Potential of commonly consumed green leafy vegetables for their antioxidant capacity and its linkage with the micronutrient profile

Green leafy vegetables (GLV) offer a cheap but rich source of a number of micronutrients and other phytochemicals having antioxidant properties. The potential of 30 GLV in the raw and cooked form as natural antioxidant supplements for vegetarian diets was assessed. There was a large variability in the values of antioxidant activity of various GLV extracts in the lipid micelles (1.5–5.6 mM vitamin E/100 g for raw samples and 1.6–3.8 mM vitamin E/100 g for cooked samples). Similar to thiobarbituric acid reactive substances values, the super oxide scavenging ability values also exibited large variation (10.6–55.9), with significantly higher values in the raw state than the cooked state (P<0.001). Omum leaves, radish leaves and lettuce had high values for this index. The range of values for ferrous iron chelating activity was from 9.3 to 65.7 mM EDTA/100 g food material, indicating again a large variability in this assay. Leaves of coriander, amaranthus viridis, colcasia green and drumstick showed high values, while Amaranthus p. Colocasia black and amaranthus red exibited low values. Differences between raw and cooked values were highly significant for all the three indices (P<0.001).     

Potential of Traditionally Cooked Green Leafy Vegetables as Natural Sources for Supplementation of Eight Micronutrients in Vegetarian Diets

The potential of 24 green leafy vegetables (GLV) in cooked form was assessed for the contents of eight micronutrients; bioavailability of iron, zinc and copper; and for proximate principles. The bioavailable densities of iron, zinc and copper (1.3±1.2, 1.1±0.5, 0.7±0.3 mg/1000 kcal) in individual GLV and GLV-based meals were higher than those in meals based on cereals or legumes. Average bioavailable iron density in particular, was 3.6 times higher (P<0.01) than the average value for composite cereal–legume-based meals indicating GLV as promising fortificants of iron for vegetarians. Contents per 100 g cooked weight of beta-carotene (80–5920 μg), ascorbic acid (2.2–58.2 mg), folic acid (35.6–185 μg), riboflavin (0.03–0.08 mg) and thiamin (0.04–0.46 mg) were found to show large variability among different GLV but the average levels of beta-carotene and ascorbic acid were significantly higher than the other food classes (P<0.05). The contents of the vitamins were compared in cereal–legume meals (12), cereal–fruit vegetable meals (16), and cereal–GLV meals (30) in another experiment. The results indicate a highly significant and 8.7-13.1-fold rise in beta-carotene levels, and a 1.7–2.3-fold rise in the levels of folic acid and riboflavin in GLV meals as compared to other meals indicating the potential for increasing these three vitamin levels using GLV.     

GLV supplements increased plasma β–carotene, vitamin C, zinc and hemoglobin in young healthy adults

