Detection and quantification of glycosylated flavonoid malonates in celery, Chinese celery, and celery seed by LC-DAD-ESI/MS

A screening method using LC-DAD-ESI/MS was applied to the analysis of flavonoids in celery, Chinese celery, and celery seeds (Apium graveolens L. and varieties). Fifteen flavonoid glycosides were detected in the three celery materials. They were identified as luteolin 7-O-apiosylglucoside, luteolin 7-O-glucoside, apigenin 7-O-apiosylglucoside, chrysoeriol 7-O-apiosylglucoside, chrysoeriol 7-O-glucoside, and more than 10 malonyl derivatives of these glycosides. The identification of the malonyl derivatives was confirmed by their conversion into glycosides upon heating and by comparison of some of the malonates with malonates that had previously been identified in red bell pepper and parsley. The concentrations of the glycosides and the malonyl glycosides in the three materials were estimated by comparison to aglycone standards. This is the first report of the presence of these glycosylated flavonoid malonates in celery.     

Systematic studies of sulfation and glucuronidation of 12 flavonoids in the mouse liver S9 fraction reveal both unique and shared positional preferences

Sulfation and glucuronidation are the principal metabolic pathways of flavonoids, and extensive phase II metabolism is the main reason for their poor bioavailabilities. The purpose of this study was to compare the similarities and differences in the positional preference of glucuronidation versus sulfation in the mouse liver S9 fraction. The conjugating rates of seven monohydroxyflavones (HFs) (i.e., 2'-, 3'-, 4'-, 3-, 5-, 6-, and 7-HF), and five dihydroxyflavones (diHFs) (i.e., 6,7-, 4',7-, 3,7-, 5,7-, and 3,4'-diHF) were determined in three separate enzymatic reaction systems: (A) sulfation only, (B) glucuronidation only, or (C) simultaneous sulfation and glucuronidation (i.e., Sult-Ugt coreaction). In general, glucuronidation rates were much faster than sulfation rates. Among the HFs, 7-HF was the best substrate for both conjugation reactions, whereas 3-HF was rapidly glucuronidated but was not sulfated. As a result, the rank order of sulfation was very different from that of glucuronidation. Among the diHFs, regiospecific glucuronidation was limited to 7-OH and 3-OH positions, whereas regiospecific sulfation was limited to 7-OH and 4'-OH positions. Other positions (i.e., 6-OH and 5-OH) in diHFs were not conjugated. The positional preferences were essentially maintained in a Sult-Ugt coreaction system, although sulfation was surprisingly enhanced. Lastly, sulfation and glucuronidation displayed different regiospecific- and substrate-dependent characteristics. In conclusion, glucuronidation and sulfation shared the same preference for 7-OH position (of flavonoids) but displayed unique preference in other positions in that glucuronidation preferred the 3-OH position whereas sulfation preferred the 4'-OH position.     

Optimization of lipase-catalyzed synthesis of acetylated tyrosol by response surface methodology

The ability of a noncommercial immobilized lipase from Staphylococcus xylosus (SXLi) to catalyze the transesterification of tyrosol and ethyl acetate was investigated. Response surface methodology was used to evaluate the effects of the temperature (40-60 degrees C), the enzyme amount (50-500 UI), and the ethyl acetate/hexane volume ratio (0.2-1) on the tyrosol acetylation conversion yield. Two independent replicates were carried out under the optimal conditions predicted by the model (reaction temperature 54 degrees C, enzyme amount 500 UI, and volume ratio ethyl acetate/hexane 0.2). The maximum conversion yield reached 95.36 +/- 3.6%, which agreed with the expected value (96.8 +/- 3.7%). The ester obtained was characterized by spectroscopic methods. Chemical acetylation of tyrosol was performed, and the products were separated using HPLC. Among the eluted products from HPLC, mono- and diacetylated derivatives were identified by positive mass spectrometry. Tyrosol and its monoacetylated derivative exert similar antiradicalar activity on 2,2-diphenyl-1-picrylhydrazyle.     

