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Naturally occuring-antioxidants in leaf lipids
Journal of The Science of Food and Agriculture
Abstract
Lipids have been extracted from the leaves of ryegrass, broad beans and lucerne, and shown to have marked antioxidant properties as stabilisers when added to lard. The effect is due in part to natural phenolic antioxidants extracted from leaves in the lipid fraction. A series of phenolic and polyphenolic compounds have been identified and quantified in leaf lipid extract. The main ones, common to all three species, are tocopherols, ferulic acid, and quercetin. Studies of antioxidant effects in model systems have shown, on the basis of peroxide values and oxygen-absorption induction periods, that quercetin (3:5:7:3′:4′-pentahydroxy-flavone) is by far the most effective of these. It is, however, less effective under the test conditions than the artificial antioxidants BHA, BHT and propyl gallate.
... The key antioxidant enzymes possess certain elements that shield and protect proteins [10,11]. Non enzymatic antioxidants can also neutralize radicals for example water soluble substances such as Vitamin C, glutathione or fat-soluble substances such as Vitamin E, β-carotene [8,12,13]. Synthetic antioxidants such as butylated hydroxyl toluene (BHT) and butylated hydroxyl anisole (BHA) have newly been reported to be harmful for human health [14,15]. Thus, the search for effective, non-toxic, natural compounds with antioxidative activity has been increased in recent years. ...
Synthesis of nanoparticles by biological methods using microorganisms, enzymes or plant extracts has been suggested as possible ecofriendly alternative to chemical and physical methods which involve the use of harmful reducing agents. In the current study, silver nanoparticles (AgNPs) were synthesized by green approach from methanolic leaf extract of Blighia sapida . The synthesized AgNPs were characterized by UV-visible (UV-vis) spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM). The antioxidant activity was evaluated using DPPH radical scavenging assay, determination of total reductive potential, total phenolics content (TPC) and total flavonoids content (TFC) of the synthesized AgNPs. SEM analysis revealed that the size of the synthesized silver nanoparticles ranged from 50-70 nm with maximum UV-vis absorbance at 413 nm. DPPH radical scavenging activity, reducing power, total phenolic and total flavonoid contents of the synthesized AgNPs increased in a dose dependent manner as compared to ascorbic acid the standard reference used. This result confirmed that Blighia sapida is a potential biomaterial for synthesizing AgNPs which can be exploited for its antioxidant activity.
... Although dietary intake of respective tocopherols was not assessed in the current experiment, dissimilar concentrations of α-tocopherol and γtocopherol in forages versus concentrates best explains the numerically higher γtocopherol content of serum from CON steers. Corn is higher in γ-tocopherol than in αtocopherol (Hidiroglou et al., 1992;Goffman and Bohme, 2001), whereas γ-tocopherol is often less than α-tocopherol in leaf tissue (Burrows and King, 1968;Hess, 1993 (Bertram et al., 1980;Lewis, 1993 Plasma TEAC in steers is also unaltered by inclusion of PUFA in the diet , and TEAC of LM extract is not changed when cattle are finished on pasture instead of concentrates . observed cows in peak or late lactation and found that lipid hydroperoxides were more concentrated in plasma of cows in peak lactation, but that plasma TEAC was not changed. ...
... Steric hindrance would also enhance the activity, as observed with the synthetic antioxidant, butylated hydroxytoluene. The hydroxylated cinnamic acids are more eective than their benzoic acid counterparts and activity becomes marked in caeic and chlorogenic acids (Hudson & Mahgoub, 1980). Orthosubstitution with electron-donating alkyl or methoxy groups increases the stability of the aryloxyl radical and hence its antioxidant potential . ...
Phenolic compounds occur in all fruits as a diverse group of secondary metabolites. Hence, they are a component of the human diet although data for dietary intakes and metabolic fate are limited. Their role in oxidation processes, as either antioxidants or substrates in browning reactions, is examined. They are characterised by high chemical reactivity and this complicates their analysis.
... Flavonols have been a subject of increasing research concerning their potency for use as natural antioxidants in food systems. Early studies (Hudson and Mahgoub, 1980) showed that flavonols such as quercetin, kaempferol, and rutin exhibit good stabilizing activity when added to lard as leaf lipid extracts. Quercetin and myricetin were also found to efficiently inhibit oxidation of ground fish lipids (Ramanathan and Das, 1992). ...
The oxidative degradation of quercetin and rutin in phosphate buffer solutions, pH 8.0, at 97 degrees C, was studied by means of UV-vis spectroscopy and reversed-phase high-performance liquid chromatography (HPLC). The effect of the transition metal ions Fe(2+) and Cu(2+) On degradation rate and browning development was also assessed. It was shown that both flavonols are very labile to thermally induced degradation under oxidative conditions. Fe(2+) and Cu(2+) caused an increase in the degradation rate, as well as an increase in browning (A(420)) Significant differences were observed in the degradation mechanisms, as implied by HPLC analyses. It is postulated that metal ions promote flavonol oxidation through reactive oxygen species formation, whereas increases in browning could be ascribed to oxidation and metal-polyphenol interactions.
