Antioxidative activity of green tea catechin extract compared with that of rosemary extract

This study compared the antioxidative activity of green tea catechin (GTC) extract with that of rosemary extract in canola oil, pork lard, and chicken fat. The GTC extract was obtained from jasmine and longjing green teas and mainly consisted of four epicatechin isomers including (−)epigallocatechin gallate (EGCG), (−)epigallocatechin (EGC), (−)epicatechin (EC), and (−)epicatechin gallate (ECG). The oxidation was conducted at 100 ± 2°C by monitoring oxygen uptake. The oxygen consumption test demonstrated that GTC extract was much more effective than the rosemary extract against lipid oxidation in canola oil, pork lard, and chicken fat under the conditions of the present study. Together with our previous study which showed that GTC extract was more protective than butylated hydroxytoluene as an antioxidant, these results suggest that GTC as a mixture of EGCG, EGC, EC, and ECG may serve as an antioxidant in processed foods.     

Antioxidative activity of green tea catechin extract compared with that of rosemary extract

This study compared the antioxidative activity of green tea catechin (GTC) extract with that of rosemary extract in canola oil, pork lard, and chicken fat. The GTC extract was obtained from jasmine and longjing green teas and mainly consisted of four epicatechin isomers including (−)epigallocatechin gallate (EGCG), (−)epigallocatechin (EGC), (−)epicatechin (EC), and (−)epicatechin gallate (ECG). The oxidation was conducted at 100 ± 2°C by monitoring oxygen uptake. The oxygen consumption test demonstrated that GTC extract was much more effective than the rosemary extract against lipid oxidation in canola oil, pork lard, and chicken fat under the conditions of the present study. Together with our previous study which showed that GTC extract was more protective than butylated hydroxytoluene as an antioxidant, these results suggest that GTC as a mixture of EGCG, EGC, EC, and ECG may serve as an antioxidant in processed foods.     

Stabilization of seal blubber and menhaden oils with green tea catechins

Catechins, namely (−)epicatechin (EC), (−)epigallocatechin (EGC), (−)epicatechin gallate (ECG) and (−)epigallocatechin gallate (EGCG), were isolated from commercial Chinese green leaves. The antioxidant activity of isolated catechins was compared with those of α-tocopherol, butylated hydroxyanisole (BHA), butylated hydroxytolene (BHT) andtert-butylhydroquinone (TBHQ), all at 200 ppm, in refined, bleached and deodorized seal blubber oil and menhaden oil. The study was carried out under Schaal oven test conditions at 65°C over a 144-h period, except for weight gain measurements, which were continued for up to 200 h. Progression of oxidation was monitored by measuring changes in weight gain and values of peroxide, conjugated diene, and 2-thiobarbituric acid-reactive substances. Oils treated with tea catechins showed excellent oxidative stability as compared with samples that contained commonly used antioxidants, such as α-tocopherol, BHA, BHT, and TBHQ. The potency of catechins in prevention of oxidation of marine oils was in the decreasing order of ECG> EGCG> EGC> EC; ECG was slightly more effective than TBHQ in systems studied.     

Polyphenolic Profile and Antioxidant Activities of Oolong Tea Infusion under Various Steeping Conditions

The phenolic profile and antioxidant activities of oolong tea extract were investigated after tea was steeped in 90 or 100 °C water for 3 or 10 min. The extraction yield increased with increasing temperature and extended steeping time. However, higher temperature and longer time (100 °C water for 10 min) led to loss of phenolics. The aqueous extract of oolong tea (AEOT) at 100 °C for 3 min exhibited the strongest antioxidant activity. The major polyphenolic components of the AEOT were identified as (−)-epigallocatechin (EGC), (−)-epigallocatechin gallate (EGCG) and (−)-epicatechin-3-gallate (ECG). The two major catechins (EGC and EGCG) in the tea infusion contributed significantly to the investigated antioxidant activities [i.e., the 2,2-diphenyl-2-picrylhydrazyl hydrate (DPPH) radical scavenging and superoxide radical scavenging activities] with high correlation values in r = 0.9486 and 0.9327 for the EGC and r = 0.9592 and 0.8718 for the EGCG, respectively.     