Total peroxyl radical-scavenging capacity of the chemical components from the stems of Acer tegmentosum maxim

Acer tegmentosum is a type of deciduous tree that grows in Korea. It has been used in traditional medicine for the treatment of hepatic disorders. In this study, chromatography fractionation and isolation have been successfully used to yield 15 compounds, including 10 flavonoids, 4 phenylethyl glycosides, and 1 other glycoside. Their structures were determined on the basis of their physical and spectral properties [(1)H and (13)C nuclear magnetic resonance (NMR) and mass spectrometry (MS)] and by comparison of these results to similar data in the literature. The total peroxyl radical-scavenging capacity of each isolated compound was evaluated. Among them, the most active components belong to the flavonoids. Among these, quercitrin (1), 6-hydroxy-quercetin-3-O-galactose (6), and (+)-catechin (8) showed stronger activity than the positive control Trolox.     

Deconjugation and degradation of flavonol glycosides by pig cecal microbiota characterized by Fluorescence in situ hybridization (FISH)

As the bioavailability of flavonoids is influenced by intestinal metabolism, we have investigated the microbial deconjugation and degradation of several flavonols and flavonol glycosides using the pig cecum in vitro model system developed in our group. For this model system the microbiota was directly isolated from the cecal lumen of freshly slaughtered pigs. The characterization of the cecal microbiota by fluorescence in situ hybridization (FISH) with 16S rRNA-based oligonucleotide probes confirmed the suitability of the model system for studying intestinal metabolism by the human microbiota. We have investigated the microbial degradation of quercetin-3-O-beta-d-rutinoside 1, quercetin-3-O-beta-d-glucopyranoside 2, quercetin-4'-O-beta-d-glucopyranoside 3, quercetin-3-O-beta-d-galactopyranoside 4, quercetin-3- O-beta-d-rhamnopyranoside 5, quercetin-3- O-[alpha-l-dirhamnopyranosyl-(1-->2)-(1-->6)-beta-d-glucopyranoside 6, kaempferol-3-O-[alpha-l-dirhamnopyranosyl-(1-->2)-(1-->6)-beta-d-glucopyranoside 7, apigenin 8, apigenin-8- C-glucoside (vitexin) 9, and feruloyl-O-beta-d-glucopyranoside 10 (100 microM), representing flavonoids with different aglycones, sugar moieties, and types of glycosidic bonds. The degradation rate was monitored using HPLC-DAD. The flavonol O-glycosides under study were almost completely metabolized by the intestinal microbiota within 20 min and 4 h depending on the sugar moiety and the type of glycosidic bond. The degradation rates of the quercetin monoglycosides showed a clear dependency on the hydroxyl pattern of the sugar moiety. The degradation of 2 with all hydroxyl groups of the glucose in the equatorial position was the fastest. The intestinal metabolism of di- and trisaccharides was much slower compared to the monoglycosides. The structure of the aglycone has not much influence on the intestinal metabolism; however, the type of glycosidic bond ( C- or O-glycoside) has substantial influence on the degradation rate. The liberated aglycones were completely metabolized within 8 h. Phenolic compounds such as 3,4-dihydroxyphenylacetic acid 12, 4-hydroxyphenylacetic acid 13, and phloroglucinol 18 were detected by GC-MS as main degradation products.     