... As regards oleuropein, its antioxidant activity is mainly due to the hydroxytyrosol moiety in its structure (Benavente-Garcia et al., 2000). The hydroxylated cinnamic acids are more effective than their benzoic acid counterparts and the activity becomes marked in caffeic and chlorogenic acids (Hudson & Mahgoub, 1980). The evaluation of the oxidative stability of commercial virgin olive oil and sunflower oil enriched with phenol extracts of olive oil mill waste, by the determination of peroxide value, is presented in Table 4. ...
Olive oil mill waste was subjected to conventional liquid solvent extraction and supercritical fluid extraction using different solvents and carbon dioxide, respectively. The optimum solvent extraction conditions of phenols were 180min using ethanol, at a solvent to sample ratio 5:1 v/w, and at pH 2. Solvent and SFE extracts were tested for their antioxidant activity by the DPPH radical scavenging method and by determination of peroxide value on virgin olive oil and sunflower oil. The ethanol extract exhibited the highest antiradical activity, and no correlation was found between antiradical activity and phenol content. The SFE extract exerted good antioxidant capacity although its phenolic yield was not quite high. Moreover, the ethanol extract appeared to be a stronger antioxidant than BHT, ascorbyl palmitate and vitamin E by the Rancimat method on sunflower oil. HPLC analysis of the extracts showed that the predominant phenolic compound was hydroxytyrosol. Various phenolic acids and flavonoids were also identified.
... The flavonols quercetin and myricetin efficiently inhibit lipid oxidation (16,17) and are considered to be better antioxidants then butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) (18,19). These flavonols are extremely hydrophobic and despite their wide potential health benefits, their use in fuctional foods is limited by their low solubility in water. ...
The in vitro formation of quercetin− and myricetin−cyclodextrin inclusion complexes in acidic medium has been characterized using the enzymatic system horseradish peroxidase, which oxidizes those flavonols in the presence of H 2O 2. The presence of cyclodextrins (CDs) in the reaction medium inhibited flavonol oxidation due to the complexation of the flavonol in the hydrophobic cavity of CDs. This inhibitory effect depends on the complexation constant K c between flavonol and the CD type used. The K c for quercetin and myricetin with the different types of CD used was calculated by nonlinear regression of the inhibition curves obtained in the presence of CDs. In both cases (quercetin and myricetin), the K c values obtained followed the order hydroxypropyl-β-CDs > maltosyl-β-CDs > β-CDs, reflecting the greater affinity of modified cyclodextrins for the studied flavonols compared with their parental β-CDs. Moreover, the complexation efficiency (CE) values for HP-β-CDs and quercetin or myricetin were calculated (267.4 and 5.3, respectively), indicating that HP-β-CDs are more efficient for the complexation of quercetin than myricetin in the studied conditions, despite of the K c values being very similar in both cases. Keywords: Quercetin; myricetin; cyclodextrin; enzymatic method; complexation constant
Two ferrocenyl derivatives, Fc-CA and Fc-FA, were synthesized by a condensation reaction between the amino ferrocene and hydroxycinnamic acids, that is, caffeic acid (CA) and ferulic acid (FA). The structures and purity of all compounds were characterized by 1H- A nd 13C NMR spectroscopies, Mass spectrometry (MS), and elemental analysis. The antioxidant properties of Fc-CA and Fc-FA and of its ligand were studied for free radical scavenging activity toward DPPHâ, superoxide anion (O2â-), NOâ, and ABTSâ+ by UV-vis and electron spin resonance spectroscopies. The cytotoxicity of Fc-CA and Fc-FA against MCF-7 and MDA-MB-231 breast cancer cells and MRC-5 human lung fibroblasts cell was higher than that of cisplatin. The geometry and electronic structures of all compounds were then simulated using density functional theory at M05-2X/6-311+G(d,p) level of theory. Thermodynamics of the free radical quenching reactions by common mechanisms reveal the higher antioxidant properties of the Fc-CA and Fc-FA in comparison to their ligands. An in-depth study of the free radical scavenging activity against HOOâ and HOâ radicals was performed for two of the most favorable and competitive mechanisms, the hydrogen transfer (either hydrogen atom transfer or proton-coupled electron transfer mechanisms) and the radical adduct formation. The in silico studies indicated that ferrocenyl derivatives exhibited prominent binding affinity to protein models in comparison to CA and FA. Their dock scores were notable at ligand binding sites of ERα, Erβ, and JAK2 proteins. Dock pose analysis also shed light into the possible mechanism of action for the studied compounds.
Two ferrocenyl derivatives, Fc-CA and Fc-FA, were synthesized by a condensation reaction between the amino ferrocene and hydroxycinnamic acids, that is, caffeic acid (CA) and ferulic acid (FA). The structures and purity of all compounds were characterized by 1H- and 13C NMR spectroscopies, Mass spectrometry (MS), and elemental analysis. The antioxidant properties of Fc-CA and Fc-FA and of its ligand were studied for free radical scavenging activity toward DPPH•, superoxide anion (O2•–), NO•, and ABTS•+ by UV–vis and electron spin resonance spectroscopies. The cytotoxicity of Fc-CA and Fc-FA against MCF-7 and MDA-MB-231 breast cancer cells and MRC-5 human lung fibroblasts cell was higher than that of cisplatin. The geometry and electronic structures of all compounds were then simulated using density functional theory at M05-2X/6-311+G(d,p) level of theory. Thermodynamics of the free radical quenching reactions by common mechanisms reveal the higher antioxidant properties of the Fc-CA and Fc-FA in comparison to their ligands. An in-depth study of the free radical scavenging activity against HOO• and HO• radicals was performed for two of the most favorable and competitive mechanisms, the hydrogen transfer (either hydrogen atom transfer or proton-coupled electron transfer mechanisms) and the radical adduct formation. The in silico studies indicated that ferrocenyl derivatives exhibited prominent binding affinity to protein models in comparison to CA and FA. Their dock scores were notable at ligand binding sites of ERα, Erβ, and JAK2 proteins. Dock pose analysis also shed light into the possible mechanism of action for the studied compounds.
