Hydrophilic Antioxidant Activity Research Articles

Phytonutrients affecting hydrophilic and lipophilic antioxidant activities in fruits, vegetables and legumes

AbstractThe antioxidant activities of fruits (n = 21), vegetables (n = 67) and legumes (n = 7) commonly consumed in Korea were determined by both the lipophilic antioxidant performance assay (LAP) and the hydrophilic oxygen radical absorbance capacity assay (ORAC). The LAP assay used the lipophilic radical initiator MeO‐AMVN [2,2′‐azobis(4‐methoxy‐2,4‐dimethylvaleronitrile)] and the lipophilic probe BODIPY 581/591 [4,4‐difluoro‐5‐(4‐phenyl‐1,3‐butadienyl)‐4‐bora‐3a, 4a‐diaza‐s‐indacene‐3‐undecanoic acid]. The ORAC assay used the hydrophilic radical initiator AAPH [2,2′‐azobis(2‐amidinopropane) dihydrochloride] and the hydrophilic probe fluorescein. In addition, the lipid‐soluble phytonutrients, carotenoids and tocopherols were determined by a reverse‐phase HPLC system using a C30 column with a UV detector. The water‐soluble phytonutrient, ascorbic acid, was analyzed using an HPLC system with an electrochemical detector. Total phenols were determined by UV spectrophotometry. Tocopherols (r = 0.774, p < 0.0001) and carotenoids (r = 0.569, p < 0.0001) were significantly correlated with LAP in total samples (n = 95). ORAC was significantly correlated with total phenols (r = 0.893, p < 0.0001), but not with ascorbic acid (r = 0.009, p = 0.929) in total samples (n = 95). These data indicate that carotenoids and tocopherols and total phenols are the major contributors to the lipophilic and hydrophilic antioxidant capacities, respectively. Therefore, the contribution of both the hydrophilic and lipophilic components of fruits and vegetables should be considered when determining the actual ‘total’ antioxidant activity of fruits and vegetables. Copyright © 2007 Society of Chemical Industry

Variation of lycopene, antioxidant activity, total soluble solids and weight loss of tomato during postharvest storage

The time between harvesting and consumption of fruit or vegetables could be up to several weeks. Phytochemical reactions in response to environmental conditions of harvested fruit or vegetables during this period may change the level of biological and medicinal activities of particular compounds. Therefore, quantification of such phytochemical reactions is a critical point in designing nutritional value studies. Red stage ripened cluster tomatoes ( Lycopersicon esculentum Mill. cv. Clermon) grown hydroponically in greenhouses were analyzed for variation of lycopene, hydrophilic antioxidant activity (using TEAC assay), total soluble solids and weight loss during two subsequent weeks of storing at 12 and 5 °C in comparison to 7 d room temperature storage as control. Low temperature storage at 5 °C in compare to 12 °C inhibited weight loss and enhancement of lycopene and TSS but antioxidant activity was increased as much as 1.77 times. Room temperature stored tomatoes showed significant increase in lycopene content and weight loss, but no effect on TSS and antioxidant activity during 7 d storage. TSS was not affected either by room temperature or low temperature storage, but weight loss, lycopene content and antioxidant activity at room temperature in compare to low temperature stored tomatoes were significantly different. It seems chilling stress shifts the pathways involved in the biosynthesis of antioxidant active compounds into higher levels of production. The results showed that postharvest environmental conditions need to be considered carefully for evaluation of particular bioactive compounds in fresh fruit and vegetables.

