George Paganga's research while affiliated with King's College London and other places
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Publications (32)
Recent studies are emphasising the importance and putative modes of action of specific flavonoids as bioactive components of the diet in in vivo and in vitro models. Thus, it is important to have a clear idea of the major phenolic families of which fruit and vegetables are comprised and the levels contained therein. Regularly consumed fruit and veg...
Low-density lipoprotein (LDL) concentration in plasma is an important predictor for atherosclerosis, and desialylated LDL has been proposed to be particularly atherogenic. Atherosclerosis is also associated with vascular endothelial dysfunction. We therefore wished to test the hypothesis that removal of sialic acid residues from LDL increases its a...
After minimal sample preparation, two different HPLC methodologies, one based on a single gradient reversed-phase HPLC step, the other on multiple HPLC runs each optimised for specific components, were used to investigate the composition of flavonoids and phenolic acids in apple and tomato juices. The principal components in apple juice were identi...
Flavonoids and monophenolic compounds have been well-described over recent years for their properties as antioxidants and scavengers of reactive oxygen and nitrogen species. A number of epidemiological studies implicate a role for flavonoids in reducing the risk of coronary heart disease. In particular, the focus has been on flavonol-rich fruit and...
Diets of individuals were supplemented with tomatoes, either cooked or as tomato pureé in order to compare uptake of lycopene from intact and homogenized fruit tissue matrices. Following a diet containing cooked tomatoes over three consecutive 7-day periods, little change in the carotenoid levels in plasma lipoproteins occurred. In contrast, a diet...
Analysis of the major flavone, flavonol, anthocyanidin and hydroxycinnamic acid constituents (and their glycosides) of onion, tomato, egg plant and apple has been undertaken and the antioxidant activities of the phenolic extracts determined. The major phenolic antioxidant components of egg plant are chlorogenic acid in the flesh and a delphinidin c...
Exposure of tyrosine or DNA bases to acidic nitrite at low pH results in the nitration of tyrosine and the formation of base deamination products, respectively. At pH 1, hypoxanthine and xanthine are formed from the deamination of adenine and guanine, respectively, whereas under the same conditions, uracil is not detected. The yield of 3-nitrotyros...
1. Dietary supplementation with vitamin E reduces ischaemic events in patients with established coronary artery disease and improves endothelial function in cholesterol-fed rabbits. We examined whether such dietary supplementation with vitamin E improves endothelial function in patients with mild hypercholesterolaemia and coronary artery disease.
2...
Oxidation of low-density lipoprotein (LDL) is of great interest for epidemiological and clinical diagnostic reasons, as well
as for basic scientific research, because it is thought to precede the development of atherosclerotic lesions (1). Measurement of individual antioxidants such as α-tocopherol, is, of course, a primary route to the study of LD...
Plasma α-tocopherol, β-carotene, serum lipids and their derived ratios were determined in British Civil Servants (n = 7177) at the second medical examination of the Whitehall II Study, a longitudinal study of cardiovascular disease. For plasma α-tocopherol the non-parametric 95% reference interval (90% confidence limits) for the total population wa...
There is currently much interest in phytochemicals as bioactive components of food. The roles of fruit, vegetables and red wine in disease prevention have been attributed, in part, to the antioxidant properties of their constituent polyphenols (vitamins E and C, and the carotenoids). Recent studies have shown that many dietary polyphenolic constitu...
This study describes evidence for the absorption of flavonoids and their presence in human plasma in the glycosylated form by HPLC analysis with photodiode array detection. Rutin and other quercetin glycosides, phloridzin, as well as an anthocyanin are detected simultaneously. In addition, a compound eluting with the spectral properties of the auro...
The aim of this work was to determine the antioxidant activities of a range of phytoestrogenic isoflavones. The antioxidant activity in the aqueous phase was determined by means of the ABTS.+ total antioxidant activity assay. The results show that the order of reactivity in scavenging the radical in the aqueous phase is genistein > daidzein = genis...
