Archive

Research Area: Nutrient and Bioactive Composition

Polyphenol content and antioxidant activity of California almonds depend on cultivar and harvest year.

Bolling, B.W., G. Dolnikowski, J.B. Blumberg, C.-Y. O. Chen, 2010. Polyphenol content and antioxidant activity of California almonds depend on cultivar and harvest year. Food Chem. 122:819-825.

The polyphenol content and antioxidant activity of Nonpareil, Carmel, Butte, Sonora, Fritz, Mission, and Monterey almond cultivars harvested over three seasons in California were examined. LC–MS was employed to quantify 16 flavonoids and two phenolic acids in acidified methanol extracts of almond skins. The 3-year mean polyphenol content of cultivars ranged from 4.0 to 10.7 mg/100 g almonds. Isorhamnetin-3-O-rutinoside was the most abundant flavonoid, present at 28–49% of total polyphenols among cultivars. Almonds from 2006 and 2007 had 13% fewer polyphenols than 2005, but FRAP and total phenols were comparable. Cultivar, but not season, had a differential impact on individual polyphenol synthesis. Using the results of polyphenol, total phenol, and FRAP, multivariate analysis distinguished harvest years and most cultivars with 80% confidence. Flavonoid content and antioxidant activity of almonds may be more dependent on cultivar than on seasonal difference

Targeted analysis of conjugated and microbial-derived phenolic metabolites in human urine after consumption of an almond skin phenolic extract.

Garrido, I., M. Urpi-Sarda, M. Monagas, C. Gómez-Cordovés, P.J. Martín-Álvarez,  R. Llorach, B. Bartolomé, C. Andrés-Lacueva, 2010. Targeted analysis of conjugated and microbial-derived phenolic metabolites in human urine after consumption of an almond skin phenolic extract. J. Nutr. 140:1799–807.

A single-blind, placebo-controlled, and randomized trial study was carried out with 16 healthy volunteers (7 men and 5 women). The test group ingested an encapsulated almond skin phenolic extract (884 mg of total polyphenols/dose) containing flavan-3-ols, flavonols, and flavanones, whereas the placebo group ingested microcrystalline cellulose. Our aim in this study was to determine changes in the urinary excretion of conjugated and microbial-derived phenolic metabolites before (-2 to 0 h) and after (0–2, 2–6, 6–10, and 10–24 h) intake of the almond polyphenols compared with the placebo group. For the test group, maximum urinary excretion of (epi)catechin and naringenin conjugates derived from phase II metabolism was attained at 2–6 h after consumption of the almond skin extract and excretions differed from the placebo group during this time period (P ≤ 0.0001). However, excretion of conjugated metabolites of isorhamnetin was highest at 10–24 h and did not differ from the placebo group during this time (P > 0.05). Hydroxyphenylvalerolactones reached maximum urinary levels at 6–10 h after consumption of almond polyphenols, and excretion differed from the placebo group during this time period (P = 0.0004). For the test group, excretions of phenolic acids (hydroxyphenylpropionic, hydroxyphenylacetic, hydroxybenzoic, and hydroxycinnamic acids) did not differ from the placebo group at any time period of urine collection (P > 0.05). The findings presented in this work provide evidence concerning the bioavailability of almond skin polyphenols considering the effects of both phase II and microbial metabolism.

Characterization of polyphenols, lipids and dietary fibre from almond skins (Amygdalus communis L.).

Mandalari, G., A. Tomaino, T. Arcoraci, M. Martorana, V. Lo Turco, F. Cacciola, G.T. Rich, C. Bisignano, A. Saija, P. Dugo, K.L. Cross, M.L. Parker, K.W. Waldron, M.S. J. Wickham, 2010. Characterization of polyphenols, lipids and dietary fibre from almond skins (Amygdalus communis L.). Journal of Food Composition and Analysis. 23:166–174.

Almond skins and blanch water are underutilized by-products of the almond processing industry. Nevertheless, they contain exploitable components that may contribute to the health benefits associated with almond consumption. We have compared natural almond skin powder (NS) prepared by a novel freeze-thawing method with blanched almond skin powder (BS). Microstructural studies were carried out, and we analyzed both types of almond skin for phenolic compounds (by HPLC), lipids (by solvent extraction), proteins (by micro-Kjeldahl), and fibre content (by the enzymatic-gravimetric AOAC method). Antioxidant activity (by measuring the reduction of the 2,2-diphenyl-1-picrylhydrazyl radical) was also monitored. We identified a combination of flavonols, flavan-3-ols, hydroxybenzoic acids and flavanones in NS, BS and in industrially obtained blanch water (BW). As expected, the total phenolic content was higher in NS compared to BW and BS, although the latter showed high antioxidant properties. Almond skins had high fibre content as well as significant amounts of lipid; both of these components may be relevant to fermentation in the large intestine. In addition, the processing of almond skins and blanch water clearly has economic potential for lowering the environmental impact of waste fill and pollution.