Study of flavonoids of Sechium edule (Jacq) Swartz (Cucurbitaceae) different edible organs by liquid chromatography photodiode array mass spectrometry

A liquid chromatography-mass spectrometry (LC-MS)-based method was developed for the characterization of flavonoids from Sechium edule (Jacq) Swartz (Cucurbitaceae) edible organs, a plant cultivated since pre-Colombian times in Mexico where the fruit is called chayote. Chayote is used for human consumption in many countries; in addition to the fruits, stems, leaves and the tuberous part of the roots are also eaten. Eight flavonoids, including three C-glycosyl and five O-glycosyl flavones, were detected, characterized by nuclear magnetic resonance spectroscopic data, and quantified in roots, leaves, stems, and fruits of the plant by LC-photodiode array-MS. The aglycone moieties are represented by apigenin and luteolin, while the sugar units are glucose, apiose, and rhamnose. The results indicated that the highest total amount of flavonoids was in the leaves (35.0 mg/10 g of dried part), followed by roots (30.5 mg/10 g), and finally by stems (19.3 mg/10 g).     

Disposition of selected flavonoids in fruit tissues of various tomato (lycopersicon esculentum mill.) Genotypes

Flavonoids have been studied extensively because they offer great potential health benefits. In this study, enzymatic hydrolysis of glycosylated quercetin, kaempferol, and naringin was used to obtain their sugar-free aglycones. The investigation also employed a validated HPLC method to obtain the chiral disposition of the aglycone naringenin enantiomers. These analyses were conducted on exocarp, mesocarp, and seed cavity tissues of field-grown tomato (Lycopersicon esculentum Mill.) mutants (anthocyanin absent, atroviolacea, and high pigment-1) and their nearly isogenic parent (cv. Ailsa Craig) at immature green, "breaker", and red ripe maturity stages. Concentrations of all flavonoids using enzymatic hydrolysis were significantly higher than previously reported concentrations using acid hydrolysis. Presumably, this occurred due to a more specific and rapid hydrolysis of the glycoside moiety by the beta-glucosidase enzyme. The glycoside S-naringin was the predominant enantiomer in all fruit tissues, although the aglycones free R- and S-naringenin were detected in both exocarp and mesocarp. Whereas there was significantly more quercetin than kaempferol in exocarp tissue, they were present in about equal concentrations in the mesocarp. Quercetin concentrations were higher in the exocarp and mesocarp of immature green and breaker fruit of the high pigment-1 mutant than in the other genotypes, supporting the observed photoprotection and potential health benefits of the high pigment-1 tomato genotype.     

LC-ESI-MS study of the flavonoid glycoside malonates of red clover (Trifolium pratense)

High-performance liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) was applied to the analysis of the flavonoids and their glycoside malonates of the flowers and leaves of red clover (Trifolium pratense). Through LC-MS comparative studies on the plant extracts and their malonate-free extracts, approximately 20 flavonoid glycoside malonates were detected in the flower extract. Eight were identified as genistin 6' '-O-malonate (39), formononetin 7-O-beta-D-glucoside 6' '-O-malonate (40), biochanin A 7-O-beta-D-glucoside 6' '-O-malonate (41), trifoside 6' '-O-malonate (42), irilone 4'-O-beta-D-glucoside 6' '-O-malonate (43), pratensein 7-O-beta-D-glucoside 6' '-O-malonate (44), isoquercitrin 6' '-O-malonate (45), and 3-methylquercetin 7-O-beta-D-glucoside 6' '-O-malonate (46). About 15 other flavonoids and clovamides were proved to be present in this extract. The study also found that the flowers contained flavones as the major flavonoids, whereas the leaves had isoflavones as the major flavonoids. This is the first detection of the six malonates (39 and 42-46) in the extracts of red clover, and among them, 42, 43, and 46 are new compounds.     