Summary Background Green leafy vegetables (GLV) are rich sources of β–carotene, iron and other micronutrients. Our in vitro studies have demonstrated good antioxidant potential in GLV. Moreover linkages of GLV intakes with plasma retinol and ascorbic acid were seen in apparently healthy Indians. Aim of the study To investigate the effect of GLV as a natural fortificant of multiple micronutrients through a prospective human trial. Methods Short–term (0–4 h) response (AUC) of single dose of 7.9 mg β–carotene and 130 mg ascorbic acid through a spinach–carrot meal against the standard meal without GLV plus10 mg β–carotene and 150 mg ascorbic acid tablets was studied in two groups of 4 young volunteers each. In the second trial of 3 weeks' supplementation, 5 groups of young adults (n = 40) were given either 100 g GLV/day alone or with tablets of vitamin E (100 mg/day), or C (100 mg/day) or more oil (5 g/day) or non–GLV meal with tablet of β–carotene (10 mg/day). Hemoglobin (Hb), plasma β–carotene, zinc, vitamin C, glucose, and triglycerides were measured. Results In a postprandial response, AUC were comparable in both GLV and standard meals for β–carotene and ascorbic acid. In case of triglycerides and glucose AUC the GLV meal showed a better recovery to the baseline value after 4 hours than the standard meal. Three weeks' supplementation of GLV with more oil resulted in significant increase of plasma β–carotene (51%) and Hb (9%). GLV with vitamin E showed a significant increase in plasma β–carotene (40%), Hb (8%) and plasma vitamin C (6%). Supplementing β–carotene without GLV significantly increased Hb (11%), plasma zinc (14%) in addition to β–carotene. Multiple regression analyses weighted for energy intake indicated a significant association of percent increase in Hb with intakes of iron, riboflavin, folic acid, β–carotene, copper, phytate and fiber (p < 0.01), percent change in plasma zinc with intakes of zinc, β–carotene, vitamin C, riboflavin, copper, iron, and thiamin (p < 0.01), percent change in vitamin C with intakes of vitamin C, vitamin E, niacin, riboflavin, thiamin, β–carotene, zinc, phytate and fiber (p < 0.05) and percent change in plasma β–carotene with intakes of β–carotene, thiamin, folic acid, zinc, phytate and tannins (p < 0.05). Conclusion Using 100 g GLV/day with 10 g oil could be a single moderate strategy for supplementation of iron, β–carotene, ascorbic acid and zinc.     

The nutrient content of five traditional South African dark green leafy vegetables—A preliminary study

The nutrient content (proximate composition, vitamin B₂, ß-carotene, iron, zinc, magnesium, calcium and phosphorus) of 5 traditional dark green leafy vegetables, traditionally consumed by rural inhabitants of South Africa (SA), was determined in this study. The nutritional dilemma in SA, with many children and adults suffering from micronutrient deficiencies, is a strong motivation for determining the nutritional composition of traditional foods. The moisture, protein, ash and fat content in the raw leaves per 100 g ranged from 81.0 to 89.9 g/100 g, 3.49 to 5.68 g/100 g, 1.42 to 3.23 g/100 g and 0.12 to 0.36 g/100 g respectively. There was an increase in moisture content in the cooked leaves, while the protein, fat and ash decreased during the cooking process. Raw misbredie (Amaranthus tricolor), pumpkin leaves (Curcubita maxima) and cat's whiskers (Cleome gynandra) had a high iron content compared to cowpea leaves (Vigna unguiculata) and wild jute (Corchorus olitorius), which in nutritional terms might play a role in combating iron deficiency in SA. The zinc content ranged from 0.5 to 1.0 mg/100 g, while the magnesium ranged from 54.7 mg to 146 mg/100 g. As expected, the minerals decreased during cooking. Cowpea leaves was the poorest source of minerals compared to the other leafy vegetables but had a good index of nutritional quality for protein. Raw and cooked pumpkin leaves had the highest index of nutritional quality for protein. Both raw and cooked leafy vegetables contained high levels of beta-carotene (with total beta-carotene levels in the range of 796–6134 μg/100 g) but low levels of vitamin B₂ (0.01–0.12 mg/100 g).     

Quantification of Phytochemicals,Cellular Antioxidant Activities and Antiproliferative Activities of Raw and Roasted American Pistachios (Pistacia vera L.)