The recent explosion of interest in the bioactivity of the flavonoids of higher plants is due, at least in part, to the potential health benefits of these polyphenolic components of major dietary constituents. This review article discusses the biological properties of the flavonoids and focuses on the relationship between their antioxidant activity...
A human supplementation study was undertaken in order to investigate the correlation between the intake of individual daily dosages of vitamin E (300 mg), vitamin C (250 mg), or beta-carotene (15 mg) of eight week duration and their uptake in vivo in plasma and LDL. The effects of a combined supplement of vitamin E, vitamin C and beta-carotene (Red...
The purpose of this investigation was to establish the relative antioxidant activities in vitro of the flavanolic polyphenols, the catechins, and catechin-gallate esters. The relative antioxidant potentials were measured against radicals generated in the aqueous phase and against propagating lipid peroxyl radicals. The results show that in the aque...
In this study the antioxidant activities of the hydroxycinnamic acids, chlorogenic, caffeic, ferulic and p-coumaric have been investigated in peroxidising lipid systems mediated by metmyoglobin. The results show that the order of effectiveness in increasing the resistance of LDL to peroxidation, in protecting LDL cholesterol from oxidation and prev...
A rapid method is described for measuring the antioxidant activity of low density lipoproteins. Studies were undertaken on individuals attending a hyperlipidaemia clinic, an unsupplemented group and a group after supplementation with 300 mg dl-α-tocopherol acetate for nine weeks. The results show a positive correlation between the antioxidant activ...
Oxidation of low density lipoprotein (LDL) is implicated in the pathogenesis of atherosclerosis. In this study the susceptibility to oxidation of LDL (from patients with atherosclerosis) is related to the progression of the disease. LDL were isolated from 37 patients with demonstrable atherosclerotic plaques. The susceptibility of LDL to oxidation...
It has previously been reported that mb in both the iron-oxo ferryl and the ferric oxidation states can promote lipid peroxidation and lead to oxidative modification of low-density lipoprotein. The mechanism of these oxidation reactions is unclear and could involve either lipid hydroperoxide-dependent or independent reactions. In order to ascertain...
Quinoline and indolinone nitroxide radicals are known to be efficient scavengers of oxygen-centred (rate constants (k) between 10(3) and 10(5)/M/sec) and carbon-centred radicals (almost diffusion-controlled rate). In this study, the relative effects of these compounds in protecting low density lipoprotein (LDL) from oxidation induced by copper have...
Recent reports have detected the presence of iron in human atherosclerotic lesions [Biochem. J. 286 (1992) 901-905]. This study provides evidence for a biochemical mechanism whereby iron is released from myoglobin by low density lipoprotein (LDL) which has become oxidised by the ferryl myoglobin species. The haem destabilisation and iron release ar...
Tamoxifen and 4-hydroxytamoxifen protect isolated human low-density lipoproteins (LDLs) against copper-ion-dependent lipid peroxidation: 4-hydroxytamoxifen is more protective than tamoxifen or 17 beta-oestradiol. 4-Hydroxytamoxifen and 17 beta-oestradiol also prevent the increase in the electrophoretic mobility of LDL caused by exposure to copper i...
Low-density lipoproteins (LDL) are oxidatively modified on interaction with haem proteins. The interaction of ruptured erythrocytes with LDL induces oxidative damage as detected by alterations in electrophoretic mobility and the peroxidation of the polyunsaturated fatty acyl chains. Difference spectroscopy reveals that the amplification of the oxid...
Citations
... Taxifolin (3, 5, 7, 3, 4-pentahydroxy flavanone or dihydroquercetin, TXF) is a flavonoid found abundantly in citrus and onion [23]. Recently, the protective effects of TXF on hepatotoxicity-induced liver injury have been demonstrated [24]. Encouraging results on the renoprotective effect of TXF have been reported in a limited number of drug-induced nephrotoxicity animal models [25][26][27]. ...
