1a. Objectives (from AD-416)
1. Identify and quantify the flavonoid content of: blueberries, cranberries, and grapes; almonds, pistachios, and walnuts; and cocoa-based foods and contribute to future updates of the USDA Database for the Flavonoid Content of Selected Foods. 2. Determine tissue bioavailability and chemopreventive properties of anthocyanin-rich extracts of blueberries, cranberries, and grapes in a mouse model. 3. Investigate the effect of age on quercetin bioavailability and metabolism due to changes in phase II enzyme activity. 4. Test whether exposure of rat dams to a “Western” diet during pregnancy and lactation will increase obese phenotypes in their pups and whether dietary flavonoids, particularly isoflavones, will decrease the obese phenotype.
1b. Approach (from AD-416)
Using advanced chromatographic methods, we will measure the flavonoid content and evaluate the total antioxidant capacity of selected plant foods and the influence of geographical regions, agricultural practices, and processing and storage. We will also investigate the bioavailability and chemopreventive properties of flavonoids, particularly anthocyanins, from berry fruit in a mouse model by examining their actions to reduce oxidative stress, modulate cell signaling pathways, decrease inflammation, and promote phase II detoxification. A rat model as well as microsomes from various rat tissues will be utilized to determine the effect of age on quercetin bioavailability and metabolism due to changes in phase II enzyme activity. We will explore the possible fetal origins of chronic disease by feeding obesigenic diets to rat dams during pregnancy and lactation and examine the change in obese phenotypes in their pups and test whether dietary flavonoids, particularly isoflavones, will decrease this phenotype. Using healthy older adults, we will determine the bioavailability and distribution of cranberry anthocyanins to blood, urine, and feces. Employing volunteers with coronary heart disease, we will test the effect of almond consumption on biomarkers of oxidative stress, inflammation, and vascular reactivity.
3. Progress Report
The polyphenol content of almond skins vary with cultivar, geographical region, and harvest year. The content of 18 polyphenols and FRAP antioxidant activity of Nonpareil, Carmel, Butte, Sonora, Fritz, Mission, and Monterey almond cultivars harvested over 3 years and in 3 regions of California were examined. The 3-year mean polyphenol content of the cultivars ranged over 2-fold, with Sonora and Fritz being the highest and lowest, respectively. Catechin, epicatechin, naringenin-7-O-glucoside, kaempferol-3-O-rutinoside, dihydroxykaempferol, isorhamnetin-3-O- rutinoside, naringenin, and isorhamnetin-3-O-glucoside were the major polyphenols. Though the polyphenol content varied across harvest years, total phenols and Ferric Reducing Antioxidant Power (FRAP) values were comparable. Almonds from southern California had less polyphenols and total phenols but similar FRAP than those from the north. Cultivar, but not season or region, had a differential impact on the synthetic capacity for specific polyphenols. Multivariate analysis of these data distinguished cultivars, growth region, and harvest year with 80% confidence. Roasting, pasteurization and storage of California almonds affect their polyphenol content and antioxidant activity. In addition to identifying and quantifying almond flavonoids in various cultivars, harvest years, and California geography, we have characterized the effect of processing on these antioxidant phytochemicals. We found that: [a] roasting decreased total phenols and FRAP values, but did not change polyphenol content; [b] pasteurization methods did not change the antioxidant activity or polyphenol content of almond skins; [c] storage of almonds at 4ºC for up to 15 mo nearly doubled polyphenol content and antioxidant activity; and [d] the increase in polyphenol content in almonds due to accelerated aging may be related to the interaction of the skin with the seed nutrients. Putative health benefits attributed to cranberry consumption include a reduced risk of urinary tract infections, stomach ulcers, and cardiovascular disease. However, data on the bioavailability and metabolism of cranberry bioactives are required to better understand their impact on pertinent risk factors for chronic disease and inform the design of clinical trials. We conducted a single-dose, pharmacokinetic study to characterize the bioavailability of flavonoids and phenolics acids from cranberry juice cocktail in healthy older adults. After a run-in period following a low polyphenol diet, fasted subjects consumed 8 oz of a low-calorie, sugar-free cranberry juice cocktail. We found marked variation in the maximal plasma concentration and the time to reach this value of sinapic acid, homovanillic acid, protocatechuic acid, myricetin, quercetin, and kaempferol. These data suggest that different phenolic constituents in cranberries are absorbed and metabolized at different locations in the gastrointestinal tract. For publication relating to this project, see parent project #1950-51000-073-00D.
1. Food constituents other than antioxidants affect the results of "Total Antioxidant Capacity" assays Assays of Total Antioxidant Capacity (TAC) have been employed to rank or standardize foods and beverages for research and marketing purposes. However, the manner in which their ingredients impact TAC values has been little studied. ARS-funded researchers from Tufts University in Boston used four different TAC assays to test grape and pomegranate juices and found their different antioxidant constituents as well as sugars and organic acids and interactions between these components affected the assay results. Testing different concentrations of the same juice for TAC also resulted in different outcomes. Thus, without a careful understanding of these complex relationships within these assays, simple rankings of the TAC value of foods and beverages may be misleading, especially with regard to their potential impact on health.
2. Values from "Total Antioxidant Capacity" assays are subject to variation from dilution factors. Flavonoids are antioxidants found in most plant foods. Consuming more flavonoids has been associated with a reduced risk of some forms of cancer and heart disease. However, little is known about whether aging influences the metabolism and potential health benefits of flavonoids. Using young, middle-aged, and old rats, ARS-funded researchers from Tufts University in Boston found that age affected the rate and type of metabolism of flavonoids in the gastrointestinal tract and liver. As the metabolism of flavonoids is important to determining their bioactivity, these findings suggest that different amounts of these nutrients might need to be consumed by people of different ages to achieve a health benefit.