The consumption of pistachios has been linked to many potential health benefits. Phytochemicals in pistachios, including phenolics, vitamin E and carotenoids, have been considered to make contributions to the health benefits. The objectives of this study were (1) to explore the phytochemical profiles (total phenolics and total flavonoids, including both free and bound forms), selected phytochemicals, vitamin E and carotenoids of raw and roasted pistachios; (2) to determine total antioxidant activity and cellular antioxidant activity (CAA); and (3) to explore antiproliferative activities of pistachio extracts against human breast, liver and colon cancer cells in vitro. Both raw and roasted pistachios contained high total phenolics, at 479.9 ± 10.2 (raw) and 447.9 ± 9.4 (roasted) mg GAE/100 g, respectively, and high flavonoids, at 178.4 ± 10.6 (raw) and 144.1 ± 7.4 (roasted) mg GAE/100 g, respectively. The contributions of the free form to the total phenolics in pistachios were 82% (raw) and 84% (roasted), respectively, and the contributions of the free form to the total flavonoids in pistachios were 65% (raw) and 70% (roasted), respectively. Gentisic acid and catechin were the major phenolics in raw and roasted pistachios, respectively. Both raw and roasted pistachios had similar total antioxidant activity evaluated by Oxygen-Radical-Scavenging Capacity (ORAC) assay, at 7387.9 ± 467 (raw) and 7375.3 ± 602 (roasted) μmol TE/100 g, respectively. Both raw and roasted pistachio extracts exhibited cellular antioxidant activity inhibiting peroxyradical radical-induced oxidation, with CAA values of 77.39 ± 4.25 (wash) and 253.71 ± 19.18 (no wash) μmol QE/100 g of raw pistachios and 115.62 ± 3.02 (wash) and 216.76 ± 6.6 (no wash) μmol QE/100 g of roasted pistachios. Roasted pistachios contained more vitamin E when compared with raw pistachios, while raw pistachios contained more carotenoids than the roasted pistachios. Additionally, the free form of roasted pistachios extracts exhibited superior antiproliferation activity against HepG2, Caco-2 and MDA-MB-231 cancer cells in a dose-dependent manner, with EC₅₀ 34.73 ± 1.64, 36.66 ± 3.3 and 7.41 ± 0.82 mg per mL, respectively. These results provided new knowledge about the phytochemical profiles, antioxidant activity, cellular antioxidant activity and antiproliferative activity of raw and roasted pistachios.     

Antioxidant properties of raw and processed cabbages

To study the effect of polyphenolics on antioxidant activities of cabbages, the amounts of total phenolics, total flavonoids, antioxidant capacity and individual phenolic compounds in raw and processed cabbages were determined. Fresh and pickled red cabbages exhibited the highest total phenolic contents (393.1+/-10.8 mg and 366.3+/-3.6 mg gallic acid equivalents/100 g fresh sample, respectively). Fresh and pickled red cabbages were also highest in flavonoids (108.1+/-9.3 mg and 72.4+/-4.4 mg catechin equivalents/100 g fresh sample, respectively). The antioxidant capacity (expressed as vitamin C equivalent antioxidant capacity) ranged from 57.1 to 695.6 mg vitamin C equivalents/100 g fresh sample, where raw and pickled red cabbages exhibited the highest antioxidant capacity. There was a good linear relationship between the total phenolics and antioxidant capacity (r2=0.9743), and between the total flavonoids and antioxidant capacity (r2=0.9557); however, the relationship between the ascorbic acid content and antioxidant capacity was very low (r2=0.1442). The antioxidant capacity of raw and processed cabbages was highly correlated with their contents of polyphenolics. Kaempferol, quercetin, and apigenin were the major flavonoids existing in cabbages except for raw and pickled red cabbages, where cyanidin was the predominant flavonoid (73.6-117.7 mg/kg). In the red cabbages, cyanidin was the major contributor to the antioxidant capacity as well as the content of total phenolics and flavonoids.     

Vitamin C levels in fresh, frozen and canned broad beans in relation to their varieties and degree of maturity

