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G R Beecher

Publications and source records attributed to G R Beecher.

At least 37 records · Page 2Linked to original sources
PubMed1995

Isolation, structural elucidation, and partial synthesis of lutein dehydration products in extracts from human plasma.

All-E-(3R,6'R)-3-hydroxy-3',4'-didehydro-beta,gamma-carotene (anhydrolutein I) and all-E-(3R,6'R)-3-hydroxy-2',3'-didehydro-beta,epsilon-carotene (2',3'-anhydrolutein II) have been isolated and characterized from extracts of human plasma using semipreparative high-performance liquid chromatography (HPLC) on a C18 reversed-phase column. The identification of anhydroluteins was accomplished by comparison of the UV-Vis absorption and mass spectral data as well as HPLC-UV-Vis-mass spectrometry (MS) spiking experiments using fully characterized synthetic compounds. Partial synthesis of anhydroluteins from the reaction of lutein with 2% H2SO4 in acetone, in addition to anhydrolutein I (54%) and 2',3'-anhydrolutein II (19%), also gave (3'R)-3'-hydroxy-3,4-dehydro-beta-carotene (3',4'-anhydrolutein III, 19%). While anhydrolutein I has been shown to be usually accompanied by minute quantities of 2',3'-anhydrolutein II (ca. 7-10%) in human plasma, 3',4'-anhydrolutein III has not been detected. The presence of anhydrolutein I and II in human plasma is postulated to be due to acid catalyzed dehydration of the dietary lutein as it passes through the stomach. These anhydroluteins have also been prepared by conversion of lutein diacetate to the corresponding anhydrolutein acetates followed by alkaline hydrolysis. However, under identical acidic conditions, loss of acetic acid from lutein diacetate proceeded at a much slower rate than dehydration of lutein. The structures of the synthetic anhydroluteins, including their absolute configuration at C(3) and C(6') have been unambiguously established by 1H NMR and in part by 13C NMR, and circular dichroism.

Chromatography, High Pressure Liquid↗
PubMed1995

Lutein, lycopene, and their oxidative metabolites in chemoprevention of cancer.

Numerous epidemiological studies have demonstrated that consuming large quantities of fruits and vegetables reduces the risk for several types of human cancers. Carotenoids are abundant in fruits and vegetables and have been extensively studied as cancer preventive agents. A proposed mechanism of action for the protective effect of carotenoids against cancer is based on their antioxidant capability. Recently, we have isolated and characterized 14 new carotenoids, including seven metabolites from the extracts of human serum/plasma. This brings the total number of identified blood carotenoids to 21. Lutein and lycopene, abundant in most fruits and vegetables as well as human serum, have been shown to possess strong antioxidant capability. Among the metabolites of lutein, four results from oxidation and two from non-enzymatic dehydration. The metabolite of lycopene has been identified as 5,6-dihydroxy-5,6-dihydrolycopene, which apparently results from oxidation of lycopene to an intermediate, lycopene epoxide. This intermediate may undergo metabolic reduction to form the lycopene metabolite. Although in vivo oxidation of lutein to its metabolites has been demonstrated based on data obtained from two human studies, in vivo oxidation of lycopene to its metabolite has not yet been established. Recent preliminary studies involving healthy subjects ingesting purified lutein and zeaxanthin (a dietary dihydroxycarotenoid isomeric to lutein) are presented. We propose a possible antioxidant mechanism of action for lutein and lycopene that leads to formation of the oxidation products of these promising chemopreventive agents.

Anticarcinogenic Agents↗
PubMed1995

Effect of alcohol consumption on plasma carotenoid concentrations in premenopausal women: a controlled dietary study.

This 6-mo controlled dietary study compared the effect of 30 g alcohol/d for three menstrual cycles with three alcohol-free cycles on plasma carotenoid concentrations in 18 nonsmoking, premenopausal women. Participants were randomly allocated within a crossover design to either phase and consumed approximately 6 mg total carotenoids/d under isoenergetic conditions. Blood was drawn during the third menstrual cycle of each alcohol phase. After adjustment for the mean daily specific carotenoid and energy intakes for each alcohol phase, the paired differences in mean plasma alpha- and beta-carotene concentrations were significantly higher by 19% (P = 0.027) and 13% (P = 0.034), respectively, during the alcohol-intake phase of the study. The paired difference in mean plasma lutein/zeaxanthin concentration was significantly lower by 17% (P = 0.031) when the participants consumed alcohol than when they did not. This is the first reported study in women to document the independent effect of alcohol on plasma carotenoid concentrations without the potential interaction of smoking under controlled dietary conditions.