METHOD FOR DETERMINING TOTAL (HYDROPHILIC AND LIPOPHILIC) RADICAL-SCAVENGING ACTIVITY IN THE SAME SAMPLE OF FRESH PRODUCE

The work was aimed at developing a method for measuring hydrophilic and lipophilic antioxidant activities in the same sample of fresh fruits or vegetables. The assay was based on decolorization of 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) radical cation (ABTS + .). The radical was generated in acidified ethanol medium in order to allow the performance of both hydrophilic and lipophilic antioxidants. The radical generation conditions were optimized by choosing an appropriate acidifier, its concentration and incubation time. Hydrophilic and lipophilic fractions were isolated from fresh samples without preliminary drying by stepwise extraction with acetate buffer, acetone and hexane and repeated partition of water-soluble and water-insoluble portions. The method was applied to various fruits and vegetables. In avocado, the ratio between lipophilic and hydrophilic antioxidants varied from 1:1 to 1:3. In cherry tomatoes this ratio changed from 1:5 in green fruit to 1:1.5 in the red one. In strawberry, practically all antioxidant activity was represented by hydrophilic compounds. The total antioxidant activity in strawberries reached 14 μM TE (Trolox equivalents) per g, higher than in other objects tested.

Changes in hydrophilic antioxidant activity in Avena sativa and Triticum aestivum leaves of different age during de-etiolation and high-light treatment

The steady-state of reactive oxygen species (ROS) in plant cells is controlled by ROS-producing and scavenging agents. A large cellular pool of antioxidant metabolites is involved in their control. Variations in this antioxidant pool may be monitored by measuring changes in hydrophilic antioxidant activity (free radical-quenching activity of water-soluble components) and ascorbic acid levels. The de-etiolation process and induction of light stress in Avena sativa and Triticum aestivum leaves were used as physiological models to study the antioxidant status at different ages. The data showed that five-day-old green plants and de-etiolated plants of the same age have similar hydrophilic antioxidant activity ( approximately 8 mumol ASC equivalents g FW(-1)), which increases during the de-etiolation process. In oat and wheat, young leaves (five days old) had higher antioxidant status (hydrophilic antioxidant activity and ascorbic acid level) than old leaves (10 and 20 days old). High-light treatment caused a decrease in antioxidant status, especially in young leaves. Hydrophilic antioxidant activity and ascorbic acid levels recovered totally or partially after 30 or 60 min in the dark. This capacity also depends on age and species. The ascorbic acid/hydrophilic antioxidant activity ratio is presented as an indicator of antioxidant variations in response to stress, but taking into account the absolute levels of antioxidants.

Antioxidant Composition in Cherry and High-Pigment Tomato Cultivars

Fourteen cultivars of cherry tomatoes and four cultivars of high-pigment tomato hybrids were cultivated in southern Italy, and the red-ripe fruits were analyzed for their content in different classes of antioxidants and for their antioxidant activity. Among the different cultivars, significant differences were found between lycopene, beta-carotene, alpha-tocopherol, vitamin C (ascorbic acid and dehydroascorbic acid), and total phenolic and flavonoid contents. LS203 and Corbus appear to be the cultivars with the highest content of lipophilic and hydrophilic antioxidants among cherry tomatoes, respectively. All cultivars of high-pigment tomato hybrids showed an expected exceptionally high lycopene content. Among them, the highest content of lipophilic and hydrophilic antioxidants was found in cv. HLY 13. Hydrophilic and lipophilic antioxidant activities were both significantly influenced by genotype. Such results highlight an existing unexploited variability in tomato germplasm and stress the need to evaluate the biodiversity and to support conventional breeding programs to improve tomato nutritional value.

Hydrophilic and Lipophilic Antioxidant Activity in Different Leaves of Three Lettuce Varieties

Three different Lactuca sativa L. varieties (Iceberg, Romaine and Baby head) were analysed in order to determine differences in the antioxidant activity, both hydrophilic and lipophilic, and in the total phenolic content of different leaves (stem, inner, medium and outermost leaves). Romaine showed the highest level of hydrophilic and lipophilic antioxidant activity, and its phenolic content was also higher than that of Iceberg and Baby head. According to leaf position, lipophilic antioxidant activity increased sharply from stem to outermost leaves, suggesting a protective role for the lipophilic antioxidant in mature or light-exposed leaves, while hydrophilic antioxidant activity shows a non-specific distribution. The phenolic content also increased in Romaine from stem to outermost leaves, although no significant changes were observed in Iceberg or Baby head lettuces in this respect.