The content of vitamin C was investigated in seeds of broad been, the cultivars Windsor Bia?y, Comprimo RS, Green Hangdown, and Threefoldwhite, harvested, frozen or canned with the content of dry matter at the level of 30%. Moreover, in cultivars Comprimo RS and Threefoldwhite the vitamin C was determined as depending on seed maturity within 25-40% of dry matter at 5% intervals. The compared broad bean cultivars, frozen or canned at the level of 30% d.w. in seeds differed by the vitamin C content. The extreme differences reached 21% for the raw material, 32% for frozen seeds cooked, and 15% for canned appertized seeds. However, the ranking of cultivars in the final products differed from that in the raw material. The vitamin C content decreased with increasing degrees of seed ripeness in the range from 25-40%. This particularly concerns fresh seeds of Threefoldwhite cv. In the final products differences were smaller and reached 2-6% in cooked frozen seeds and 18-24% in appertized canned seeds. Blanching decreased the vitamin C content by 14-43%. Freezing of blanched seeds and the 6-month storage of frozen goods decreased this content by about 24-56%. Frozen whole seeds contained 9.3-13.8 mg of vitamin C in 100 g after cooking (compared with fresh seeds, the losses reached 56-73%) and appertized canned seeds 8.2-11.7 mg in 100 g (compared with fresh seeds, the losses reached 63-73%). The average difference in favour of cooked frozen seeds reached 17%. The difference in vitamin C content between whole seeds and cotyledones varied within 1-9%.     

Extent of error in estimating nutrient intakes from food tables versus laboratory estimates of cooked foods

Individual cooked foods (104) and composite meals (92) were examined for agreement between nutritive value estimated by indirect analysis (E) (Indian National database of nutrient composition of raw foods, adjusted for observed moisture contents of cooked recipes), and by chemical analysis in our laboratory (M). The extent of error incurred in using food table values with moisture correction for estimating macro as well as micronutrients at food level and daily intake level was quantified. Food samples were analyzed for contents of iron, zinc, copper, beta-carotene, riboflavin, thiamine, ascorbic acid, folic acid and also for macronutrients, phytate and dietary fiber. Mean percent difference in energy content between E and M was 3.07+/-0.6%, that for protein was 5.3+/-2.0%, for fat was 2.6+/-1.8% and for carbohydrates was 5.1+/-0.9%. Mean percent difference in vitamin contents between E and M ranged from 32 (vitamin C) to 45.5% (beta-carotene content); and that for minerals between 5.6 (copper) to 19.8% (zinc). Percent E/M were computed for daily nutrient intakes of 264 apparently healthy adults. These were observed to be 108, 112, 127 and 97 for energy, protein, fat and carbohydrates respectively. Percent E/M for their intakes of copper (102) and beta-carotene (114) were closer to 100 but these were very high in the case of zinc (186), iron (202), and vitamins C (170), thiamine (190), riboflavin (181) and folic acid (165). Estimates based on food composition table values with moisture correction show macronutrients for cooked foods to be within +/- 5% whereas at daily intake levels the error increased up to 27%. The lack of good agreement in the case of several micronutrients indicated that the use of Indian food tables for micronutrient intakes would be inappropriate.     

Vitamin D3 and 25-hydroxyvitamin D3 in raw and cooked pork cuts

The contents of vitamin D₃ and its metabolically active metabolite 25-hydroxyvitamin D₃ (25OHD₃) were examined by HPLC in different parts of four common raw pork cuts (loin boneless, leg inside, thin belly, neck) and in cooked meat (loin boneless). In whole raw pork cuts, varying in fat content from 2.2 to 26.5 g/100 g, concentrations of vitamin D₃ from 0.05 to 0.21 μg/100 g were measured. Pork cuts also contained significant amounts of 25OHD₃, from 0.07 to 0.14 μg/100 g. Further, the study demonstrated that most of the vitamin D₃ and 25OHD₃ is located in the fatty tissues, and that rind, despite its limited fat content, has a high concentration of vitamin D₃ and 25OHD₃. Cooking increased vitamin D₃ and 25OHD₃ calculated per 100 g of tissue in all parts and in the whole cut (in whole cuts in raw and cooked meat, respectively: vitamin D₃: 0.15 (0.08–0.24) μg/100 g and 0.18 (0.11–0.28) μg/100 g; P=0.33; 25OHD₃: 0.09 (0.06–0.18) μg/100 g and 0.13 (0.10–0.18) μg/100 g; P=0.02); however, correcting for differences in dry matter content, ameliorated all significant differences. 25OHD₃ has a higher (from 1.5 to 5 times) biological activity than vitamin D₃. Meat 25OHD₃ contributes significantly to vitamin D activity. Food databases should include concentrations of both vitamin D and 25OHD.     