Almond (Prunus dulcis (Mill.) D.A. Webb) polyphenols: From chemical characterization to targeted analysis of phenolic metabolites in humans.

Bartolomé, B., M. Monagas, I. Garrido, C. Gómez-Cordovés, P.J. Martín-Álvarez, R. Lebrón-Aguilar, M. Urpí-Sardà, R. Llorach, C. Andrés-Lacueva, 2010. Almond (Prunus dulcis (Mill.) D.A. Webb) polyphenols: From chemical characterization to targeted analysis of phenolic metabolites in humans. Archives of Biochemistry and Biophysics. 501:124–133.

In this paper, a survey of our studies on almond polyphenols including their chemical characterization and further bioavailability in humans is reported. Combination of analytical techniques (LC-DAD/fluorescence, LC/ESI-MS and MALDI-TOF-MS) allowed us, for the first time, the identification of A- and B-type procyanidin, propelargonidin and prodelphinidin polymers in almond skins. Glucuronide, O-methyl glucuronide, sulfate and O-methyl sulfate derivatives of (epi)catechin, as well as the glucuronide conjugates of naringenin and isorhamnetin, and sulfate conjugates of isorhamnetin, together with conjugates of hydroxyphenylvalerolactones were detected in plasma and urine samples after the intake of almond skin polyphenols. In addition, numerous microbial-derived metabolites, including hydroxyphenylpropionic, hydroxyphenylacetic, hydroxycinnamic, hydroxybenzoic and hydroxyhippuric acids were also identified. Depending of the type of metabolite, maximum urinary excretion was attained at different time in comparison to the control group in the course of the 24-h period of urine excretion, allowing us to establish the onset of microbial metabolism.

Functional lipid characteristics, oxidative stability, and antioxidant activity of macadamia nut (Macadamia integrifolia) cultivars.

Wall, M.M., 2010. Functional lipid characteristics, oxidative stability, and antioxidant activity of macadamia nut (Macadamia integrifolia) cultivars.  Food Chemistry. 121:1103–1108.

Phytochemical compounds (tocopherols, tocotrienols, and squalene) were measured in seven macadamia cultivars harvested from four locations on Hawaii island to establish whether these compounds enhance the oxidative stability of roasted kernels. Cultivars that had the greatest oxidative stability also had high total lipid-soluble antioxidant capacity. Tocopherols [delta (δ), gamma (γ), alpha (α)] were not detected in most macadamia nut samples, but macadamia kernels contained significant amounts of tocotrienols (31–92 µg/g oil) and squalene (72–171 µg/g oil) for all cultivars tested. This is the first report of variation for three tocotrienol homologs (δ-, γ-, α-T3) and total antioxidant capacity in macadamia nut cultivars. No statistical correlations were found between oxidative stability and tocopherol, tocotrienol, and squalene concentrations. However, two cultivars (HAES 294 and HAES 835) were identified with superior oxidative stability, suggesting that the kernel quality of these cultivars is more stable during storage.

Identification of the 100 richest dietary sources of polyphenols: an application of the Phenol-Explorer database.

Pérez-Jiménez, J., V. Neveu, F. Vos, A. Scalbert, 2010. Identification of the 100 richest dietary sources of polyphenols: an application of the Phenol-Explorer database. European Journal of Clinical Nutrition. 64: S112–S120.