Rapid Peroxyl Radical Scavenging Capacity (PSC) Assay for Assessing both Hydrophilic and Lipophilic Antioxidants

This paper reports a simple, rapid, and sensitive assay for assessing peroxyl radical scavenging capacity (PSC) of both hydrophilic and lipophilic antioxidant compounds and food extracts. The assay is based on the degree of inhibition of dichlorofluorescin oxidation by antioxidants that scavenge peroxyl radicals, generated from thermal degradation of 2,2'-azobis(amidinopropane). For hydrophilic antioxidant activity, the dose required to cause a 50% inhibition of the reaction (EC(50)) ranged from 2.41 +/- 0.02 (EGCG) to 21.26 +/- 0.38 microM (ferulic acid). EC(50) values for the hydrophilic antioxidant activity of food extracts ranged from 309.2 +/- 3.63 (apple) to 3345.1 +/- 151.5 micromol of vitamin C equiv/100 g for wheat bran. The EC(50) values for lipophilic antioxidant activity were 1.58 +/- 0.11 (Trolox), 4.35 +/- 0.43 (alpha-tocopherol), 18.94 +/- 0.38 (BHA), and 182.69 +/- 13.7 microM (BHT). Whole grain lipophilic antioxidant activity ranged from 3.49 +/- 0.57 (wheat) to 8.79 +/- 1.98 micromol of alpha-tocopherol equiv/100 g of rice. Hydrophilic antioxidant activity contributed >98% of the total antioxidant activity (hydrophilic plus lipophilic) of whole grains tested. The PSC assay was accurate (86-108% recovery), precise (0.12-11% CV), and reproducible (12% RSD) and produced results comparable to those of similar published assays. The PSC assay can be routinely used to analyze or screen both hydrophilic and lipophilic antioxidants or food extracts and will be a valuable alternative biomarker for future epidemiological studies of chronic diseases.

Effects of cutting and maturity on antioxidant activity of fresh-cut tomatoes

To investigate the changes in total antioxidant activity of fresh-cut tomato during storage, tomato fruits harvested at three different stages of maturity were cut into 7-mm thick slices and stored at 5 °C. Intact fruits were stored in the same conditions as a control. The antioxidant activity was evaluated as the capacity to scavenge the radical ABTS + in both hydrophilic (HAA) and lipophilic (LAA) extracts. Cutting resulted in a decrease in the HAA compared to the control fruits and did not influence significantly the LAA. Changes in LAA during storage were described by a simple exponential model developing towards an asymptotic end value. The HAA also decreased exponentially in the beginning of the storage time but increased again afterwards. For both hydrophilic and lipophilic antioxidant activity the riper the fruit the higher was the antioxidant activity. Since no relevant interaction was found between time of storage and stage of maturity, the major factor determining the level of antioxidants in tomatoes seems to be the initial level of antioxidant activity at the moment of harvest. The levels of HAA did not differ significantly due to ripening during storage, while the LAA increased with ripening. These results indicate a potential effect of processing to decrease the antioxidant activity in vivo. This would represent a decrease in the value of cut tomatoes as a source of hydrophilic antioxidants in the diet compared with the fruit stored intact. In another experiment, realized at the same conditions, the total antioxidant activity was evaluated using a lipid peroxidation inhibition assay. Antioxidant activity could be measured in methanol extracts, but not in THF extracts. Aqueous extracts showed pro-oxidant activity. No effect of cutting or storage time was observed.

EFFECTS OF CUTTING AND MATURITY ON ANTIOXIDANT ACTIVITY OF FRESH-CUT TOMATOES

To investigate the changes in total antioxidant activity of fresh-cut tomato during storage, tomato fruits harvested at three different stages of maturity were cut into 7-mm thick slices and stored at 5°C. Intact (control) fruits were stored in the same conditions. The antioxidant activity was evaluated as the capacity to scavenge the radical ABTS + in both hydrophilic (HAA) and lipophilic (LAA) extracts. Cutting resulted in a decrease in the HAA compared to control fruits and did not influence significantly the LAA. Changes in LAA during storage were described by a simple exponential model developing towards an asymptotic end value. The HAA also decreased exponentially in the beginning of the storage time but increased again afterwards. The hydrophilic antioxidant activity was higher than the lipophilic antioxidant activity for all stages of maturity. The levels of HAA did not differ significantly due to ripening during storage while the LAA increased with ripening.