Oral vitamin B12 supplementation reduces plasma total homocysteine concentration in women in India

People in India have a high prevalence of low vitamin B12 status and high plasma total homocysteine (tHcy) concentrations. In a proof of principle trial, we studied the effect of oral vitamin B12 (500 microg) and/or 100 g cooked green leafy vegetables (GLV) every alternate day in a 2x2 factorial design over a 6-week period. Forty-two non-pregnant vegetarian women (age 20-50 years) were randomly allocated to four study groups. Clinical measurements were made at the beginning and at the end of the study, and blood samples were collected before, and 2 and 6 weeks after commencement of intervention. Forty women completed the trial. Twenty-six women had low vitamin B12 status (<150 pmol/L) and 24 had hyperhomocysteinemia (>15 micromol/L). GLV supplementation did not alter plasma folate or tHcy. Vitamin B12 supplementation increased plasma vitamin B12 concentration (125 to 215 pmol/L, p <0.05) and reduced tHcy concentration (18.0 to 13.0 micromol/L, p <0.05) within first 2 weeks, both of which remained stable for the next 4 weeks. Plasma vitamin B12 and tHcy concentrations did not change in those who did not receive vitamin B12, and there was no change in plasma folate concentration in any of the groups. Blood haemoglobin concentration increased marginally within first two weeks in those women who received vitamin B12 (by 3 g/L, p <0.05) and the number of women with macrocytosis decreased from 2 to zero. There was no change in vibration sensory threshold during the period of the study. High-dose per oral vitamin B12 supplementation significantly reduced plasma tHcy within 2 weeks but did not achieve normal plasma tHcy concentration even after 6 weeks. People in India have a high prevalence of low vitamin B12 status and high plasma total homocysteine (tHcy) concentrations.     

Antioxidant and micronutrient potential of common fruits available in the Indian subcontinent

Considering the scanty information on Indian fruits, 36 commonly consumed fruits were assessed for inhibition of thiobarbituric acid reactive substances, superoxide scavenging activity and ferrous ion-chelating ability along with levels of micronutrients (namely ascorbic acid, beta-carotene, riboflavin, thiamine, zinc, copper, iron, manganese, selenium and total polyphenols). Fruits exhibited 24-173% variability for the 13 study parameters. Fresh fruits exhibited 3.5-4 times higher antioxidant capacity than dry fruits. Ascorbic acid was highest in gooseberry (445 mg/100 g), and beta-carotene was highest in ripe mango 1,200 mg/100 g. Selenium levels could supply 0-33% of the recommended dietary allowance. There was a strong association between different indices of antioxidant capacity (P<0.001), thiobarbituric acid reactive substances with selenium levels (P<0.01), and superoxide scavenging activity and ferrous ion-chelating ability with zinc content (P<0.05). Results emphasize need for the antioxidant quality of fruit in addition to the quantity of fruit consumption.     

β-Carotene and mineral content of different Chenopodium species and the effect of cooking on micronutrient retention

In the present study, the β-carotene, calcium, iron and zinc content in the leaves of 46 accessions of three Chenopodium species viz. Chenopodium album, C. album ssp. amaranticolor and Chenopodium quinoa was investigated. A wide range of variability, inter-specific as well as varietal, for the β-carotene [0.19-5.91 mg 100 g(- 1) fresh weight (FW)], calcium (358.35-960.10 mg 100 g(- 1) FW), iron (0.56-7.90 mg 100 g(- 1) FW) and zinc content (0.07-4.26 mg 100 g(- 1) FW) was observed. The C. album ssp. amaranticolor accessions IC341710 and IC469275 had a high content of all the four nutrients and were ideal food to alleviate nutritional deficiencies in humans. Nutritionally rich IC341710 and IC469275 were further studied to estimate micronutrient retention in cooked leaves. Between the two methods used to cook leaves, stir-frying showed better retention of micronutrients than pressure cooking.     