Adult↗
PubMed1994

Relationship between dietary intake and plasma concentrations of carotenoids in premenopausal women: application of the USDA-NCI carotenoid food-composition database.

The diet-plasma relationships for carotenoids were examined in a group of 98 nonsmoking premenopausal women who participated in the cross-sectional phase of the National Cancer Institute (NCI)-US Department of Agriculture (USDA) diet study on alcohol-hormone metabolism, 1988-90. With use of the newly developed USDA-NCI carotenoid food-composition database, the mean daily intakes of carotenoids were significantly higher when estimated from the food-frequency questionnaire (FFQ) than from the 7-d diet records. Lycopene (mean = 0.58 mmol/L), lutein plus zeaxanthin (mean = 0.46 mmol/L), and beta-carotene (mean = 0.34 mmol/L) were the major plasma carotenoids. After adjustment for body mass index, energy and alcohol intakes, and total plasma cholesterol concentration, the following significant correlation (P < 0.05) were observed between the diet record and the FFQ-estimated carotenoid intakes and their respective plasma concentrations: alpha-carotene (r = 0.58 vs 0.49), beta-carotene (r = 0.51 vs 0.49), beta-cryptoxanthin (r = 0.49 vs 0.36), lutein plus zeaxanthin (r = 0.31 vs 0.37), lycopene (r = 0.50 vs 0.26), and total carotenoids (r = 0.57 vs 0.49). These data indicate that plasma carotenoid concentrations are reflective of dietary intake, but the magnitude of the correlation varies depending on the specific carotenoid and on the dietary assessment tool.

Adult↗
PubMed1993

Carotenoid content of fruits and vegetables: an evaluation of analytic data.

The test of the association between dietary intake of specific carotenoids and disease incidence requires the availability of accurate and current food composition data for individual carotenoids. To generate a carotenoid database, an artificial intelligence system was developed to evaluate data for carotenoid content of food in five general categories, namely, number of samples, analytic method, sample handling, sampling plan, and analytic quality control. Within these categories, criteria have been created to rate analytic data for beta-carotene, alpha-carotene, lutein, lycopene, and beta-cryptoxanthin in fruits and vegetables. These carotenoids are also found in human blood. Following the evaluation of data, acceptable values for each carotenoid in the foods were combined to generate a database of 120 foods. The database includes the food description; median, minimum, and maximum values for the specific carotenoids in each food; the number of acceptable values and their references; and a confidence code, which is an indicator of the reliability of a specific carotenoid value for a food. The carotenoid database can be used to estimate the intake of specific carotenoids in order to examine the association between dietary carotenoids and disease incidence.

Carotenoids↗
PubMed1993

The development and application of a carotenoid database for fruits, vegetables, and selected multicomponent foods.

A carotenoid database for individual and multicomponent foods has been compiled that contains values for the five most common carotenoids (alpha-carotene, beta-carotene, beta-cryptoxanthin, lycopene, lutein) in 2,458 fruits, vegetables, and multicomponent foods containing fruits and vegetables. The database was used to estimate intakes of specific carotenoids for 19- to 50-year-old women (n = 1,102), using food consumption data obtained from dietary recalls in the US Department of Agriculture Continuing Survey of Food Intake by Individuals, 1986. The major contributors of alpha-carotene were carrots consumed as a single food or as an ingredient in multicomponent foods. Carrots, cantaloupe, and broccoli were the main sources of beta-carotene. Orange juices and blends, oranges, and tangerines were important contributors of beta-cryptoxanthin. Tomatoes and tomato products consumed as single foods or as ingredients in multicomponent foods provided most of the dietary lycopene. Contributors of lutein + zeaxanthin included collard, mustard, or turnip greens; spinach; and broccoli. The per capita consumption of total carotenoids (the sum of the five specific carotenoids) among these women was approximately 6 mg/day.

Adult↗
PubMed1993

The correlation between two dietary assessments of carotenoid intake and plasma carotenoid concentrations: application of a carotenoid food-composition database.