Cultivar Variation in Physicochemical and Antioxidant Activity of Alabama-Grown Blackberries

Abstract Blackberries are an excellent source of natural antioxidants. Fully ripened fruit of ‘Apache’, ‘Arapaho’, ‘Chester’, ‘Loch Ness’, ‘Navaho’ and ‘Triple Crown’ thornless blackberries were evaluated for their physicochemical and antioxidative activity. There were no consistent differences for variation in initial pH, titratable acidity (TA), total soluble sugar (TSS) and TSS/TA ratio values determined. Differences among cultivars with respect to reduced ascorbic acid (AA) were established, but there were no differences in either oxidized ascorbic acid (DHA) or total ascorbic acid (TAA) content. The antioxidant activity as determined by ABTS radical cation procedure for fractionated crude fruit extracts varied in response to parameters evaluated. Hydrophilic antioxidant activity (HAA) was not different among cultivars evaluated. In contrast, differences were found in lipophilic antioxidant activity (LAA) and total antioxidant activity (TAA).

Antioxidants in potato

The content of compounds in potato that may act as antioxidants in the human diet is not widely appreciated. Carotenoids are present in the flesh of all potatoes. The contents mentioned in the literature range from 50 to 100 μg per 100 g fresh weight (FW) in white-fleshed varieties to 2000 μg per 100 g FW in deeply yellow to orange-fleshed cultivars. The carotenoids in potato are primarily lutein, zexanthin, and violaxanthin, all of which are xanthophylls. There is just a trace of either alpha or beta-carotene, meaning that potato is not a source of pro-vitamin A carotenes. In potatoes with total carotenoids ranging from 35 to 795 μg per 100 g FW, the lipophilic extract of potato flesh presented oxygen radical absorbance capacity (ORAC) values ranging from 4.6 to 15.3 nmoles α-tocopherol equivalents per 100 g FW. Potatoes contain phenolic compounds and the predominant one is chlorogenic acid, which constitutes about 80% of the total phenolic acids. Up to 30 μg per 100 g FW of flavonoids are present in the flesh of white-fleshed potatoes with roughly twice the amount present in red and purple-fleshed potatoes. The predominant flavonoids are catechin and epicatechin. Red and purple potatoes derive their color from anthocyanins. The skin alone may be pigmented, or the flesh may be partially or entirely pigmented. Whole unpeeled with complete pigmentation in the flesh may have up to 40 mg per 100 g FW of total anthocyanins. Red-fleshed potatoes have acylated glucosides of pelargonidin while purple potatoes have, in addition, acylated glucosides of malvidin, petunidin, peonidin, and delphinidin. The hydrophilic antioxidant activity of solidly pigmented red or purple potatoes is comparable to brussels sprouts or spinach. In red and purple potatoes with solidly pigmented flesh with levels of total anthocyanin ranging from 9 to 38 mg per 100 g FW, ORAC ranged from 7.6 and 14.2 umole per g FW of Trolox equivalents. Potato contains on average 20 mg per 100 g FW of vitamin C, which may account for up to 13 % of the total antioxidant capacity. Potatoes should be considered vegetables that may have high antioxidant capacity depending on the flesh composition.