GCG-Rich Tea Catechins are Effective in Lowering Cholesterol and Triglyceride Concentrations in Hyperlipidemic Rats

The (−)-gallocatechin gallate (GCG) concentration in some tea beverages can account for as much as 50% of the total catechins, as a result of sterilization. The present study aims to examine the effects of GCG-rich tea catechins on hyperlipidemic rats and the mechanisms associated with regulating cholesterol metabolism in the liver. By performing heat epimerization of (−)-epigallocatechin gallate (EGCG), we manufactured a mixture of catechins that had a GCG content of approximately 50% (w/w). In sucrose-rich diet-induced hyperlipidemic rats, the GCG-rich tea catechins exhibited strong activity in reducing plasma cholesterol and triglyceride concentrations. Furthermore, the hepatic cholesterol and triglyceride concentrations that had increased as a result of the sucrose-rich diet were reduced due to GCG-rich tea catechins consumption. In order to investigate the hyperlipidemic mechanism of GCG-rich tea catechins, we examined the hepatic expressions of LDL receptor and HMG-CoA reductase in hyperlipidemic rats. We further evaluated the action of purified GCG on LDL receptor activity, which is a key contributor to the regulation of cholesterol concentrations. We found that purified GCG increased LDL receptor protein level and activity to a greater extent than EGCG. In conclusion, our study indicates that GCG-rich tea catechins in tea beverages may be effective in preventing hyperlipidemia by lowering plasma and hepatic cholesterol concentrations.     

Binding of Natural and Synthetic Polyphenols to Human Dihydrofolate Reductase

Dihydrofolate reductase (DHFR) is the subject of intensive investigation since it appears to be the primary target enzyme for antifolate drugs. Fluorescence quenching experiments show that the ester bond-containing tea polyphenols (-)-epigallocatechin gallate (EGCG) and (-)-epicatechin gallate (ECG) are potent inhibitors of DHFR with dissociation constants (K_D)of 0.9 and 1.8 μM, respectively, while polyphenols lacking the ester bound gallate moiety [e.g., (-)-epigallocatechin (EGC) and (-)-epicatechin (EC)] did not bind to this enzyme. To avoid stability and bioavailability problems associated with tea catechins we synthesized a methylated derivative of ECG (3-O-(3,4,5-trimethoxybenzoyl)-(-)-epicatechin; TMECG), which effectively binds to DHFR (K_D = 2.1 μM). In alkaline solution, TMECG generates a stable quinone methide product that strongly binds to the enzyme with a K_D of 8.2 nM. Quercetin glucuronides also bind to DHFR but its effective binding was highly dependent of the sugar residue, with quercetin-3-xyloside being the stronger inhibitor of the enzyme with a K_D of 0.6 μM. The finding that natural polyphenols are good inhibitors of human DHFR could explain the epidemiological data on their prophylactic effects for certain forms of cancer and open a possibility for the use of natural and synthetic polyphenols in cancer chemotherapy.     

Constituents of Amomum tsao-ko and their radical scavenging and antioxidant activities

Constituents of the fruit of Amomum tsao-ko were investigated following a preliminary screening of the antioxidant activity of several extracts of the fruit of this plant that showed that the dichloromethane extract and the ethyl acetatesoluble and water-soluble fractions of the 70% aqueous acetone extract had higher activity than α-tocopherol and butylated hydroxytoluene (BHT). Eleven compounds were isolated from the ethyl acetate-soluble fraction, and their structures were elucidated as (+)-hannokinol (1), meso-hannokinol (2), (+)-epicatechin (3), (−)-catechin (4), β-sitosterol (5), β-sitosterol 3-O-glucoside (6), 2,6-dimethoxyphenol (7), protocatechualdehyde (8), protocatechuic acid (9), vanillic acid (10), and p-hydroxybenzoic acid (11) based on mass and various nuclear magnetic resonance (NMR) spectroscopic techniques. This is the first isolation of epicatechin and catechin from the genus Amomum. The radical scavenging activity of the isolated compounds was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and colorimetric and electron spin resonance (ESR) analyses. The antioxidant activity of the compounds was also determined based on the oxidative stability index (OSI). The catechins and catechol derivatives showed strong activities in both the DPPH radical scavenging activity and antioxidant activity assays.     