Background/Objectives: The diversity of the chemical structures of dietary polyphenols makes it difficult to estimate their total content in foods, and also to understand the role of polyphenols in health and the prevention of diseases. Global redox colorimetric assays have commonly been used to estimate the total polyphenol content in foods. However, these assays lack specificity. Contents of individual polyphenols have been determined by chromatography. These data, scattered in several hundred publications, have been compiled in the Phenol-Explorer database. The aim of this paper is to identify the 100 richest dietary sources of polyphenols using this database. Subjects/Methods: Advanced queries in the Phenol-Explorer database (www.phenol-explorer.eu) allowed retrieval of information on the content of 502 polyphenol glycosides, esters and aglycones in 452 foods. Total polyphenol content was calculated as the sum of the contents of all individual polyphenols. These content values were compared with the content of antioxidants estimated using the Folin assay method in the same foods. These values were also extracted from the same database. Amounts per serving were calculated using common serving sizes. Results: A list of the 100 richest dietary sources of polyphenols was produced, with contents varying from 15 000mg per 100g in cloves to 10mg per 100 ml in rose´ wine. The richest sources were various spices and dried herbs, cocoa products, some darkly coloured berries, some seeds (flaxseed) and nuts (chestnut, hazelnut) and some vegetables, including olive and globe artichoke heads. A list of the 89 foods and beverages providing more than 1mg of total polyphenols per serving was established. A comparison of total polyphenol contents with antioxidant contents, as determined by the Folin assay, also showed that Folin values systematically exceed the total polyphenol content values. Conclusions: The comprehensive Phenol-Explorer data were used for the first time to identify the richest dietary sources of polyphenols and the foods contributing most significantly to polyphenol intake as inferred from their content per serving.

Chronic and acute effects of walnuts on antioxidant capacity and nutritional status in humans: a randomized, cross-over pilot study.

McKay, D.L., C.-Y. O. Chen, K.-J. Yeum, N.R. Matthan, A.H. Lichtenstein, J.B. Blumberg, 2010. Chronic and acute effects of walnuts on antioxidant capacity and nutritional status in humans: a randomized, cross-over pilot study. Nutrition  Journal. 9:21-30.

Background: Compared with other common plant foods, walnuts (Juglans regia) are consistently ranked among the highest in antioxidant capacity. In vitro, walnut polyphenols inhibit plasma and LDL oxidation, while in animal models they lower biomarkers of oxidative stress and raise antioxidant capacity. A limited number of human feeding trials indicate that walnuts improve some measures of antioxidant status, but not others. Methods: A 19 wk, randomized crossover trial was conducted in 21 generally healthy men and postmenopausal women ≥50 y to study the dose-response effects of walnut intake on biomarkers of antioxidant activity, oxidative stress, and nutrient status. Subjects were randomized to receive either 21 or 42 g raw walnuts/d during each 6 wk intervention phase with a 6 wk washout between phases. Subjects were instructed to consume their usual diet, but refrain from eating any other tree nuts, seeds, peanuts, or ellagitannin-rich foods during the entire study, and other polyphenol-rich foods for 2 d prior to each study visit. Results: Compared to baseline levels, red blood cell (RBC) linoleic acid and plasma pyridoxal phosphate (PLP) were significantly higher after 6 wk with 42 g/d walnuts (P < 0.05 for both). Overall, changes in plasma total thiols, and other antioxidant biomarkers, were not significant with either walnut dose. However, when compared to fasting levels, plasma total thiols were elevated within 1 h of walnut consumption with both doses during the baseline and end visits for each intervention phase (P < 0.05 for all). Despite the observed increase in RBC linoleic and linolenic acids associated with walnut consumption, this substrate for lipid peroxidation only minimally affected malondialdehyde (MDA) and antioxidant capacity. The proportional changes in MDA and Oxygen Radical Absorbance Capacity (ORAC) were consistent with a dose-response effect, although no significant within- or between-group differences were observed for these measures. Conclusions: Walnut consumption did not significantly change the plasma antioxidant capacity of healthy, well-nourished older adults in this pilot study. However, improvements in linoleic acid and pyridoxal phosphate were observed with chronic consumption, while total plasma thiols were enhanced acutely. Future studies investigating the antioxidant effects of walnuts in humans are warranted, but should include either a larger sample size or a controlled feeding intervention.

Antioxidant activity and phenolic profile of pistachio (Pistacia vera L., variety Bronte) seeds and skins

Tomaino, A., M. Martorana, T. Arcoraci, D. Monteleone, C. Giovinazzo, A. Saija, 2010. Antioxidant activity and phenolic profile of pistachio (Pistacia vera L., variety Bronte) seeds and skins. Biochimie. 92(9):1115-1122.