Antioxidant, hepatoprotective, and ameliorative effects of methanolic extract of leaves of Grewia mollis Juss. on carbon tetrachloride-treated albino rats

The methanolic extract of Grewia mollis leaves was evaluated in vivo for its antioxidant and hepatoprotective properties. Oxidative stress was induced in rats by administering carbon tetrachloride (CCl(4)) intraperitoneally at a dose of 0.6 mL/kg, whereas the crude plant extract and standard antioxidant (vitamin E) were administered at a dose of 5 mg/kg and 50 mg/kg, respectively. The effect of G. mollis crude extracts and vitamin E on malondialdehyde (MDA) and liver function parameters such as protein, bilirubin, aspartate aminotransferase, and alanine aminotransferase were measured spectrophotometrically. The methanolic extract of G. mollis leaves and vitamin E showed a significant (P<.05) hepatoprotective potential by lowering the serum levels of bilirubin, aspartate aminotransferase, and alanine aminotransferase and decreasing MDA levels in rats pretreated or post-treated with CCl(4). Based on these results, it is concluded that G. mollis leaves contain potent antioxidant compounds that could offer protection against hepatotoxicity as well as ameliorate preexisting liver damage and oxidative stress conditions.     

The effect of soaking and cooking on the oxalate content of taro leaves

Pacific Island people commonly eat taro (Colocasia esculenta var. Schott) as a staple food in their home islands and also like to consume this familiar food when living in New Zealand. Some of these foods are imported from the islands and some attempts are, currently, being made to grow these crops in New Zealand. The taro leaves in this experiment were grown in a greenhouse in the North Island of New Zealand. The soluble oxalate content of the raw leaves was 236.10 mg oxalate/100 g wet matter (WM). Soaking the raw leaves in water for 30 min marginally reduces the soluble oxalate content by leaching into the tap water. Soaking for 18 h results in a 26% reduction in the soluble oxalate content of the raw leaves. During the soaking treatments the insoluble oxalate (calcium oxalate) content of the leaves remained constant (mean 171.64 mg oxalate/100 g WM).Boiling the taro leaves resulted in a 36% loss of soluble oxalates, while the soluble oxalate content of baked tissue was very similar to the raw tissue. The mean insoluble oxalate content of the raw, boiled and baked tissue was 226.28 mg oxalate/100 g WM. Overall, boiling the taro leaves was an effective way of reducing the soluble oxalate content of the cooked tissue.     

Antioxidative mechanisms of whole-apple antioxidants employing different varieties from Luxembourg

Many health beneficial functions of dietary ingredients, including antimutagenity and anticarcinogenity, have been discussed in relation to their antioxidant properties. In this study, antioxidative mechanisms of whole-apple antioxidants (from seven varieties) were investigated using the 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging capacity assay, the ferric-reducing antioxidant power (FRAP) assay, and the ferrous iron(II) chelating activity assay. Results indicated the ability of primary antioxidants to act as hydrogen or electron donors, with considerable differences depending on variety, with ABTS and FRAP values ranging from 270 to 1,142 mg of vitamin C equivalents/100 g and from 695 to 3,143 μmol of Fe/100 g, respectively. However, varieties did not display measurable chelating activity except for Florina and Graham, exhibiting a weak activity (0.1-0.2 μg of EDTA equivalents/100 g). Correlation analyses showed that polyphenols were major primary antioxidants contributing to antioxidative mechanisms (r>0.99, P<.001), whereas their involvement as secondary antioxidants (i.e., as chelating compounds) was negligible. Our findings further showed that the intake of 100 g of apple fruits can provide antioxidants equivalent to approximately 270-1,140 mg of vitamin C, with highest antioxidant concentrations for the older varieties Grauapfel and Goldparm?ne.     