Preformed and Induced Chemical Resistance of Tea Leaf Against <Emphasis Type="Italic">Exobasidium vexans</Emphasis> Infection

Levels of (−)-epicatechin in tea cultivars resistant to blister blight leaf disease were significantly higher than those in susceptible cultivars, while the reverse was true for (−)-epigallocatechin gallate, suggesting that epicatechin was involved in the resistance mechanism. The content of the methylxanthines, caffeine and theobromine, in the leaf increased in the initial translucent stage of the disease, probably as a defense response to fungal attack. Epicatechin and epigallocatechin levels were less than in healthy tissues at this stage, but increases in the corresponding gallate esters suggested that they were being converted into esters. Although epicatechin and epigallocatechin levels decreased from translucent to mature blister stages, the decrease was not significant. The decrease in levels of epicatechin, epigallocatechin, and their esters on infection and the formation of cyanidin and delphinidin on oxidative depolymerization of the blisters suggests that proanthocyanidins may play a role in the defense mechanism. The high resistance of a purple green leafed cultivar is attributed to the additional catechin source provided by the high levels of anthocyanins present.     

Low erucic acid canola oil does not induce heart triglyceride accumulation in neonatal pigs fed formula

Canola oil is not approved for use in infant formula largely because of concerns over possible accumulation of triglyceride in heart as a result of the small amounts of erucic acid (22∶1n−9) in the oil. Therefore, the concentration and composition of heart triglyceride were determined in piglets fed from birth for 10 (n=4–6) or 18 (n=6) d with formula containing about 50% energy fat as 100% canola oil (0.5% 22∶1n−9) or 100% soybean oil, or 26% canola oil or soy oil (blend) with palm, high-oleic sunflower and coconut oil, providing amounts of 16∶0 and 18∶1 closer to milk, or a mix of soy, high-oleic sunflower and flaxseed oils with C₁₆ and C₁₈ fatty acids similar to canola oil but without 22∶1. Biochemical analysis found no differences in heart triglyceride concentrations among the groups at 10 or 18 d. Assessment of heart triglycerides using Oil Red O staining in select treatments confirmed no differences between 10-d-old piglets fed formula with 100% canola oil (n=4), 100% soy oil (n=4), or the soy oil blend (n=2). Levels of 22∶1n−9 in heart triglyceride and phospholipid, however, were higher (P<0.01) in piglets fed 100% canola oil or the canola oil blend, with higher levels found in triglycerides compared with phospholipids. The modest accumulation of 22∶1n−9 associated with feeding canola oil was not associated with biochemical evidence of heart triglyceride accumulation at 10 and 18 d.     

Restructing butterfat through blending and chemical interesterification. 1. Melting behavior and triacylglycerol modifications

Chemical interesterification of butterfat-canola oil blends, ranging from 100% butterfat to 100% canola oil in 10% increments, decreased solid fat content (SFC) of all blends in a nonlinear fashion in the temperature range of 5 to 40°C except for butterfat and the 90∶10 butterfat/canola oil blend, whose SFC increased between 20 and 40°C. The sharp melting associated with butterfat at 15–20°C disappeared upon interesterification. Heats of fusion for butterfat to the 60∶40 butterfat/canola oil blend decreased from 75 to 60 J/g. Blends with >50% canola oil displayed a much sharper drop in enthalpy. Heats of fusion were 30–50% lower on average for interesterified blends than for their noninteresterified counterparts. Both noninteresterified and interesterified blends deviated substantially from ideal solubility, with greater deviation as the proportion of canola oil increased. The change in the entropy of melting was consistently higher for noninteresterified blends than for interesterified blends. Chemical interesterification generated statistically significant differences for all triacylglycerol carbon species (C) from C₃₀ to C_56′ except for C_42′ and in SFC at most temperatures for all blends.     