A newly available carotenoid food-composition database providing specific carotenoid values for > 2300 foods was linked to dietary data on 57 male nonsmokers to examine the association between dietary carotenoid intake and plasma carotenoid concentrations over 3 wk when free-living. Carotenoid intake was estimated from a food-frequency questionnaire (FFQ) and 7 d of food diaries with concurrent analysis of plasma carotenoid concentrations. After adjustment for energy intake, percentage of energy from alcohol, and plasma lipid concentrations, significant diet-plasma correlations for the FFQ and the food diaries (FD) included alpha-carotene (r = 0.29 and 0.43), beta-carotene (r = 0.36 FFQ only), beta-cryptoxanthin (r = 0.46 and 0.44), lutein (r = 0.44 FD only), and lycopene (r = 0.53 FD only). Dietary carotenoid intakes were associated with plasma carotenoid concentrations for all the carotenoids except for beta-carotene when food diaries were used whereas the diet-plasma correlation for the provitamin A carotenoids were consistently significant when the FFQ was used.

Adult↗
PubMed1992

Isolation and structural elucidation of the geometrical isomers of lutein and zeaxanthin in extracts from human plasma.

All-E-(3R,3'R,6'R)-lutein, all-E-(3R,3'R)-zeaxanthin, all-E-(3R,3'S,6'R)-3'-epilutein and some geometrical isomers of the former two dihydroxycarotenoids have been separated from an extract of human plasma by semipreparative high-performance liquid chromatography on a silica-based nitrile-bonded column. In the order of chromatographic elution, the isolated fractions were identified as all-E-lutein, all-E-zeaxanthin, all-E-3'-epilutein, 9Z-lutein, 9'Z-lutein, a mixture of 13Z-lutein and 13'Z-lutein, 9Z-zeaxanthin, 13Z-zeaxanthin and 15Z-zeaxanthin. The structures of all compounds, including the relative configuration at C(3') and C(6') of the luteins and the position of the stereomutated double bonds in the geometrical isomers, were unambiguously established by 1H nuclear magnetic resonance spectroscopy. The absolute configuration of the three all-E compounds was derived by circular dichroism and is also assumed to be valid for the geometrical isomers. The ultraviolet-visible absorption and mass spectra of each of the individually isolated compounds were also in agreement with the proposed structures.

Carotenoids↗
PubMed1992

Separation and identification of carotenoids and their oxidation products in the extracts of human plasma.

Eighteen carotenoids as well as vitamin A and two forms of vitamin E (gamma- and alpha-tocopherol) have been separated from extracts of human plasma by high-performance liquid chromatography (HPLC) on reversed-phase and sillca-based nitrile-bonded columns. In the order of chromatographic elution on a C18 reversed-phase column, the carotenoids were identified as (3R,3'R,6'R)-beta, epsilon-carotene-3,3'-diol [(3R,3'R,6'R)-lutein], (3R,3'R)-beta, beta-carotene-3,3'-diol [(3R,3'R)-zeaxanthin], 5,6-dihydroxy-5,6-dihydro-psi,psi-carotene, 3-hydroxy-2',3'-didehydro-beta,epsilon-caroten-3-ol, 3-hydroxy-beta-carotene,psi,psi-carotene, 7,8-dihydro-psi,psi-carotene, beta,psi-carotene, 7,8,7',8'-tetrahydro-psi,psi-carotene, beta,epsilon-carotene, beta,beta-carotene, 7,8,11,12,7',8'-hexahydro-psi,psi-carotene, and 7,8,11,12,7',8'-11',12'-octahydro-psi,psi-carotene. The polar carotenoids, which eluted in the vicinity of lutein and were unresolved on the C18 column, have been separated on a nitrile-bonded column employing isocratic HPLC conditions. In the order of elution, the carotenoids were epsilon,epsilon-carotene-3,3'-dione, 3'-hydroxy-epsilon,epsilon-caroten-3-one, 5,6-dihydroxy-5,6-dihydro-psi,psi-carotene, 3-hydroxy-beta,epsilon-caroten-3'-one, (all-E,3R,3'R,6'R)-lutein, (all-E,3R,3'R)-zeaxanthin, and (all-E,3R,3'S,6'R)-beta,epsilon-carotene-3,3'-diol (3'-epilutein) followed by several geometrical isomers of lutein and zeaxanthin.