A 60-week long storage experiment was conducted to determine carotenoid stability on freeze-dried alfalfa (c.v. Natsuwakaba) leaf extract treated with various antioxidants during herbage processing. The antioxidants used were ethoxyquin (ETX), sodium metabisulfite (MBS), butylated hydroxyanisole (BHA), ascorbic acid (AA), α-tocopherol (AT) and tea leaf extract (TLE). Each leaf extract was divided into six portions and allocated into 2 clear and 4 amber coloured glass jars. One clear and 2 amber jars were flushed with nitrogen gas while ordinary air head space prevailed in the other three jars. The amber jars were kept under two storage shemes ; (a) 12-h constant lighting provided by 16 pieces of 40W fluorescent lamps with temperature controlled at 28℃ and (b) in a freezer (-18℃) without exposure to light. The clear jars were kept only under storage scheme (a). Low temperature protected the xanthophylls regardless of treatments of antioxidants but did not protect effectively β-carotene without ETX under long-term storage. At 28℃, both β-carotene and xanthophylls were degraded but the rate was far reduced by treating with ETX and keeping in amber coloured jars. With these treatments, about two-thirds of the values at 6-week storage were recovered after 60 weeks. Nitrogen gas flushing had no significant effect. Butylated hydroxyanisole, MBS and TLE could be alternative antioxidants but only for short-term storage. α-Tocopherol and AA did not prevent the decomposition of carotenoid at all. The study showed that addition of ETX during herbage processing and storing the leaf extract at low temperature (-18℃) gave the best protection for carotenoids. The best protein yield was also obtained in ETX treated leaf extract.
Whether concern is directed towards the needs of a less-developed country with a food shortage, the problems of a country where there is a surplus of grain while fishmeal and oilseed residues are imported as feed for pigs and poultry, or towards the more general matter of making farming more efficient, protein extracted from leaves (LP) deserves attention. There are many reasons for this, for example:
1.
Leaves are the primary site of protein synthesis and protein is lost when translocated to seeds or tubers.
2.
Suitable crops maintain a photosynthetically active cover throughout the period in which growth is possible. Yields are therefore greater than with any other type of crop. LP is therefore potentially the most abundant source of protein. Conventional leafy vegetables share this merit. Increased use of them would be advantageous, but the amount of fibre which accompanies the protein in them sets a limit to consumption.
3.
Ruminants return as human food only 5 to 30% of the protein they eat, whereas 50 to 60% of the protein in a leaf crop can be extracted.
4.
Species rejected as human or animal food because of texture or toxicity can be used as LP sources. When the LP is washed, flavour and toxic material are usually removed. Ruminants readily eat the extracted residue and do well on it, because, coming from young plants, it is less lignified than a crop which, untreated, has the same N content. Because it has been pressed, there is no drip when it is ensiled, and less fuel is needed than with a normal crop to dry it completely for use as winter feed.
5.
If made carefully, LP is nutritionally better than the usual seed proteins; but not as good as egg or milk. Like other proteins which contain carbohydrates and unsaturated fats, it is damaged by inept handling.
6.
Extraction equipment can be simple enough for use in villages; equipment for large-scale extraction has also been designed.
7.
People with European or North American prejudices find the appearance of LP unusual at first. They soon accept it, and no problems with acceptance have been met anywhere where it has been intelligently presented.
Reports in recent years both in the popular and scientific press have stressed the value and advantages of natural ingredients as food preservatives. There is an implied assumption of safety for compounds that occur naturally in foods and that have been consumed for many centuries. It is not the intent of the authors to debate the issue of superiority of either natural or synthetic food components as to the safety or functional properties. It is preferable, however, to use substances that do not pose problems of proof of safety. Caution should be employed in the use of natural compounds: except for the major commercial synthetic versions (tocopherols, ascorbic acid) they have not usually been subjected to scrutiny and scientific evaluation as have the artificial synthetic compounds (BHA, BHT). Their potential as mutagens, carcinogens, teratogens, or as other pathogens must be investigated.
Avocado lipoxygenase activity increased from 20 to 40 μmole O2 h−1 g−1 fresh weight of peel in unripe fruits during the first hour after harvest, and in ripening fruits 4 to 5 days after harvest. Concomitantly, the concentration of the antifungal compound cis, cis-1-acetoxy-2-hydroxy-4-oxo-heneicosa-12, 15-diene decreased from approx. 1700 to 200 μg g−1 fresh weight of peel. The concentration of epicatechin in the peel was inversely correlated with lipoxygenase activity in each case, and decreased significantly when lipoxygenase increased. The amount of lipoxygenase in the crude extract of the fruit peel during ripening, which was determined by the ELISA technique, ranged between 10 and 30 μg g− fresh weight of peel during ripening, and was not correlated with the changes in the enzyme activity.The results suggest that the differences in lipoxygenase activity are not correlated with changes in the amount of this enzyme, but rather result from changes in the concentrations of its inhibitor, epicatechin.