Phytochemicals and Antioxidant Activity of Milled Fractions of Different Wheat Varieties

The health-promoting effects of whole-grain consumption have been attributed in part to their unique phytochemical contents and profiles that complement those found in fruits and vegetables. Wheat is an important component of the human diet; however, little is known about the phytochemical profiles and total antioxidant activities of milled fractions of different wheat varieties. The objectives of this study were to investigate the distribution of phytochemicals (total phenolics, flavonoids, ferulic acid, and carotenoids) and to determine hydrophilic and lipophilic antioxidant activity in milled fractions (endosperm and bran/germ) of three different wheat varieties, two of which were grown in two environments. Grain samples of each of the wheat varieties were milled into endosperm and bran/germ fractions. Each fraction was extracted and analyzed for total phenolics, ferulic acid, flavonoids, carotenoid contents, and hydrophilic and lipophilic antioxidant activities. Total phenolic content of bran/germ fractions (2867-3120 micromol of gallic acid equiv/100 g) was 15-18-fold higher (p < 0.01) than that of respective endosperm fractions. Ferulic acid content ranged from 1005 to 1130 micromol/100 g in bran/germ fractions and from 15 to 21 micromol/100 g in the endosperm fractions. The bran/germ fraction flavonoid content was 740-940 micromol of catechin equiv/100 g. On average, bran/germ fractions of wheat had 4-fold more lutein, 12-fold more zeaxanthin, and 2-fold more beta-cryptoxanthin than the endosperm fractions. Hydrophilic antioxidant activity of bran/germ samples (7.1-16.4 micromol of vitamin C equiv/g) was 13-27-fold higher than that of the respective endosperm samples. Similarly, lipophilic antioxidant activity was 28-89-fold higher in the bran/germ fractions (1785-4669 nmol of vitamin E equiv/g). Hydrophilic antioxidant activity contribution to the total antioxidant activity (hydrophilic + lipophilic) was >80%. In whole-wheat flour, the bran/germ fraction contributed 83% of the total phenolic content, 79% of the total flavonoid content, 51% of the total lutein, 78% of the total zeaxanthin, 42% of the total beta-cryptoxanthin, 85% of the total hydrophilic antioxidant activity, and 94% of the total lipophilic antioxidant activity. Our results showed that different milled fractions of wheat have different profiles of both hydrophilic and lipophilic phytochemicals. These findings provide information necessary for evaluating contributions to good health and disease prevention from whole-wheat consumption.

266 ANTIOXIDANT CAPACITY OF BOAR SEMINAL PLASMA

It has been established that antioxidants in seminal plasma play an important role in protecting the spermatozoa against oxidative stress-induced damage. This study was conducted to measure the total antioxidant capacity (TAC) of boar seminal plasma. Fifty-four ejaculates were collected from 17 mature boars of proven fertility by the gloved-hand technique. Ejaculates were collected separately in different fractions (pre-sperm, sperm-rich, and post-sperm) according to their macroscopic (color) characteristics. After centrifugation (2400g for 3 min), the sperm pellet was discarded; the supernatant was recentrifuged and filtered through a 10-μm nylon mesh filter to remove debris or clumped spermatozoa. The seminal plasma was frozen at -20°C until further use. After thawing at room temperature, seminal plasma aliquots of 5 μL were immediately assessed for total antioxidant capacity. TAC was measured using the ABTS/H2O2/HRP decoloration method (Cano A et al. 2000 Redox Report 5, 365–370) which allows differentiation between hydrophilic and lipophilic antioxidant activity capacity. TAC units were expressed as micromolar (μM) Trolox equivalents. Data were analyzed using ANOVA. Only the hydrophilic activity was measurable, with the lipophilic activity being undetected. The overall TAC of seminal samples (mean ± SEM) was 1623.7 ± 56.28 μM, ranging from 674 to 2428 μM. Different TACs were observed among males (P &lt; 0.05) and between ejaculates of the same male (P &lt; 0.05). Ejaculate fraction had a significant effect (P &lt; 0.001) on the TAC levels. The post-sperm fraction had a significantly lower TAC level (1104.09 ± 57.66 μM) than the pre-sperm and sperm-rich fractions (1611.95 ± 153.68 μM and 1356.136 ± 72.47 μM, respectively, P &lt; 0.001). In conclusion, hydrophilic antioxidant activity represented the main contribution to the TAC in boar seminal plasma, showing differences among males, between ejaculates of the same male, and also between the different ejaculate fractions. This work was supported by CICYT (AGF98-0533; AGL01-0471) and INIA (RZ01-019).

