to explain by itself the cardiac and extra-cardiac protective effects, and this suggests a role also for an indirect antioxidant action of the drug (endothelial nitric oxide synthase stimulation).

The sparing/recycling effect of a highly purified, high molecular weight fraction of catechin oligomers (procyanidins) from Vitis vinifera seeds on alpha-tocopherol was studied in both homogeneous solution and in heterogeneous phase (phosphatidylcholine liposomes and red blood cells). By HPLC and electron spin resonance (ESR) spectroscopy we evidenced that tocopheroxyl radical, induced by reaction of alpha-tocopherol with the stable radical DPPH (2,2-diphenyl-1-picrylhydrazyl) is recycled by procyanidins. In addition procyanidins significantly and dose-dependently spare vitamin E from consumption (HPLC monitoring) during the autooxidation phase of the HO-induced peroxidation of phosphatidylcholine, by 23% at the lowest concentration (0.5 microM) and by 65.5% at 3 microM. In this membrane model the combination of 0.5 microM procyanidins and 2 microM alpha-tocopherol results in a marked delay in the appearance of conjugated dienes in respect to the single antioxidants (synergistic interaction), while catechin showed to be active only at 5 microM. In red blood cells oxidatively stressed by UVB exposure, procyanidins at 0.1-1.0 microM prevent vitamin E loss, markedly decrease membrane lipid peroxidation, linearly related to the concentration of vitamin E in the membranes, and significantly delay the onset of hemolysis (catechin protects between 5 and 10 microM).

An isolated rabbit heart Langendorff preparation paced electrically was used to evaluate the effects of a highly purified, high molecular weight fraction of oligomeric procyanidines isolated from Vitis vinifera seeds on myocardial reperfusion injury after 40 minutes of low flow (1 ml/min) ischemia. Infusion of the heart with 100 or 200 micrograms/ml procyanidines dose-dependently reduced ventricular contracture during ischemia (LVEDP values decreased by 28% and 51%), decreased coronary perfusion pressure (CPP), improved cardiac mechanical performance upon reperfusion, increased the release of 6-keto-PGF1 alpha into the perfusate in both the pre-ischemic and the reperfusion periods (by 68% at 200 micrograms/ml), and suppressed rhythm irregularity. This antiarrhythmogenic action was confirmed in a more severe model of ischemia (flow rate 0.2 ml/ min). The cardioprotective agent allopurinol infused at 20 micrograms/ml had effects on the contractility and on the release of 6-keto-PGF1 alpha comparable to those of 200 micrograms/ml procyanidines. The results of the second part of this study show that procyanidines are potent scavengers of several reactive oxygen species involved in the ischemia/reperfusion damage: the superoxide anion (IC50 = 5.64 microM: rate constant K = 7.55 x 10(5) M-1 s-1, determined by the phenazine methosulfate/NADH method); the hydroxyl radical (IC50 = 28 microM; rate constant K = 1.2 x 10(12) M-1 s-1, determined by the electron spin resonance spectroscopy); peroxyl radicals (IC50 = 0.025 microM and 0.35 microM, determined using two different lipid substrates, phosphatidylcholine liposomes and methyl linoleate micelles by UV spectroscopy at 233 nm). Finally, procyanidines interact with Fe2+ and Cu2+ ions (the catalysts of HO. radicals production) giving rise to strong complexes, with stability constants (log K) ranging from 9.35 to approximately 9.

The protective effect of caffeoyl derivatives (echinacoside, chlorogenic acid, chicoric acid, cynarine, and caffeic acid, typical constituents of Echinacea species) on the free radical-induced degradation of Type III collagen has been investigated. The macromolecule was exposed to a flux of oxygen radicals (superoxide anion and hydroxyl radical) generated by the xanthine/xanthine oxidase/Fe2+/EDTA system and its degradation assessed qualitatively by SDS-PAGE and quantitatively as the amount of soluble peptides (according to the 4-hydroxyproline method) released from native collagen after oxidative stress. The SDS-PAGE pattern of native collagen is markedly modified by free radical attack, with formation of a great number of peptide fragments with molecular masses below 97 kDa: in the presence of microM concentrations of echinacoside, there is a complete recovery of the native profile. Collagen degradation was, in fact, dose-dependently inhibited by all the compounds, with the following order of potency: echinacoside approximately chicoric acid > cynarine approximately caffeic acid > chlorogenic acid, with IC50 ranging from 15 to 90 microM. These results indicate that this representative class of polyphenols of Echinacea species protects collagen from free radical damage through a scavenging effect on reactive oxygen species and/or C-, N-, S-centered secondary radicals, and provide an indication for the topical use of extracts from Echinacea species for the prevention/treatment of photodamage of the skin by UVA/UVB radiation, in which oxidative stress plays a crucial role.