This paper is limited to those catalysts and lipid oxidation inhibitors which have been found to be present either in the raw food materials or in processed food as a result of its processing.Lipoxygenase and haemoproteins are very powerful lipid oxidation catalysts in many foods. Heat treatment usually inactivates lipoxygenase but can, under certain conditions, activate haemoproteins as non-enzymatic metal catalysts. Tocopherol, normally referred to as an antioxidant, can, under certain concentration conditions, shift to pro-oxidative properties. Even volatile lipid oxidation products have been shown to accelerate lipid oxidation.Inhibitors present in raw materials are found among proteins, amino acids and plant constituents such as flavonoids. Most spices and herbs have antioxidative properties, particularly in darkness. Some microorganisms in their normal metabolism inhibit lipid oxidation or the consequences thereof. Some enzymes, especially superoxide dismutase, are claimed to inhibit lipid oxidation. Among process-induced lipid oxidation inhibitors, Maillard reaction products are those most investigated, together with protein hydrolysates. Smoking generates antioxidative compounds. In most cases the mechanism of lipid oxidation inhibition is still unknown for these materials.
The effects of minor-component phospholipids, sterols, trimethylamine oxide (TMAO) and tri-n-octylamine (TOA) on the stabilization
of γ-tocopherol (γ-Toc) were investigated during the autoxidation of methyl linoleate (ML). On autoxidation of lard containing
γ-Toc and TMAO, γ-Toc was rapidly oxidized and decreased to the 50–60% level in the initial stage of reaction. After that,
the total amounts of γ-Toc and its reducing dimers, γ-Toc diphenyl ether dimer, γ-Toc biphenyl dimer (H), and γ-Toc biphenyl
dimer (L), formed from oxidized γ-Toc, were maintained at a higher level for a longer time. These results indicate the presence
of minor components contribution to the stability of γ-Toc. Therefore, three-component synergism involving γ-Toc, TMAO and
each phospholipid was tested using ML as substrate. Accordingly, phosphatidyl ethanolamine (PE), phosphatidyl serine (PS),
phosphatidyl inositol and phosphatidic acid showed a marked synergistic effect: PS especially inhibited the oxidation of γ-Toc.
More than 0.02% of PE was found to keep a constant level of the residual amount of γ-Toc and to retared the formation of γ-Toc
biphenyl dimers, which are perferential in the presence of TMAO. Phosphatidyl choline (PC), phosphatidyl glycerol and sterols
did not show such an effect. However, PC synergized with TOA for stabilizing γ-Toc in autoxidizing ML.
The effects of several flavonoids and other known antioxidants on the thermal autoxidation of refined, bleached and deodorized (RBD)-palm oil were studied. The lipid peroxidation was indexed by measuring the malonyldialdehyde (MDA) production using the 2-thiobarbituric acid (TBA) test. The antioxidative action decreased in the order of morin > kaempferol > myricetin > quercetin > vitamin A > α-tocopherol > apigenin > (+)-catechin > chrysin > datiscetin > luteolin > naringin > taxifolin > rutin > butylated hydroxytoluene (BHT) > naringenin.
The flavonoid aglycones were more potent in their antiperoxidative action than their corresponding glycosides. Structure-activity revealed that the flavonoid molecule with polyhydroxylated substitutions on rings A and B, a 2–3 double bond, a free 3-hydroxyl substitution and a 4-keto moiety, would confer potent antiperoxidative properties upon the compound. The flavonols, namely morin, myricetin, kaempferol and quercetin, would be suitable potential antioxidants for use in the stabilization of RBD-palm oil and its fractions against thermal autoxidation. The structural activity of the flavonoids on the RBD-palm oil was similar to those observed for these compounds in animal tissue or enzyme systems.
The protective effect of the polyhydroxyflavones Fisetin and Baicalein on the sensitized [O2(¹δg] - mediated photooxidation of fats was investigated through a kinetic study. These flavonoids at concentrations in the order of a few ppm efficiently inhibit the photoperoxidation of linoleic acid, which was chosen as an example of photooxidizable fat. This property was attributed to the ability of Fisetin and Baicalein to quench photochemically generated O2(¹δg). The rate constants for such a process of quenching were 1.9 and 1.4 × 10⁸ M⁻¹S⁻¹ for Fisetin and Baicalein respectively. The ratio between the overall and the chemical rate constants were in the order of 0.01, indicating that the flavones are practically not consumed in the process of O2(¹δg) quenching. The presence of the -OH groups in the aromatic rings of the hydroxyflavones confer to these compounds the ability as O2(¹δg) quenchers. The parent compound Flavone does not quench that oxygen excited species. Only Flavone generates O2(¹δg) upon direct irradiation, at 337 nm, in the absence of added sensitizers, with a quantum yield of 0.16. Fisetin and Baicalein were totally inefficient for such a process. This fact constitutes a very convenient property from the point of view of the protective (anti oxidative) activity of the hydroxyflavones.