A Comparison of Carotenoid Content and Total Antioxidant Activity in Catsup from Several Commercial Sources in the United States

Samples of catsup from 13 commercial sources, representing at least 10 U.S. manufacturers, were analyzed for carotenoid content, antioxidant activity, and percentage solids. The solids content of these catsup brand samples varied from 26.31 to 38.06% solids. The lycopene content ranged from 59.42 to 183.36 microg, and total carotenoids were as high as 216.6 microg/g fresh weight, respectively. In addition, both hydrophilic and lipophilic antioxidant activities were measured using the Trolox equivalent antioxidant capacity (TEAC) assay. These measurements of samples of the various catsup brands ranged from 176.5 to 356.8 total TEAC units.

Physicochemical and Antioxidant Changes in Six Alabama-grown Blackberry Cultivars

Blackberries are an excellent source of natural antioxidants. Fully ripened fruit of `Apache', `Arapaho', `Chester', `Loch Ness', `Navaho', and `Triple Crown' thornless blackberries were evaluated for their physicochemical and antioxidative activity. Differences in initial pH, titratable acidity (TA), total soluble solids (TSS), TSS/TA ratio and soluble sugars (reducing sugar, sucrose, and total sugars) differed among cultivars. Differences among cultivars with respect to reduced ascorbic acid (AA) were established, but there were no differences in either oxidized ascorbic acid (DHA) or total ascorbic acid (TAA) content. Antioxidant activity was determined by ABTS radical cation procedure for fractionated crude fruit extracts and the cultivars varied in the parameters evaluated. Hydrophilic antioxidant activity (HAA) was not different among cultivars evaluated. In contrast, lipophilic antioxidant activity (LAA) and total antioxidant activity (TAA) differed. The results obtained in this study indicate that Alabama-grown blackberries vary in their quality indices and are an excellent source of natural antioxidants. Information compiled will assist in marketing, handling, postharvest storage of these fruit and serve as a guide to partial fulfillment of recommended daily dietary requirements.

ACTIVIDAD ANTIOXIDANTE HIDROFÍLICA Y LIPOFÍLICA Y CONTENIDO EN VITAMINA C DE ZUMOS DE NARANJA COMERCIALES: RELACIÓN CON SUS CARACTERÍSTICAS ORGANOLÉPTICASLIPOPHILIC AND HYDROPHILIC ANTIOXIDANT ACTIVITY AND VITAMIN C CONTENT OF COMMERCIAL ORANGE JUICES: CORRELATION WITH ORGANOLEPTIC PARAMETERSACTIVIDADE ANTIOXIDANTE HIDROFÍLICA E LIPOFÍLICA E CONTIDO EN VITAMINA C DE ZUMOS DE LARANXA COMERCIAIS: RELACIÓN COAS CARACTERÍSTICAS ORGANOLÉPTICAS