Carotenoids↗
PubMed1992

Plasma carotenoid response to chronic intake of selected foods and beta-carotene supplements in men.

We determined serial changes in four major plasma carotenoid fractions (alpha-carotene, beta-carotene, lutein/zeaxanthin, and lycopene) in 30 men consuming defined daily doses of carotenoids from foods (broccoli, carrots, or tomato juice) or from purified beta-carotene in capsules (12 or 30 mg) for 6 wk while fed a controlled diet. Compared with baseline, beta-carotene increased in the 30- and 12-mg-capsule and carrot groups whereas alpha-carotene increased in the carrot group and lutein increased in the broccoli group. Lower lutein concentrations in recipients of beta-carotene capsules suggested an interaction between these two carotenoids. Lycopene declined in all groups except the tomato-juice group. Total carotenoid concentration changes only reflected the large increases in beta-carotene concentrations and not the smaller changes observed in other individual carotenoids. Overall, purified beta-carotene produced a greater plasma response than did similar quantities of carotenoids from foods sources. However, some foods increased plasma concentrations of certain carotenoids.

Adult↗
PubMed1990

Carotenoid analyses of selected raw and cooked foods associated with a lower risk for cancer.

We examined the carotenoid content of selected foods consistently found to be associated with a lower risk for various epithelial cancers in epidemiologic studies. Both raw and cooked samples of green, leafy vegetables and yellow or orange vegetables were quantitatively examined by high-performance liquid chromatography for individual carotenoid content. The results indicated that fresh, green, leafy vegetables were moderately high in beta carotene (0.5-14.6 mg/100 g) and very high in oxygenated carotenoids or xanthophylls, primarily lutein and its stereoisomers (2.3-63.0 mg/100g) [corrected]. The fresh, yellow or orange vegetables examined were very high in beta carotene (16.0-120.5 mg/100 g) [corrected] but had no detectable nonhydrocarbon carotenoids. Cooking differentially reduced the lutein content compared with the beta carotene content in green, leafy vegetables. These analyses suggest that consumption of carotenoids in addition to beta carotene may be associated with a lower risk for cancer.

Carotenoids↗
PubMed1989

Effect of gamma irradiation on the B vitamins of pork chops and chicken breasts.

A study was made of the effect of low-dose gamma irradiation on the content of thiamine (B1), riboflavin (B2), niacin, pyridoxine (B6) and cobalamin (B12) in pork chops, and thiamine, riboflavin and niacin in chicken breasts. Gamma irradiation from a caesium-137 source was used to irradiate the samples in a range of 0.49 to 6.65 kGy from -20 to +20 degrees C. Over the range of dose and temperature studied it was possible to derive a mathematical expression for predicting the losses. A calculation was made of the effect of the loss of thiamine, riboflavin and niacin due to irradiation on the overall loss of these vitamins in the American diet. The losses of riboflavin and niacin were of the order of a fraction of a per cent. Pork is an important source of thiamine, but the calculated loss at 1.0 kGy of this vitamin in cooked pork was only 1.5 per cent. There were initial increases with radiation doses up to 2-4 kGy in the measured concentrations of riboflavin and niacin in both pork and chicken. The increases were highly significant, and are of concern both to the study of radiation effects and the chemical method of the determination of these two vitamins.

Animals↗
PubMed1988

Separation of carotenol fatty acid esters by high-performance liquid chromatography.

Employing isocratic and gradient-elution high-performance liquid chromatography (HPLC) a number of straight-chain fatty acid esters (decanoate, laurate, myristate, palmitate) of violaxanthin, auroxanthin, lutein, zeaxanthin, isozeaxanthin, and beta-cryptoxanthin, prepared by partial synthesis, have been separated on a C18 reversed-phase column. Several chromatographic conditions were developed that separated a mixture of di-fatty acid esters (dimyristate, myristate palmitate mixed ester, dipalmitate) of violaxanthin, auroxanthin, lutein, and zeaxanthin in a single chromatographic run. Hydroxycarotenoids such as lutein, zeaxanthin, and isozeaxanthin that are not easily separated by HPLC on C18 reversed-phase columns, can be readily separated after derivatization with fatty acids and chromatography of their esters. Chromatographic conditions for optimum separation of carotenoids from various classes are discussed.

Carotenoids↗