Characterization of oil exhibiting high γ-linolenic acid from a genetically transformed canola strain

The seed oil from a genetically transformed canola (Brassica napus) containing 43% (w/w) of γ-linolenic acid (G, 18∶3n−6), 22% linoleic acid (L, 18∶2n−6), and 16% oleic acid (O, 18∶1n−9) was evaluated. In this high γ-linolenic acid canola oil (HGCO), the predominant 18∶3n−6-containing triacylglycerol (TG) molecular species were GGL (23%), GLO (20%), and GGG (11%). In the total TG, approximately 75% of the 18∶3n−6 was located at the sn-1,3 positions, while only 34% of linoleic acid was at the sn-1,3 positions. The GGL molecular species of HGCO contained approximately equal amounts of GLG and GGL positional isomers, while the GLO molecular species had 95% GOL and 5% GLO isomers. The general characteristics and the tocopherol and phytosterol contents were mostly similar between HGCO and nontransformed canola oil. No detectable amounts of amino acids and nucleotides were observed in the HGCO.     

Stoichiometric and kinetic studies on Ginkgo biloba extract and related antioxidants

Owing to increasing evidence showing the importance of lipid peroxidation in oxidative stress in vivo, the role and evaluation of antioxidants have received much attention. Ginkgo biloba extract (GBE), well-known as an efficient drug against diseases induced by free radicals, has been suggested to exert its effect by antioxidant action. A method was established to determine the activity of GBE as a hydrogen donor by stoichiometric and kinetic studies, and GBE was compared with several other antioxidants such as α-tocopherol, propyl gallate, and two kinds of flavonoids which are found in GBE, quercetin, and kaempferol. It was found that there were 6.62×10¹⁹ active hydrogens in 1g of GBE. Stoichiometric studies showed that one molecule of α-tocopherol reacted with one molecule of galvinoxyl radical. For quercetin, kaempferol and propyl gallate, the experimental stoichiometric numbers were 4.0, 1.9, and 3.1, respectively. The rates of reaction of antioxidants with galvinoxyl in ethanol were determined spectrophotometrically, using a stopped-flow technique. The second-order rate constant, k ₂, obtained at 25°C was 0.13 (g/l)⁻¹s⁻¹ for GBE and 5.9×10³, 2.1×10³, 1.2×10⁴, and 2.4×10³ M⁻¹s⁻¹ for quercetin, kaempferol, propyl gallate, and α-tocopherol, respectively. The second-order rate constant, k ₂′, on the molar basis of active hydroxyl groups in the tested substances obtained at 25°C decreased in the order of propyl gallate > α-tocopherol> quercetin>GBF∼kaempferol. This is the first study on GBE as an antioxidant which reports both stoichiometric and kinetic results.     

Characterization and oxidative stability of enzymatically produced fish and canola oil-based structured lipids