Pistachio (Pistacia vera L.; Anacardiaceae) is native of aride zones of Central and West Asia and distributed throughout the Mediterranean basin. In Italy, a pistachio cultivar of high quality is typical of Bronte (Sicily), an area around the Etna volcano, where the lava land and climate allow the production of a nut with intense green colour and aromatic taste, very appreciated in international markets. Pistachio nuts are a rich source of phenolic compounds, and have recently been ranked among the first 50 food products highest in antioxidant potential. Pistachio nuts are often used after removing the skin, which thus represents a significant by-product of pistachio industrial processing. The present study was carried out to better characterize the phenolic composition and the antioxidant activity of Bronte pistachios, with the particular aim to evaluate the differences between pistachio seeds and skins. The total content of phenolic compounds in pistachios was shown to be significantly higher in skins than in seeds. By HPLC analysis, gallic acid, catechin, eriodictyol-7-O-glucoside, naringenin-7-O-neohesperidoside, quercetin-3-O-rutinoside and eriodictyol were found both in pistachio seeds more than in skins; furthermore, genistein-7-O-glucoside, genistein, daidzein and apigenin appeared to be present only in pistachio seeds, while epicatechin, quercetin, naringenin, luteolin, kaempferol, cyanidin-3-O-galactoside and cyanidin-3-Oglucoside are contained only in pistachio skins. The antioxidant activity of pistachio seeds and skins was determined by means of four different assays (DPPH assay, Folin-Ciocalteau colorimetric method and TEAC assay, SOD-mimetic assay). As expected on the basis of the chemical analyses, pistachio skins have been shown to possess a better activity with respect to seeds in all tests. The excellent antioxidant activity of pistachio skins can be explained by its higher content of antioxidant phenolic compounds. By HPLC-TLC analysis, gallic acid, catechin, cyanidin-3-O-galactoside, eriodictyol-7-O-glucoside and epicatechin appeared to be responsible for the antioxidant activity of pistachio skin, together with other unidentified compounds. In conclusion, our work has contributed to clarify some particular characteristics of Bronte pistachios and the specific antioxidant power of pistachio skins. Introduction of pistachios in daily diet may be of undoubted utility to protect human health and well-being against cancer, inflammatory diseases, cardiovascular pathologies and, more generally, pathological conditions related to free radical overproduction. On the other hand, pistachio skins could be successfully employed in the food, cosmetic and pharmaceutical industries.

The influence of roasting, pasteurisation, and storage on the polyphenol content and antioxidant capacity of California almond skins

Bolling, B.W., J.B. Blumberg, C.-Y.O. Chen. 2010. The influence of roasting, pasteurisation, and storage on the polyphenol content and antioxidant capacity of California almond skins. Food Chem.doi:10.1016/j. foodchem.2010.05.058.

Polyphenols and antioxidant activity of skins from California almonds subjected to roasting, pasteurisation, and storage were determined by LC-MS quantification, total phenols (TP), and ferric reducing antioxidant power (FRAP). Pasteurisation did not significantly change TP, FRAP, or flavonoids and phenolic acids (FP). Roasted almonds had 26% less TP and 34% less FRAP than raw, but equivalent FP (n = 12). Storing almonds at 4 and 23 ºC for 15 mo resulted in gradual increases in FP, up to 177% and 200%, respectively (n = 13). At 4 ºC and 15 mo, polyphenols increased 18-fold for p-hydroxybenzoic acid, whilst others were 45–200% higher compared to baseline values. Isorhamnetin-3-O-rutinoside accounted for 48% of the increase in FP. After 15 mo, FRAP and TP increased to 200% and 190% of initial values. Accelerated ageing of whole almonds increased FP content by 10% after 3 days, but TP and FRAP values were not significantly different from baseline to day 10. Thus, in almond skins, roasting decreases TP and FRAP but not FP, whilst storage for up to 15 mo doubles F

In vitro evaluation of the prebiotic properties of almond skins (Amygdalus communis L.)

Mandalari, G., R.M. Faulks, C. Bisignano, K.W. Waldron, A. Narbad, M.S.J. Wickham. 2010. In vitro evaluation of the prebiotic properties of almond skins (Amygdalus communis L.). FEMS Microbiol. Lett.304:116-122.

In this study we investigated the potential prebiotic effect of natural (NS) and blanched (BS) almond skins, the latter being a byproduct of the almond-processing industry. A full model of the gastrointestinal tract, including in vitro gastric and duodenal digestion, followed by colonic fermentation using mixed fecal bacterial cultures, was used. Both NS and BS significantly increased the population of bifidobacteria and Clostridium coccoides/Eubacterium rectale group, resulting in a prebiotic index (3.2 for BS and 3.3 for NS) that compared well with the commercial prebiotic fructo-oligosaccharides (4.2) at a 24-h incubation. No significant differences in the proportion of gut bacteria groups and in short-chain fatty acid production were detected between NS and BS, showing that polyphenols present in almond skins did not affect bacterial fermentation. In conclusion, we have shown that dietary fiber from almond skins altered the composition of gut bacteria and almond skins resulting from industrial blanching could be used as potential prebiotics.