The antioxidant activity of a number of flavonoids in refined-bleached (RB) canola (double-zero rapeseed) oil is compared with that of commonly used synthetic antioxidants, namely, butylated hydroxyanisole, BHA, and butylated hydroxytoluene, BHT. The study was carried out over a thirteen-day period at 65°C and progression of oxidation was followed by monitoring weight gain and peroxide and 2-thiobarbituric acid (TBA) values. Among the flavonoids tested, myricetin, (−)epicatechin, naringin, rutin, morin, and quercetin were superior to BHA and BHT in inhibiting oil oxidation. The addition of myricetin, the most active flavonoid tested, delayed the induction period of lipid oxidation by up to fifteen days and also inhibited the formation of oxidation products by 69% during this period. Natural flavonoids may therefore have potential application for the stabilization of canola oil.
The pro-oxidant effect of copper in lard, as judged by the development of peroxide values and the shortening of induction periods, can be counteracted by quercetin but not by BHT. On a molar basis, between 100 and 1000 times as much quercetin as copper is required for complete inhibition of the copper. This is evidence that a weak chelate is formed between quercetin and cupric ions in the oil medium.
The antioxidative properties of native flours derived from three types of faba beans in different concentrations, as well as flours from dehulled soybeans and oats without husk, were determined using the Schaal oven test. The antioxidative potential was expressed by the protection factor against the oxidation of lard or sunflower oil. All three raw materials showed pronounced antioxidative potential, but native flour from oats had an exceptionally strong antioxidative effect. Although steaming of all three flours reduced their antioxidative potential, it was most detrimental to oat flour. Tempeh fermentation increased the antioxidative effects in all three raw materials, where the highest increase was obtained with flour derived from faba beans. The influence of conditions of fermentation on the antioxidative activity was also tested during the production of tempeh from oats. Fermentation time, as well as the water/oat flour ratio, were found to have a highly significant influence (P < 0.01).
Caffeic acid (CA) has been implied as an important source of natural antioxidants in various agricultural products. We compared the antioxidative activity of CA and dihydrocaffeic acid (HCA) in lard and the low-density lipoprotein (LDL) system to know the role of the 2,3-double bond on the appearance of its antioxidative property. HCA was more effective than CA in enhancing oxidative stability of lard at 60 °C. Inhibition by HCA of copper ion-induced oxidation of human LDL was less effective than that by CA, whereas there was no significant difference between the two compounds in the capacity of 1,1-diphenyl-2-picrylhydrazyl radical scavenging and the activity of lipid peroxyl radical scavenging in solution. It can be concluded that the 2,3-double bond in the structure of CA affects the efficiency of antioxidative activity depending on the environment where the oxidation happens, although it is rarely responsible for its inherent activity. Keywords: Antioxidants; caffeic acid; dihydrocaffeic acid; free radical-scavenging activity; low-density lipoprotein
Carotene and xanthophyll are valuable constituents of alfalfa leaf protein concentrate (Pro-Xan), which is now prepared commercially. The effects of moisture content, pH, pelleting, inert atmosphere storage, and the addition of an antioxidant, fat, or alfalfa-soluble solids on the storage stability of these carotenoids were investigated. Earlier work on storage at low temperatures and in the dark is discussed. Greatest stability is obtained by addition of the antioxidant ethoxyquin (0.05%), storage in an inert atmosphere, and, if economically feasible, cold storage. Increases in stability, particularly of carotene, are also obtained by drying to a lower moisture content, addition of fat, or addition of the soluble solids remaining after separation of the alfalfa protein. It is essential that any added fat be stabilized with antioxidants and free of peroxides that promote the oxidation and destruction of carotenoids.
Based on oxygen absorption induction periods, the phospholipids, phosphatidylcholine and phosphatidylethanolamine, have been shown to exert a deleterious effect on the stability of lard. However, when these phospholipids are used in combination with the naturally-occurring antioxidants, α-tocopherol and/or quercetin, a very substantial improvement in oxidative stability can be observed. This form of synergistic interaction has been shown to account for the remarkable stability exhibited by leaf lipids.
Antioxidant activity of a number of flavonoids in refined-bleached and deodorized (RBD) seal blubber oil (SBO) and menhaden oil (MHO) was compared with that of commercially used antioxidants, namely butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ) as well as -tocopherol. The study was carried under Schaal oven conditions at 65C and progression of oxidation was followed by monitoring weight gain, peroxide value (PV) and 2-thiobarbituric acid reactive substances (TBARS) value. Among the flavonoids tested in this study, the flavonols, namely myricetin, quercetin and morin exhibited a stronger antioxidant activity than BHA and BHT and effectively stabilized both SBO and MHO. Myricetin was the most effective flavonoid tested in this study and its effect in reducing lipid oxidation was similar to that of TBHQ.
The effectiveness of α-tocopherol, two flavonoids (quercetin and ru-tinic acid) and a cinnamic acid (chlorogenic acid) as inhibitors of peroxidase was evaluated. Four concentrations, 125, 250, 500 and 1000 mg%, of each compound were used. Crude extracts of tomatoes, carrots and eggplant were the sources of enzyme activity. Peroxidase activity of carrots and eggplant was inhibited more than that of tomato by all antioxidants. Alpha-tocopherol was least effective in all systems and at all concentrations. Chlorogenic acid was most effective, followed by quercetin and rutinic acid.