Two-kilogram quantities of structured lipids (SL) of menhaden fish and canola oils containing caprylic acids (8∶0) were produced in a laboratory-scale packed-bed bioreactor by acidolysis catalyzed by an immobilized lipase, Lipozyme IM, from Rhizomucor miehei. SL were characterized and their oxidative stabilities investigated. The SL contained 29.5% 8∶0 for fish oil and 40.15 for canola oil. Polyunsaturated fatty acids (PUFA) of fish oil remained unchanged after the modification while PUFA of canola oil were reduced from 29.6 to 21.2%. Monoenes, especially 18∶1n−9, were completely replaced by 8∶0 in fish oil and reduced from 61.9 to 34.7% in canola oil. Downstream processing of enzymatically produced SL led to loss in natural total tocopherol contents of the fish and canola oils. The effects of antioxidants such as α-tocopherol (TOC), tert-butylhydroxyquinone (TBHQ), and combinations thereof on the oxidative stability of SL were investigated. SL were analyzed for oxidative stability index, peroxide value, conjugated diene content, free fatty acid content, iodine value, saponification number, and thiobarbituric acid value. Iodine value of unmodified fish oil (154.71) was reduced to 144.10 and that of canola oil (114.49) to 97.27 after modification. The SN increased from 183.72 to 242.63 for fish oil and from 172.50 to 227.90 for canola oil. TBHQ exhibited better antioxidant effects than TOC. A combination of TBHQ/TOC also proved to be an effective antioxidant for SL. We suggest the addition of antioxidants to enzymatically produced and purified SL.     

Accumulation of eicosapentaenoic acid in plasma phospholipids of subjects fed canola oil

The metabolism of α-linolenic acid from canola oil was studied in eight normolipidemic men. The 42-day study was divided into three periods: a 6-day pre-experimental and two 18-day experimental. Approximately 75% of the dietary fat (28% of total energy) was provided by a mixture of fats during the pre-experimental period and either canola oil (CO) or sunflower oil (SO) during the experimental periods. The CO and SO diets were fed in a cross-over design. The ratios of linoleic to linolenic acid were 2.6∶1 and 73.9∶1 in the CO and SO diets, respectively. Dietary fat source had an effect on plasma phospholipid fatty acids: 18∶1n−9, 18∶3n−3 and 20∶5n−3 were higher (p<0.05), and 18∶2n−6 was lower in the phosphatidylcholine fraction; 18∶1n−9 was higher and 20∶4n−6 lower in the phosphatidyl-ethanolamine fraction; and 18∶1n−9 and 20∶5n−3 were higher and 20∶4n−6 and 22∶6n−3 were lower in the alkenylacyl-ethanolamine phospholipid fraction on the CO diet as compared to the SO diet. Consumption of the canola oil diet resulted in higher n−3 fatty acid levels and lower n−6 fatty acid levels in plasma phospholipids than consumption of the sunflower oil diet.     

The effect of supercooling on crystallization of cocoa butter-vegetable oil blends

The solid fat content (SFC), Avrami index (n), crystallization rate (z), fractal dimension (D), and the pre-exponential term [log(γ)] were determined in blends of cocoa butter (CB) with canola oil or soybean oil crystallized at temperatures (T _Cr) between 9.5 and 13.5°C. The relationship of these parameters with the elasticity (G′) and yield stress (σ^*) values of the crystallized blends was investigated, considering the equilibrium melting temperature (T _M ^o) and the supercooling (i.e., T _Cr ^o−T _M ^o) present in the blends. In general, supercooling was higher in the CB/soybean oil blend [T _M ^o=65.8°C (±3.0°C)] than in the CB/canola oil blend [T _M ^o=33.7°C (±4.9°C)]. Therefore, under similar T _Cr values, higher SFC and z values (P<0.05) were obtained with the CB/soybean oil blend. However, independent of T _Cr TAG followed a spherulitic crystal growth mechanism in both blends. Supercooling calculated with melting temperatures from DSC thermograms explained the SFC and z behavior just within each blend. However, supercooling calculated with T _M ^o explained both the SFC and z behavior within each blend and between the blends. Thus, independent of the blend used, SFC described the behavior of G′_eq and σ^* and pointed out the presence of two supercooling regions. In the lower supercooling region, G′_eq and σ^* decreased as SFC increased between 20 and 23%. In this region, the crystal network structures were formed by a mixture of small β′ crystals and large β crystals. In contrast, in the higher supercooling region (24 to 27% SFC), G′_eq and σ^* had a direct relationship with SFC, and the crystal network structure was formed mainly by small β′ crystals. However, we could not find a particular relationship that described the overall behavior of G′_eq and σ^* as a function of D and independent of the system investigated.     