One of the beneficial qualities of fruits and vegetables with high acceptation among consumers are their antioxidant properties. Basically, an antioxidant is defined as a compound that is able to neutralize and protect a biological system against free radicals, such as oxygen, nitrogen and lipidic radicals. In this work, the relationship between antioxidant activity of commercial orange juices and the vitamin C (ascorbic acid) levels are studied. A study on the contribution of lipophilic and hydrophilic compounds to the total antioxidant activity were also carried out. The results showed that pasteurized juices have lower levels of antioxidant activity than refrigerated ones, and the ratio vitamin C/antioxidant activity can be useful as indicator of the type of juice. More than 98% of the total antioxidant activity (TAA) in orange juices is due to the hydrophilic activity being the lipophilic one lower than 2%. Finally, the correlations among the hydrophilic antioxidant activity of commercial juices and some organoleptic parameters (color, flavor and taste) are presented. © 2004 Altaga. All rights reserved. Resumen Una de las cualidades beneficiosas cada vez más valorada en las frutas y las hortalizas por los consumidores es su actividad o propiedades antioxidantes. Generalmente, un antioxidante se puede definir como aquella sustancia natural o artificial con capacidad para neutralizar y proteger a un sistema biológico frente a radicales libres, tales como los radicales de oxígeno, los de nitrógeno y los radicales lipídicos. En este trabajo se estudia la relación existente entre la Activadad Antioxidante de zumos de naranja comerciales de distintos tipos y su contenido en vitamina C (ácido ascórbico). También se realiza un estudio sobre la aportación de los componentes hidrofilicos y lipofilicos del zumo a la Actividad Antioxidante Total (AAT) del producto. Los resultados muestran que los zumos pasteurizados poseen, en general, menores valores de actividad antioxidante que los refrigerados y que la relación vitamina C/actividad antioxidante puede ser utilizada como indicador del tipo de zumo. Más del 98% de la AAT de los zumos está constituida por la Actividad Antioxidante Hidrofílica (AAH) siendo la Actividad Antioxidante Lipofílica (AAL) menor al 2%. Por último, se presenta la correlación existente entre la AAH de los zumos comerciales con parámetros organolépticos (color, sabor, aroma) obtenidos a través de una cata entre personal de la Universidad de Murcia. © 2004 Altaga. Todos los derechos reservados. Palabras clave: Ácido ascórbico, antioxidantes, cítricos, naranja, vitamina C, zumos Resumo Unha das cualidades beneficiosas cada vez máis valorada nas froitas e nas hortalizas polos consumidores é a súa actividade ou propiedades antioxidantes. Xeralmente, un antioxidante pódese definir como aquela sustancia natural ou artificial con capacidade para neutralizar e protexer a un sistema biolóxico fronte a radicais libres, tales como os radicais de oxíxeno, os de nitróxeno e os radicais lipídicos. Neste traballo estúdiase a relación existente entre a Actividade Antioxidante de zumes de laranxa comerciais de distintos tipos e o seu contido en vitamina C (ácido ascórbico). Tamén relízase un estudio sobre a aportación dos compoñentes hidrofílicos e lipofílicos do zume á Actividade Antioxidante Total (AAT) do producto. Os resultados mostran que os zumes pasteurizados posúen, en xeral, menores valores de actividade antioxidante que os refrixerados e que a relación vitamina C/actividade antioxidante pode ser empregada como indicador do tipo de zume. Máis do 98% da AAT dos zumes está constituida pola Actividade Antioxidante Hidrofílica (AAH) sendo a Actividade Antioxidante Lipofílica (AAL) menor ó 2%. Por último, preséntase a correlación existente entre a AAH dos zumes comerciais con parámetros organolépticos (color, sabor, aroma) obtidos a través dunha cata entre personal da Universidade de Murcia. © 2004 Altaga. Tódolos dereitos reservados. Palabras chave: Acido ascórbico, antioxidantes, cítricos, laranxa, vitamina C, zumes

Bioactive proteins and peptides from food sources. Applications of bioprocesses used in isolation and recovery.