Effect of beta-glycosidase activity of Oenococcus oeni on the glycosylated flavor precursors of Tannat wine during malolactic fermentation

Under traditional wine-making conditions, this work examines the beta-glycosidic activity of Oenococcus oeni on glycosylated aroma compounds of Tannat wines during malolactic fermentation (MLF) by comparing the changes on selected aglycones liberated. MLF diminished the content of all the glycosylated compounds. The level of the free aroma components was slightly modified by the action of the malolactic fermentation so that the cleavage of the glycosidic linkage by the beta-glycosidic activity of O. oeni did not appear to increase significatively the aglycone contents. The consequences of further chemical rearrangements of the algycones under wine conditions were explored using synthesized glycoconjugates on synthetic medium. Bacteria could also be responsible for the cleavage of aroma glycosylated compounds, being the aglycone adsorbed on polysaccharides or peptidoglycans and was released into the external medium. This hypothesis was studied through the evaluation of a stable arrangement of aroma compounds with polysaccharides produced by lactic acid bacteria. A possible retaining of free-made aroma compounds into the whole cells of O. oeni was also investigated through cell culture analysis. Through the results obtained, we assume stable linkage of aroma compounds with bacterial polysaccharides.     

Simultaneous identification of soyasaponins and isoflavones and quantification of soyasaponin Bb in soy products,using liquid chromatography/electrospray ionization-mass spectrometry

A method has been developed for simultaneous identification of soyasaponins and soy isoflavones in soy products, based on liquid chromatography/electrospray ionization-mass spectrometry (LC/ESI-MS). Soy-based nutraceutical products were analyzed by LC/ESI-MS with detection of protonated and sodiated molecular ions, as well as characteristic fragment ions for these compounds. Soy isoflavones were characterized by a strong protonated molecular ion in addition to corresponding [aglycone + H](+) ions. Monitoring the soyasaponin-specific protonated aglycone and dehydrated aglycone ions throughout the chromatogram provided a unique fingerprint for soyasaponin content in the samples. This mass spectrometric fingerprint also allowed immediate classification of the soyasaponin analytes as group A or B soyasaponins, based on the unique masses of aglycone ions observed for each class. Quantification of soyasaponin B(b) in soy-derived materials, based on the use of a purified soyasaponin B(b) standard and a glycyrrhizin internal standard, has been accomplished.     

Effect of organic and conventional cropping systems on ascorbic acid, vitamin C, flavonoids, nitrate, and oxalate in 27 varieties of spinach (Spinacia oleracea L.)

This study was undertaken to compare the levels of ascorbic acid, vitamin C, flavonoids, nitrate, and oxalate in 27 spinach varieties grown in certified organic and conventional cropping systems. Liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-(ESI)MS/MS) of methanolic extracts of spinach demonstrated 17 flavonoids, including glucuronides and acylated di- and triglycosides of methylated and methylenedioxyderivatives of 6-oxygenated flavonoids. The mean levels of ascorbic acid and flavonoids were significantly (p < 0.001) higher in the organically grown [40.48 ± 6.16 and 2.83 ± 0.03 mg/kg of fresh weight (FW)] spinach compared to the conventionally grown spinach (25.75 ± 6.12 and 2.27 ± 0.02 mg/kg of FW). Conversely, the mean levels of nitrate were significantly (p < 0.001) higher in the conventionally grown spinach compared to the organically grown spinach. No significant effects were observed in the oxalate content of spinach from either production system. The levels of nitrate correlated negatively with those of ascorbic acid, vitamin C, and total flavonoids and showed a positive correlation with the oxalate content. These results suggest that organic cropping systems result in spinach with lower levels of nitrates and higher levels of flavonoids and ascorbic acid.     

Development of a radioimmunoassay for the quantitative determination of 8-prenylnaringenin in biological matrices