The antioxidant properties of a series of polyhydroxy flavonoids and related compounds have been evaluated. The results have been correlated with the structures of the compounds concerned, which hale been shown to Junction mainly as primary antioxidants. The ability of some such compounds to form complexes with copper has been demonstrated from a study of UV spectra and is probably a contributing factor to the stabilising effects of such compounds.Antioxidant activity is favoured by a multiplicity of phenolic hydroxyl groups and depends critically on the co-operation of the 4-carbonyl with either the 3- or the 5-hydroxyl groups. Dihydro-flavones are slightly more active than the corresponding flavones.
The antioxidant properties of freeze-dried citrus fruit peels (orange, lemon, grapefruit) and methanolic extracts from the peel were studied. Freeze-dried orange peel showed the highest, lemon peel somewhat less and grapefruit peel the lowest but still remarkable antioxidant activity. This could be significantly improved by preparing methanolic extracts of the peels. Comparative examinations and autoxidation studies with the flavanon glycosides hesperidin and naringin as well as with their aglycones hesperetin and naringenin showed that the former are mainly responsible for the antioxidant activity of the citrus peel and extracts. In order to compare their antioxidative activity with that of the commercially available natural antioxidants α-tocopherol and ascorbylpalmitate, the freeze-dried citrus peels and their methanolic extracts should be used in higher concentrations, in consideration of their peculiar properties and complex natural composition. Furthermore, aspects of the correlation between antioxidant activity and molecular structure of the flavanones were discussed.
Methanol extraction of hulls from Tainan select no. 9 (P-9) and Tainan no. 11 (P-11) peanuts produced a higher yield of a
component having stronger antioxidant activity (AOA) than other organic solvents. The AOA of methanolic extracts from peanut
hulls was equal to butylated hydroxyanisole and stronger thanα-tocopherol. The methanolic extract from peanut (P-11) hulls was separated into 18 fractions by thin-layer chromatography
(TLC). High antioxidant activity was found in subfractions with Rfs of 0.20, 0.25, 0.28, 0.31 and 0.37 at 95.6%, 93.8%, 94.7%, 92.0% and 81.6% inhibition of peroxidation of linoleic acid,
respectively. Further purification of the subfraction eluting at 0.20 yielded a compound with antioxidant activity of 94.8%.
Based on high-performance liquid chromatography (HPLC) analysis, ultraviolet (UV) spectra and1H nuclear magnetic resonance (NMR), this compound was identified as luteolin.
Antioxidative properties ofp-hydroxybenzoic, vanillic, syringic, 3,4-dihydroxybenzoic,p-coumaric, ferulic, sinapic and caffeic acids were studied in the concentration range 0.02–0.20 wt% during autoxidation at
100°C of lard and sunflower oil methyl esters (MEL and MESO, respectively). In both lipid systems, the derivatives of benzoic
acid had weaker inhibiting properties than did the corresponding analogues of cinnamic acid. The effectiveness and strength
of the antioxidative action were considerably lower in the lipid system MESO, which was rich in linoleic acid and was more
easily oxidized. Thep-hydroxybenzoic, vanillic, syringic andp-coumaric acids in this system exercised no inhibiting effect. We established that the molecules of the investigated phenolic
acids initiated the chain radical process of autoxidation, and the formed antioxidant radicals propagated the chains as a
result of the reaction with the lipid substrate. These reactions proceeded at a higher rate in MESO than in MEL.
Antioxidant activities of almond whole seed, brown skin, and green shell cover extracts, at 100 and 200 ppm quercetin equivalents,
were evaluated using a cooked comminuted pork model, a β-carotene-linoleate model, and a bulk stripped corn oil system. Retention
of β-carotene in a β-carotene-linoleate model system by almond whole seed, brown skin, and green shell cover extracts was
84–96, 74–83, and 71–93%, respectively. In a bulk stripped corn oil system, green shell cover extract performed better than
brown skin and whole seed extracts in inhibiting the formation of both primary and secondary oxidation products. In a cooked
comminuted pork model system, green shell cover and brown skin extracts inhibited the formation of TBARS, total volatiles,
and hexanal more effectively than did the whole seed extract. HPLC analysis revealed the presence of caffeic, ferulic, p-coumaric, and sinapic acids as the major phenolic acids in all three almond extracts examined.
Oregano (Origanum vulgare L.) leaves were successively extracted with hexane, ethyl ether, ethyl acetate and ethanol. The ethanol extract was reextracted
in a separatory funnel with petroleum ether, ethyl ether, ethyl acetate and butanol. The ethyl ether layer was the most effective
in stabilizing lard against oxidation, with activity equal to butylated hydroxytoluene. It also showed antioxidant activity
when tested on vegetable oils under storage or frying conditions. The main antioxidant factors isolated from the ethyl ether
layer consisted of flavonoids. Chromatographic and spectrophotometric analysis demonstrated the presence of the flavone apigenin,
the flavanone, eriodictyol and the dihydroflavonols, dihydrokaempferol and dihydroquercetin.