There are many examples of biologically active food proteins, with physiological significance beyond the pure nutritional requirements that concern available nitrogen for normal growth and maintenance. Moreover, there are many physiologically active peptides, derived by protease activity from various food protein sources; however, relationships between structural properties and functional activities have not been completely elucidated. Many bioactive peptides have in common structural properties that include a relatively short peptide residue length (e.g. 2-9 amino acids), possessing hydrophobic amino acid residues in addition to proline, lysine or arginine groups. Bioactive peptides are also resistant to the action of digestion peptidases. Antihypertensive peptides, known as Angiotensin I converting enzyme (ACE) inhibitors have been derived from milk, corn and fish protein sources. Peptides with opioid activities are derived from wheat gluten or casein, following digestion with pepsin. Exorphins, or opioid peptides derived from food proteins such as wheat and milk (e.g. exogenous sources) have similar structure to endogenous opioid peptides, with a tyrosine residue located at the amino terminal or bioactive site. Immunomodulatory peptides derived from tryptic hydrolysates of rice and soybean proteins act to stimulate superoxide anions (reactive oxygen species-ROS), which triggers non-specific immune defense systems. Antioxidant properties that prevent peroxidation of essential fatty acids have also been shown for peptides derived from milk proteins. The addition of a Leu or Pro residue to the N-terminus of a His-His, dipeptide will enhance antioxidant activity and facilitate further synergy with non-peptide antioxidants (e.g. BHT). We also show herein, that the tryptic digests of casein yielding caseinophosphopeptides exhibits both hydrophilic and lipophilic antioxidant activity due to both metal ion sequestering and quenching of ROS. The separation and purification of bioactive peptides which will involve development of automated and continuous systems is an important field for Food chemists. Much effort has been given to develop selective column chromatography methods that can replace batch methods of salting out, or using solvent extraction to isolate and purify bioactive peptides. Advances here will enable recovery of bioactive peptides with minimal destruction thus enabling utilization by returning these active peptides to functional food or specific nutraceutical applications.

Free radical-scavenging activity of indolic compounds in aqueous and ethanolic media

Indolic compounds are a broad family of substances present in microorganisms, plants and animals. They are mainly related with tryptophan metabolism, and present particularities that depend on their respective chemical structures. The most important members of the family are the plant hormone, indole-3-acetic acid, and the animal hormone, melatonin. An important characteristic of some indolic compounds is that they may be useful as chemical preventive agents against diseases such as cancer, oxidative stress, etc. For this reason, the possible antioxidant activities (free radical-scavenging activity) of several indoles were studied. The2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid /H(2)O(2)/HRP decoloration method was applied to determine both hydrophilic (in buffered media) and lipophilic (in organic media) antioxidant properties of the indolic compounds. Also, a study of the hydrophilic antioxidant activities of indoles at different pH values (between 4.5 and 8.5) was made. Finally, their possible role as diet plant antioxidants is discussed.

Hydrophilic and lipophilic antioxidant activity changes during on-vine ripening of tomatoes (Lycopersicon esculentum Mill.)

Changes in antioxidant activity during the on-vine ripening of tomatoes (Lycopersicon esculentum) were studied at four different ripening stages (green, breaker, pink and red ripe). Hydrophilic and lipophilic antioxidant activities (HAA and LAA, respectively) were determined and their relationships to ascorbic acid, total phenols, lycopene and β-carotene contents were analysed. HAA and ascorbic acid remained practically unchanged, while the levels of aqueous phenols increased during ripening. The levels of ascorbic acid and HAA were strongly correlated (r=0.90, P<0.1). β-Carotene increased until breaker and pink stages, decreasing afterwards. In contrast, lycopene accumulated throughout the ripening period. The LAA followed the same pattern as lycopene and a good correlation was found (r=0.91, P<0.05). There was less difference between the measured and calculated LAA as the lycopene level increased, the discrepancy being lowest at the red-ripe stage, indicating the importance of lycopene as a lipophilic antioxidant in tomatoes.

Hydrophilic and lipophilic antioxidant activities of grapes.

The 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid)/H2O2/horseradish peroxidase (ABTS/H2O2/HRP) decoloration method permits the evaluation of the antioxidant activity of complex food samples. This method is capable of determining both hydrophilic (in buffered media) and lipophilic (in organic media) antioxidant properties in the same sample. Its application to the study of the antioxidant properties of grapes, one white and two black, has permitted us to establish important differences in the antioxidant activity. The black grapes showed higher antioxidant activity than the white variety. The determination of hydrophilic antioxidant activity (HAA) and lipophilic antioxidant activity (LAA) in the three grapes showed that a minor contribution (4-13%) of total antioxidant activity (TAA) was due to LAA in all cases. The experimentally determined HAA could be approximated using the relative contributions of the calculated values of reference compounds (total phenols as gallic acid and anthocyanins as malvidin).