Seven carboxylic acid haptens of 8-prenylnaringenin (8-PN) were synthesized, coupled to cationized bovine serum albumin, and employed to raise specific antisera in rabbits. Two linkers of different lengths (C3H6COOH and C6H12COOH) were coupled to the C7-OH group and separated into their respective enantiomers yielding the first four haptens. Racemic derivatives with C4'-OH coupled linkers C5H10COOH and C9H18COOH were synthesized carrying a methylated C7-OH. Another racemic C4'-OH hapten (CH2COOH) was prepared starting from naringenin. The haptens elicited variable antibody titers dependent on linker lengths, with short linkers giving the best results. Three antisera were characterized in detail: anti-C7-carboxy-propyloxy-2S-(-)-8-PN (anti-H-11), anti-C7-carboxy-propyloxy-2R-(+)-8-PN (anti-H-10), and anti-C4'-carboxy-methoxy-rac-8-PN (anti-H-25). anti-H-10 and anti-H-11 showed about 9% enantiomeric cross-reactivity, and anti-H-11 did not discriminate between isoxanthohumol (IX) and 8-PN (84% cross-reactivity). For anti-H-10, cross-reactivities in the range of 2-5% were found for xanthohumol, IX, and 6-prenylnaringenin. Respective numbers for anti-H-25 were 0.02, 0.1, and 0.2%. Tritiated 8-PN was synthesized yielding a 3H-tracer of high specific radioactivity (2.22 GBq/mg). A radioimmunoassay using anti-H-25 and 3H-8-PN was established and used for the quantitative determination of 8-PN in various beer brands and in the urine of six men after the consumption of three different brands of beer. Furthermore, the dose-dependent excretion of 8-PN was tested after the consumption of a higher volume of a single beer brand with and without spiking with 8-PN and a small oral dose of authentic 8-PN, respectively. Conflicting results led to a pilot test on the in vivo conversion (demethylation) of IX into 8-PN in two men. Conversion rates of 1.9 and 4.4% were estimated. Thus, the total 8-PN dose in beer brands spiced with natural hop or hop products seems to be the sum of the 8-PN amount in a consumed volume and the amount arising from the conversion of IX.     

Chromatographic profiles and identification of new phenolic components of Ginkgo biloba leaves and selected products

Ginkgo biloba leaves and their extracts are one of the most widely used herbal products and/or dietary supplements in the world. A systematic study of the phenolic compounds is necessary to establish quality parameters. A modified LC-DAD-ESI/MS method was used to obtain chromatographic profiles for the flavonoids and terpene lactones of Ginkgo biloba leaves. The method was used to identify 45 glycosylated flavonols and flavones, 3 flavonol aglycones, catechin, 10 biflavones, a dihydroxybenzoic acid, and 4 terpene lactones in an aqueous methanol extract of the leaves. The extracted G. biloba leaf products contained the same flavonoids as the raw leaves except for the lack of biflavones. The detected glycosylated flavonol contents were equal to or more than 0.0008% of the dry plant material. This is the first report of the presence of more than 20 of these flavonoids in G. biloba.     

超声波微波协同提取沙棘叶黄酮及其组成和活性研究

沙棘叶中富含黄酮类化合物等多种活性成分,为提高其提取率和利用率,本研究采用常规溶剂萃取、超声辅助、微波辅助、超声波微波协同提取4种方法对沙棘叶黄酮进行提取,测定沙棘叶黄酮得率并观察沙棘叶的微观组织结构,比较筛选沙棘叶黄酮的最佳提取方法。并采用响应面法对最佳提取方法进行工艺优化,同时测定沙棘叶黄酮组成和体外抗氧化活性。结果表明,超声波微波协同提取法是提取沙棘叶黄酮的最佳方法,黄酮得率较常规溶剂萃取法提高了42.54%(P<0.05),沙棘叶细胞损伤最严重。超声波微波协同提取沙棘叶黄酮的最佳工艺为乙醇体积分数61%、提取时间18 min、微波功率446 W,此时黄酮得率为42.09 mg·g^-1。沙棘叶黄酮提取液中共鉴定出6种黄酮类成分,分别为儿茶素、丁香酸、山萘酚、槲皮素、异鼠李素、杨梅素,其中儿茶素含量最高,为1.474 8 mg·g^-1,其余5种的含量均在0.1~0.3 mg·g^-1之间,山萘酚最低,为0.125 2 mg·g^-1;沙棘叶黄酮提取液具有较强的还原力及较高的1,1-二苯基-2-三硝基苯肼(DPPH)、2,2'-联氮-双-3-乙基苯并噻唑啉-6-磺酸(ABTS)和羟基自由基清除率,抗氧化活性较高。本研究为沙棘叶黄酮的工业化生产提供了科学依据。     