... The antioxidant activities of the seaweed extracts may be linked to their bioactive constituents. Phloroglucinol, quercetin, catechin, epicatechin-3 glucoside, 3,5,7-dimethoxyflavone and biochanin A that were present in the extracts are potent antioxidants and may contribute to the observed radical and metal-chelating activities due to their ability to donate hydrogen and abstract electron (Paganga et al. 1996;Qu eguineur et al. 2012;Tatsimo et al. 2012;Viau et al. 2016). Cholinergic enzymes are very important in neurotransmission and regulate processes involved in cognitive function (Ferreira-Vieira et al. 2016). ...
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... It is a wellknown fact that phenolic compounds are constituents of many plants, and have attracted great deal of public and scientific interest because of their health promoting effects as antioxidants (Hollman and Katan, 1999). The phenolic compounds exhibit considerable free radical scavenging activities through their reactivity as hydrogen or electron donating agents, and as metal ion chelating properties (Rice-Evans et al., 1996) [20] . ...
... The high content of α-tocopherol in table olives (Malheiro et al., 2012;Sakouhi et al., 2008) reinforces the nutritional value of this product because this substance provides protection from free radicals (Cheeseeman and Slater, 1993;Kamal-Eldin and Andersson, 1997) and prevents cancer and arteriosclerosis (Armstrong et al., 1997;Caruso et al., 1997;Nicolaiew et al., 1998). Table olives are not only an important source of bioactive compounds, as described above; since they are fermented products, they are also potential functional foods as carriers of probiotic lactic acid bacteria (Argyri et al., 2013;Peres et al., 2014a). ...
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... FRAP) could not be done, and that is one of the limitations of this study. In humans, αT status has been consistently shown to be positively associated with antioxidant activity in plasma and LDL particles [43][44]. Some studies have also shown that αT supplementation, either in the form of NVE or SVE, led to lower LDL oxidation [45][46]. ...
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... Vitamin E is the major antioxidant in LDL particles, and LDL does not become oxidatively modified in vitro until the associated vitamin E is first degraded [32,33] . Supplementation of vitamin E substantially prolongs the resistance of LDL to oxidative damage [33,34] , and may have other potentially protective effects [35][36][37][38] . Beta-carotene, which can also function as a fat-soluble antioxidant in certain physiological circumstances, is carried with vitamin E in the fatty cores of the LDL particles. ...
... Redox properties of phenolic compounds act as reducing agents, hydrogen donators, and singlet oxygen quenchers. The redox potential of phenolic compounds is crucial within antioxidant potential [43]. ...
... Hence, an involvement during sugar beet storage may be possible. Ferulic acid derives from the phenylpropanoid metabolism in plants, it has antioxidant properties, and it can be incorporated into lignin [57][58][59][60] . Furthermore, it builds crosslinks between carbohydrates and lignin in plant cell walls, which confers stability [61]. ...
... The specific mechanisms underlying benefits of a healthy diet are poorly defined and although dietary supplements receive much attention within the public arena, there is a paucity of well-conducted mechanistic studies. Previous trials of vitamin C and E supplementation demonstrated conflicting effects on vascular function invivo [36][37][38][39], which may explain the negative outcome trials associated with them [40]. ...
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... Besides classical reactive oxygen metabolites, organic peroxides were shown to induce the leakage of Hb from human erythrocytes [40] and the generation of metHb [41]. FerrylHb generation was detected in the interaction between ruptured erythrocytes and LDL [42, 43]. Parallel with these findings here we showed that oxLDL but not native LDL caused Hb oxidation and subsequent covalent crosslinking of Hb subunits (Figure 4.) We found that formation of crosslinked Hb species is dose dependent, in a way that higher doses of oxLDL result in the formation of larger multimers with higher molecular weights. ...