Dietary manipulation of long-chain polyunsaturated fatty acids in the retina and brain of guinea pigs

High levels of n−6 docosapentaenoic acid (22∶5n−6) have been reported in the retina of guinea pigs fed commercially-prepared grain-based rations (commercial diet). In rats and monkeys, high levels of 22∶5n−6 are an indicator of n−3 polyunsaturated fatty acid (PUFA) deficiency. We have examined the fatty acid composition of the retina and brain in guinea pigs fed a commercial diet or one of three semi-purified diets containing three different levels of n−3 PUFA. The diets comprised a diet deficient in n−3 PUFA (semi-purified diet containing safflower oil), two diets containing α-linolenic acid (standard commercial laboratory diet and semi-purified diet containing canola oil), and a diet containing α-linolenic acid, eicosapentaenoic acid, and docosahexaenoic acid (DHA) (semi-purified diet containing canola oil, safflower oil, and fish oil). Two groups of guinea pigs were given the diets from day 1 to 4 wk or day 1 to 8 wk, when they were sacrificed and the retinal tissues were extracted and analyzed for PUFA content by gas-liquid chromatography. Fatty acid analyses of the retinal phospholipids of the four-week-old animals revealed that the group fed DHA (from the fish oil) had the highest level of DHA (32%), compared with values of 19 and 13% for the groups fed canola oil diet and commercial diet, respectively, and 2% for the group fed the diet deficient in n−3 PUFA. The levels of 22∶5n−6 in the retinal lipids were inversely related to the DHA values, being 0.6, 6.6, 11.4, and 20.6 for the fish oil, canola oil, commercial diet, and safflower oil diet groups, respectively. The long-chain PUFA profiles in the brain phospholipids of the four-week-old group were similar to those from the retina. The retinal PUFA values for the eight-week-old animals were similar to the four-week-old group. The safflower oil diet induced a greater deficit of DHA in retinal lipids than has been reported in rats and monkeys fed similar diets. The guinea pigs fed the commercial diet had retinal and brain PUFA patterns similar to that produced by n−3 PUFA-deficient diets in rats and monkeys. Guinea pigs fed the canola oil diet had significantly greater retinal DHA levels than those fed the commercial diet, but lower than those fed fish oil. The data suggest that the guinea pig has a reduced capacity for DHA synthesis from α-linolenic acid as compared with other mammals. Supplementation of guinea pig diets with fish oil produced high retinal and brain DHA levels and prevented the accumulation of 22∶5n−6.     

Copper and Iron Determination with [<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-Bis(salicylidene)-2,2′-dimethyl-1,3-propanediaminato] in Edible Oils Without Digestion

A new method for the determination of copper(II) and iron(III) in liquid edible oils which does not require a digestion step was developed. The suggested method involves extraction of metals with [N,N′-bis(salicylidene)-2,2′-dimethyl-1,3-propanediaminato] (LDM) followed by flame atomic absorption spectrometry measurement. As a first step, metal complexes of copper(II) and iron(III) ions with LDM were investigated spectrophotometrically. After the analytical properties and experimental conditions of the complexation had been determined, these findings were used to determine the extraction period as a second step. Experimental conditions were optimized using a central composite design. Optimum conditions for Cu(II) and Fe(III) extractions from oil were found: the ratios of the volume of Schiff base solution used to the mass of oil (V _LDM/m _oil; mL g⁻¹) were 0.76 and 1.19 mL g⁻¹, the stirring times were 73 and 67 min, and the temperatures were 31 and 28 °C, respectively. The developed extraction and determination method was tested on certified reference materials; the recovery percentages were found to be 99.4 ± 2.8 and 100.2 ± 5.6 for Cu(II) and Fe(III), respectively. The suggested method was performed on real samples such as olive oil, sunflower oil, corn oil, canola oil and recovery values between 97.2–102.1 for Cu(II) and 94.5–98.6 for Fe(III) were determined. It was concluded that the developed method has some advantages over the common traditional method including rapidity, sensitivity, accuracy, reduced risk and cost.     