Quercetin-4'-glucoside is more potent than quercetin-3-glucoside in protection of rat intestinal mucosa homogenates against iron ion-induced lipid peroxidation

Quercetin is a typical antioxidative flavonoid found in vegetables, which is more commonly present as its glucosides, quercetin-3-glucoside (Q3G) and quercetin-4'-glucoside (Q4'G). The main aim of this study was to estimate the antioxidant activity of Q3G and Q4'G on iron ion-driven lipid peroxidation of the gastrointestinal mucosa. Q4'G markedly suppressed the lipid peroxidation when rat gastrointestinal mucosa homogenates were incubated with Fe(NO3)3 and ascorbic acid. Its effectiveness was greater as compared to that of Q3G and comparable to that of quercetin aglycone. Furthermore, Q4'G yielded higher amounts of quercetin aglycone than Q3G on incubation with the homogenates. However, Q4'G showed a lower chelating activity in comparison to Q3G. These results indicate that Q4'G, even though it has a low chelating activity, because of its efficient conversion to antioxidative aglycone on exposure to the mucosa, can act as a powerful antioxidant on iron ion driven lipid peroxidation in the intestinal mucosa. Thus, vegetables rich in Q4'G, such as onion, are likely to serve as favorable antioxidant sources for suppressing iron-induced oxidative stress in the intestinal tract.     

Quantification of soy isoflavones, genistein and daidzein, and conjugates in rat blood using LC/ES-MS.

Genistein is the principal soy isoflavone to which the putative beneficial effects of soy consumption have been attributed; however, the possibility of adverse biological effects (e.g., estrogenic, antithyroid) has also been raised. This paper describes development and validation of a simple and sensitive analytical method for the determination of genistein in the blood of rats receiving dietary genistein (<0.5-1250 microg of genistein aglycone/g of chow). The method uses serum/plasma deproteination, liquid-liquid extraction, deuterated genistein and daidzein internal standards, isocratic LC separation, and electrospray mass spectrometric quantification using selected ion monitoring. Extraction efficiency is approximately 85%, the detection limits for genistein and daidzein from 50 microL of rat blood are approximately 5 nM, and the limit of quantification is approximately 15 nM. Interassay precision (relative standard deviation 4.5-4.6%) and intraassay precision (3.3-6.7%) were determined from replicate analysis of a spiked control and an incurred serum sample. The distribution of conjugated and unconjugated forms of genistein in the blood of rats was determined using selective enzyme hydrolysis. The glucuronide was the predominant metabolite (>90%), and only small amounts of the sulfate conjugate and the aglycone were observed at all dose levels. No evidence for additional metabolites was obtained. The 7- and 4'-glucuronide conjugates of genistein were identified using electrospray mass spectrometry and (1)H NMR. Total blood genistein ranged from <15 nM in animals fed soy-free control diet to as high as 8.9 microM in male rats fed 1250 microg of genistein/g of chow and encompasses blood isoflavone levels observed in humans consuming a typical Asian diet and nutritional supplements (0.1-1 microM) and infants consuming soy formulas (2-7 microM).     