Vitamin C in Inuit Traditional Food and Women's Diets

Vitamin C values for 37 traditional foods (TFs) of the Inuit of the Canadian Arctic and women's intakes from TF and market food (MF) are reported. This is the first report on vitamin C values in several traditional food samples. There are a variety of rich sources of vitamin C from animal and plant food with the most notable among items with multiple samples being raw fish (Coregonus spp.) eggs (49.6±12.3 mg/100 g, mean± S.D.), raw whale (Delphinapterus leucas and Monodon monoceros) skin, locally termed “mattak”, (36.0±8.7 and 31.5±7.0 mg/10 g), caribou liver (Rangifer tarandus) (23.8±4.9 mg/100 g), ringed seal liver (Phoca hispida) (23.8±3.8 mg/100 g), and blueberries (Vaccinium uliginosum) (26.2±4.9 mg/100 g). Dietary analysis of 20–40-year-old women's 24-h recalls for vitamin C as TF and MF revealed total mean intake of 60±8 mg/day (mean± S.E.). TF contributed only 20% of total intake, although there was significant seasonal variation (P<0.02). While rich sources of vitamin C are present as TF, the primary contemporary dietary sources of this nutrient are fortified MF.     

The effect of soaking and cooking on the oxalate content of taro leaves

Pacific Island people commonly eat taro (Colocasia esculenta var. Schott) as a staple food in their home islands and also like to consume this familiar food when living in New Zealand. Some of these foods are imported from the islands and some attempts are, currently, being made to grow these crops in New Zealand. The taro leaves in this experiment were grown in a greenhouse in the North Island of New Zealand. The soluble oxalate content of the raw leaves was 236.10 mg oxalate/100 g wet matter (WM). Soaking the raw leaves in water for 30 min marginally reduces the soluble oxalate content by leaching into the tap water. Soaking for 18 h results in a 26% reduction in the soluble oxalate content of the raw leaves. During the soaking treatments the insoluble oxalate (calcium oxalate) content of the leaves remained constant (mean 171.64 mg oxalate/100 g WM).

Boiling the taro leaves resulted in a 36% loss of soluble oxalates, while the soluble oxalate content of baked tissue was very similar to the raw tissue. The mean insoluble oxalate content of the raw, boiled and baked tissue was 226.28 mg oxalate/100 g WM. Overall, boiling the taro leaves was an effective way of reducing the soluble oxalate content of the cooked tissue.     

Effect of thermal processing on retinol levels of free-range and caged hen eggs

Purpose Eggs are a food item of high nutritional value, a source of vitamin A and readily accessible to the general population.Methods This paper analysed the effect of cooking on the retinol levels of free-range and caged hen eggs, using high performance liquid chromatography (HPLC). The retinol levels of hen and quail eggs were also compared.Results The raw egg yolk retinol concentrations of free-range and caged hen eggs were 476.53+/-39.44 and 474.93+/-41.10 microg/100 g and cooked egg yolk concentrations were 393.53+/-24.74 and 379.01+/-30.78 microg/100 g, respectively; quail egg concentration was 636.56+/-32.71 microg retinol/100 g. No significant difference was found between the retinol of free-range and caged hen egg yolks; however, cooking diminished retinol levels, causing a loss of 17 and 20% in the free-range and caged hen egg yolks, respectively. Quail egg retinol concentration was significantly higher than that of the hens.Conclusion The retinol found in 100 g of hen and quail egg yolks could supply around 42 and 70.7% of the vitamin A requirements of an adult man, and is accordingly considered an excellent source of this vitamin.     