Paradoxical effect of n−3-containing vegetable oils on long-chain n−3 fatty acids in rat heart

Flaxseed, echium, and canola oils contain α-linolenic acid (18∶3n−3, ALA) in a range of concentrations. To examine their effect on elevating cardiac levels of long-chain n−3 FA, diets based on these n−3-containing vegetable oils were fed to rats for 4 wk. Sunflower oil, which contains little ALA, was a comparator. Despite canola oil having the lowest ALA content of the three n−3-containing vegetable oils, it was the most potent for elevating DHA (22∶6n−3) levels in rat hearts and plasma. However, the relative potencies of the dietary oils for elevation of EPA (20∶5n−3) in heart and plasma followed the same rank order as their ALA content, i.e., flaxseed>echium>canola>sunflower oil. This paradox may be explained by lower ALA intake leading to decreased competition for Δ6 desaturase activity between ALA and the 24∶5n−3 FA precursor to DHA formation.     

Homogeneous catalytic hydrogenation of canola oil using a ruthenium catalyst

Dichlorodicarbonylbis (triphenylphosphine) ruthenium (II), RuCl₂ (CO)₂ (PPh₃)₂, was investigated as a catalyst for edible oil hydrogenation in a preliminary screening of potential catalysts for producing partially hydrogenated fats with lowtrans-isomer content. Refined, bleached and deodorized canola oil was hydrogenated using 1.77 × 10⁻⁵ − 6.64 × 10⁻⁴ mol/kg-oil of ruthenium catalyst equivalent to 1.79 × 10⁻⁴ − 6.71 × 10⁻³ wt% Ru. The effects of temperature (50–180 C) and pressure (50–750 psig) on reaction rate,trans-isomer content and fatty acid composition were examined. The activities of RuCl₂ (CO)₂ (PPh₃)₂ and nickel (Nysel HK-4 and AOCS standard nickel catalyst) were compared on a molar basis. At 4.40 × 10⁻⁴ mol/kg-oil (0.0026 wt/Ni or 0.0044 wt% Ru), 140 C and 50 psig, the nickel catalysts were completely inactive, but the ruthenium catalyst produced an IV drop of 40 units in 60 min. At 110 C, 750 psig and 1.34 × 10⁻⁴ mol/kg-oil (1.35 × 10⁻³ wt% Ru), a hydrogenation rate of 0.89 ΔIV/min and a maximumtrans-isomer content of 10.4% (IV=45.0) was obtained with the ruthenium catalyst.     

Radical scavenging activity of canola hull phenolics

Possible use of canola hulls as a source of natural anti-oxidants was explored. Cyclone canola hulls were extracted with methanol (30 to 80%, vol/vol) and acetone (30 to 80%, vol/vol). The free radical-scavenging activity of phenolic extracts so prepared was evaluated using the 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) radical ion (ABTS^o−), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, and chemiluminescence assays. The total content of phenolics in prepared extracts from canola hulls ranged from 15 to 136 mg sinapic acid equivalents per gram of extract. Higher levels of condensed tannins were detected in the acetone extracts than in the corresponding methanolic counterparts. Seventy and 80% (vol/vol) acetone extracts displayed markedly stronger antioxidant activity than any of the other extracts investigated. Statistically significant linear correlations were found between TEAC (Trolox equivalent antioxidant capacity) values (expressed in mM of Trolox equivalents per gram of extract) and total pehnolics, TEAC and total condensed tannins (i.e., determined using the modified vanillin and pronthocyanidin assays), as well as TEAC and protein precipitation activity of phenolic extracts (i.e., measured using the dye-labeled assay). The antioxidant activities of extracts as determined by the ABTS^o− radical ion assay correlated highly with those of the chemiluminescence and DPPH radical assays.