The use of natural antioxidants to improve the oxidative stability of food lipids has received special attention because of the worlwide trend to avoid the use of synthetic food additives. The efficacy of natural antioxidants and the oxidative stability of edible oils and food emulsions have been difficult to evaluate in view of questionable conditions and methodology used to follow oxidation. The methodology used to evaluate natural antioxidants must be carefully interpreted depending on the conditions of oxidation and the analytical method used to determine the extent and endpoint of oxidation. The purpose of this review is to re-evaluate current methods of determining the oxidative stability of food lipids and the effectiveness of natural antioxidants.
The synergistic effects of phosphatidyl ethanolamine and phosphatidyl choline in enhancing the antioxidant properties of some polyhydroxy flavonoids in lard at 100–140°C have been investigated. Phosphatidyl ethanolamine is very effective in all cases, especially when used at concentrations upwards of 0·1%, with flavonoids at levels of 0·007% to 0·07%. Phosphatidyl choline has little synergistic activity.Possible causes of the synergism are discussed. It is concluded that the presence in the synergist molecule of a strongly acid, proton generating function is of importance.
The progressive accumulation of beta-amyloid peptide (Abeta), in the form of senile plaques, has been recognized as one of the major causes of Alzheimer's disease (AD) pathology. Increased production of Abeta and the aggregation of Abeta to oligomers have been reported to trigger neurotoxicity, oxidative damage and inflammation. Furthermore, Abeta-induced tau hyperphosphorylation and neurotoxicity are downstream of Abeta. Therefore, we studied the possible neuroprotective effects of caffeic acid against Abeta-induced toxicity.
Treatment of PC12 cells with 10 microM Abeta (25-35) for 24 h significantly decreased the cell viability; this was accompanied by an increase in intracellular calcium levels and tau phosphorylation with GSK-3beta (glycogen synthase kinase-3beta) activation (phosphorylation).
However, pretreatment of the PC12 cells with 10 and 20 microg/ml of caffeic acid, for 1 h prior to Abeta, significantly reversed the Abeta-induced neurotoxicity by attenuating the elevation of intracellular calcium levels and tau phosphorylation.
Taken together, these results suggest that caffeic acid protected the PC12 cells against Abeta-induced toxicity. In addition, the neuroprotective mechanisms of caffeic acid against Abeta attenuated intracellular calcium influx and decreased tau phosphorylation by the reduction of GSK-3beta activation.
Ferulic acid is a ubiquitous plant constituent that arises from the metabolism of phenylalanine and tyrosine. It occurs primarily in seeds and leaves both in its free form and covalently linked to lignin and other biopolymers. Due to its phenolic nucleus and an extended side chain conjugation, it readily forms a resonance stabilized phenoxy radical which accounts for its potent antioxidant potential. UV absorption by ferulic acid catalyzes stable phenoxy radical formation and thereby potentiates its ability to terminate free radical chain reactions. By virtue of effectively scavenging deleterious radicals and suppressing radiation-induced oxidative reactions, ferulic acid may serve an important antioxidant function in preserving physiological integrity of cells exposed to both air and impinging UV radiation. Similar photoprotection is afforded to skin by ferulic acid dissolved in cosmetic lotions. Its addition to foods inhibits lipid peroxidation and subsequent oxidative spoilage. By the same mechanism ferulic acid may protect against various inflammatory diseases. A number of other industrial applications are based on the antioxidant potential of ferulic acid.
This chapter presents the ubiquitous nature and pervasiveness of lipid oxidation ex vivo in foods and in vivo, and demonstrates that oxidation generally has deleterious results in both systems. This dramatizes the need for more effective strategies for controlling lipid oxidation, both in food materials and in tissues in vivo. The chapter discusses the existing practices using antioxidants, chelators, enzyme inactivation, and anoxic and low-temperature storage conditions. The oxidative degradation of the unsaturated fatty acid components of food lipids may be beneficial in some foods in generating low levels of desirable flavorful carbonyl compounds. However, in general, oxidation causes deleterious changes in flavor, taste, color, texture, and possibly safety of foods. The polyunsaturated fatty acids (PUFA)—particularly the trienoic, pentaenoic, and hexaenoic PUFA commonly found in oilseeds and seafoods—render these foods, which are particularly sensitive to oxidative changes which limit their self-life.
This review assembled literature data on the distribution of flavonoid compounds (FC) among food plants as well as data on the antioxidative activity (AOA) as related to structure and pharmacologic action. Special attention was accorded to the problem of the use of FC as exergonic food antioxidants FC are not xenogenic to humans and are distinguished by their low (or completely absent) toxicity. Their AOA, as a rule, is superior to that of known antioxidants. The possible, eventual augmentation of wholesome medically prophylactic properties of essential food products by regulated addition of FC was discussed. The benefit of the use of specific additives-quercetin and dihydroquercetin-compared to the utilization of mixed plant SC was demonstrated. Medically prophylactic food products, with supplementation of FC, are devised for regions with unfavorable ecologic circumstances (increased radioactivity, contaminated industrial effluents) as well as for regions susceptible to the influence of stress factors or extreme climatic conditions.