北京市常见食物熟制前后叶黄素和玉米黄素及β-胡萝卜素的含量比较

目的 测定北京市常见食品中叶黄素、玉米黄素和β-胡萝卜素的含量,并比较熟制后其含量的变化.方法 于2009年9-10月在北京市海淀区选取8类46种食物,使用高效液相色谱法对其熟制前后叶黄素、玉米黄素和β-胡萝卜素的含量进行检测.结果 茄果瓜菜类蔬菜、葱蒜类蔬菜和坚果中叶黄素含量丰富,其中韭菜(18 226.9μg/100 g)和甘栗南瓜(13 265.2μg/100 g)中含量较高.甘栗南瓜、蒜薹、玉米和蛋类中含有较丰富的玉米黄素,分别为444.6、283.5、279.7、118.6～377.9 μg/100 g,熟制后其含量分别改变为483.9、239.3、279.1、149.5～594.7μg/100 g;生韭菜中未检出玉米黄素,熟制后其玉米黄素含量达1081.2μg/100 g.β-胡萝卜素广泛存在于各种蔬菜水果中,其中胡萝卜中含量最高,达17 234.3 μg/100 g,熟制后其β-胡萝卜素含量变为17 013.5 μg/100 g.结论 选择性摄入不同种类食物及改变食物的加工制作方法将有利于增加膳食叶黄素、玉米黄素和β-胡萝卜素的摄入量.

Abstract：

Objective To measure lutein, zeaxanthin and β-carotene level in foods commonly consumed in Beijing,and compare the content difference between raw and cooked food. Methods Forty-six commonly consumed foods of 8 classes were collected in Haidian district of Beijing from September to October in 2009. A high performance liquid chromatography method was used to determine the content of lutein, zeaxanthin and β-carotene in both raw and cooked samples. Results Lutein was abundant in cucurbitaceous and solanaceous,alliums and nuts,especially in Chinese chive (18 226. 9 μg/100 g) and pumpkin (13 265.2 μg/100 g). Major sources of zeaxanthin included round pumpkin,green garlic shoot,corn and eggs, whose level of zeaxanthin were 444.6, 283.5, 279.7, 118.6-377.9 μg/100 g,respectively. Zeaxanthin level of those cooked foods changed to 483.9, 239. 3, 279. 1, 149. 5-594. 7 μg/100 g, respectively. The zeaxanthin level of cooked Chinese chive reached 1081.2 μg/100 g, while we did not detect any zeaxanthin in raw Chinese chive. β-carotene was present in a wide variety of vegetables and fruits. Carrot (17 234. 3 μg/100 g) was a good source of β-carotene,while its level in cooked carrot was 17 013.5 μg/100 g. Conclusion Consuming the proper kinds of foods and changing the method of food processing were beneficial to increase the intake of lutein, zeaxanthin and β-carotene.     

Effects of high level of vitamin C on tissue antioxidant status of guinea pigs.

Two groups of weanling male Hartley guinea pigs maintained on vitamin E deficient diet were supplemented with 0.4 I.U./100 g body weight/day of vitamin E and either 2 (Group A) or 10 (Group B) mg/100 g body weight/day of vitamin C for 5 weeks. As compared to Group A, the degree of erythrocyte hemolysis and liver TBAR level of Group B were significantly increased while plasma vitamin E and erythrocyte GSH levels were significantly decreased. In another experiment, two groups of guinea pigs were given 0.8 I.U./100 g body weight/day of vitamin E and 2 (Group C) or 30 mg/100 g body weight/day (Group D) of vitamin C. Levels of plasma vitamin E and erythrocyte GSH of Group D were significantly lower than those of Group C: however, erythrocyte hemolysis and liver TBAR were not affected by the level of vitamin C supplementation. The results suggest that the high levels of vitamin C supplementation lowered tissue antioxidant potential of animal when vitamin E was marginally adequate, and the hemolytic and peroxidizing effect of high level of vitamin C may be counteracted by increasing the level of vitamin E.