Although an antioxidant mechanism has been involved in the beneficial effects of ferulic acid in human diseases, there are few reports on the antioxidant properties of this compound in isolated membranes and intact cells. Here, we evaluated the ability of ferulic acid in inhibiting lipid peroxidation in rat liver microsomal membranes and reactive oxygen species production in NIH-3T3 fibroblasts, induced by both tert-BOOH and AAPH. We also compared its antioxidant efficiency with that of other antioxidants, such as alpha-tocopherol, beta-carotene, and ascorbic acid, added alone or in combination. Ferulic acid acted as a potent antioxidant in our models, being more effective in protecting from tert-BOOH than from AAPH. Moreover, the compound was the most effective among the antioxidants tested. Synergistic interactions were observed when the compound was used in combination with the other antioxidants, suggesting that they can cooperate in preserving physiological integrity of cells exposed to free radicals.
Polyphenols are widely distributed in various fruits, vegetables and seasonings. It is well known that they have several physiological effects due to their antioxidative activities. Their activities depend on structural characteristics that favour the formation of their corresponding stable radicals. During the examination at which pH values, the polyphenol radicals are stabilized, we confirmed that polyphenol radicals were stabilized in NaHCO3/Na2CO3 buffer (pH 10) rather than in physiological pH region. Then, we measured electron spin resonance (ESR) spectra at pH 10 to examine the characteristics of free radical species derived from caffeic acid (CA) with an unsaturated side chain, dihydrocaffeic acid (DCA) with a saturated side chain, chlorogenic acid (ChA) and rosmarinic acid (RA). In analyzing the radical structures, ESR simulation, determinations of macroscopic and microscopic acid dissociation constants and molecular orbital (MO) calculation were performed. In CA, the monophenolate forms were assumed to participate in the formation of free radical species, while in DCA, the diphenol form and the monophenolate forms were presumed to contribute to the formation of free radical species. On the basis of the results, we propose the possible structures of the free radical species formed from polyphenols under alkaline conditions.
Dynamics of population mutagenesis during 22 consecutive generations of animals, as well as genetic radioadaptation were studied in natural populations of small mammals (bank voles) under chronic low-intensive irradiation due to the Chernobyl accident. The data obtained point to oppositely directed processes in irradiated populations: accumulation of mutations (genetic load of populations) and formation of genetic radioadaptation. It is suggested that the frequencies of genetic damages in populations could be higher in the absence of radioadaptation process. A relationship between the frequencies of cytogenetic injuries and low doses of radiation was revealed in animal generations studied. The non-linear dose-effect curves are most likely to be defined by the complicated microevolutionary processes in populations. The results obtained indicate the absence of genetic effect threshold of low dose radiation. Besides, they show that a dependence of cytogenetic effects on radiation low doses in series of irradiated generations cannot be revealed using linear equations.
The term flavonoid is generally used to denote the group of plant phenols characterized by the carbon skeleton C6-C3-C6. The basic structure of these compounds consists of two aromatic rings linked by a three carbon aliphatic chain which normally has been condensed to form a pyran or less commonly a furan ring. As the name implies flavone may be considered the general type compound of the flavonoid group. Based chiefly on the oxidation state of the aliphatic fragment, these compounds may be subdivided into several groups (1, 2, 3). The widest and most inclusive classification (2) places the flavonoids into three classes: 1) The anthoxanthins include all flavonoids that possess a carbonyl group in the 4-position. The center condensed ring may be either the pyran or furan structure; or in one case (the chalcones) the alphatic fragment is not condensed into a ring. 2) The flavans include flavonoids that do
The lipids of leaf protein concentrate show a high degree of resistance to autoxidation. Oxygen absorption studies show that very long induction periods operate for various lipid fractions. A close relationship exists between oxidative attack on α-linolenic acid and induction period, except when a more readily oxidised component, e.g. carotenoid, is also present, when the induction period corresponds to the degradation of such a component in preference to that of α-linolenic acid. The explanation for the unexpected stability of the lipids from leaf protein concentrate is believed to lie in the presence of very potent antioxidants whose nature remains to be elucidated.
Seven chemical methods, namely peroxide value (PV), totox value (TV), anisidine value (AV), conjugable oxidation products (COP), oxodiene value (OV), induction period (IP), iodine value (IV) and a sensory analytical procedure (flavour score, FS) have been used in evaluating the oxidation state of groundnut oil heated at 100°C for varying lengths of time up to 20 h. As oxidation progressed, PV, TV, AV, COP and OV increased. IP and IV decreased with oxidation while FS showed a progressive deterioration on a seven-point scale from bland to very rancid. On the basis of sensitivity to oxidative changes, five of the methods (PV, TV, IP, IV and FS) were found to be satisfactory. However, the best correlation with flavour scores were obtained in the case of IP, IV and OV while AV and COP correlated poorly with FS. Three methods (PV, IP and IV) best satisfied the combined criteria of sensitivity to oxidative changes and correlation with flavour.
In this review the qualitative and quantitative occurrence of flavonols and flavones, particularly in fruit and vegetables, are considered. They occur practically in all plants. Their formation normally depends on light so that they are mainly concentrated in the outer tissues. the concentration of flavonols in free standing leaves exceeds that in other parts of the same plant considerably, except in onions.
Flavonols act as antioxidants and protect the ascorbic acid from auto‐oxidation, for example in fruit juices. On the other hand, flavonols can lead to discolourations. Beneficial effects on the human organism have also been described.