Enzymatic preparation of kaempferol from green tea seed and its antioxidant activity

Among the flavonols in green tea, kaempferol has many biological activities but kaempferol of plant origin is too expensive to be used in commercial products. Recently, we confirmed that green tea seed (GTS) contained a reasonable amount of kaempferol glycoside. After conducting structure analysis, two kaempferol glycosides were identified, kaempferol-3-O-[2-O-beta-D-galactopyranosyl-6-O-alpha-L-rhamnopyranosyl]-beta-D-glucopyranoside (compound 1) and kaempferol-3-O-[2-O-beta-D-xylopyranosyl-6-O-alpha-L-rhamnopyranosyl]-beta-D-glucopyranoside (compound 2), respectively. Also, a commercially useful method for kaempferol preparation was suggested by enzymatic hydrolysis using these two flavonoids. After several enzyme reactions were performed for the complete bioconversion of compounds 1 and 2 to kaempferol, we found that the optimum enzyme combination was reaction with beta-galactosidase and hesperidinase. Finally, we produced pure kaempferol with over 95% purity. We also compared the antioxidant effect of these two GTS flavonoids and its aglycone, kaempferol. Kaempferol is a more efficient scavenger of 1,1-diphenyl-2-picrylhydrazyl radicals and a better inhibitor of xanthine/xanthine oxidase than the two glycosides.     

Efficient 1H nuclear magnetic resonance method for improved quality control analyses of Ginkgo constituents

We developed an analytical method using 1H nuclear magnetic resonance (NMR) spectrometry to resolve analytical problems with Ginkgo. After a simple hydrolysis step, an NMR analysis of the terpene trilactone H-12 signals and the flavonol aglycone H-2' (or H-2'/6' for kaempferol) signals was performed. By comparing the solvent effects on the resolution of these signals, methanol-d4-benzene-d6 (65:35) was selected as the optimal 1H NMR solvent. The amounts of terpene lactones and flavonol aglycones in various commercial Ginkgo products and Ginkgo leaves were determined. This newly developed 1H NMR method enables the simultaneous analysis of terpene trilactones and flavonols and allows simple, rapid quantification of these compounds in pharmaceutical Ginkgo preparations.     

Further knowledge on the phenolic profile of Colocasia esculenta (L.) Shott

Colocasia esculenta (L.) Shott, commonly called taro, is an ancient species selected for its edible tuber. Its huge "elephant ear" like leaves are also consumed in sauces and stews or as soups. Forty-one phenolic metabolites (11 hydroxycinnamic acid derivatives and 30 glycosylated flavonoids) were identified by high-performance liquid chromatography-diode array detection-electrospray ionization/mass spectrometry (HPLC-DAD-ESI/MS(n)) in the leaves of two C. esculenta varieties cultivated in Azores Islands. To our knowledge, 34 of the 41 phenolic compounds are being reported for the first time in this species. Phenolics quantification was achieved by an HPLC-DAD accurate and sensitive validated method. Although the qualitative profile of the two varieties is quite similar, quantitative differences were observed between them. "Giant white" and "red" varieties (local denomination) contain, respectively, ca. 14 and 21% of phenolic acids, 37 and 28% of flavones mono-C-glycosides, 42 and 43% of flavones di-C-glycosides, 3 and 4% of flavones mono-C-(O-glycosyl)glycosides, and both of them ca. 2% of flavones di-C-(O-glycosyl)glycosides and 2% of flavones-O-glycosides. Luteolin-6-C-hexoside was the compound present in higher amounts in both varieties. The established phenolic profile is an added value for the authenticity and quality control of C. esculenta and may be useful in the discrimination of its varieties.     

Determination of flavonoids and phenolics and their distribution in almonds

Limited information is available concerning the qualitative and quantitative composition of polyphenolic compounds, especially flavonoids, in almonds. We determined total phenols, flavonoids, and phenolic acids in California almond (Prunus dulcis) skins and kernels among the principal almond varieties (Butte, Carmel, Fritz, Mission, Monterey, Nonpareil, Padre, and Price) with high-performance liquid chromatography (HPLC)/electrochemical detection and UV detection. Liquid chromatography/tandem mass spectrometry under identical HPLC conditions was utilized to verify identities of the predominant flavonoids and phenolic acids. Total phenols ranged from 127 (Fritz) to 241 (Padre) mg gallic acid equivalents/100 g of fresh weight. The analyses were compiled to produce a data set of 18 flavonoids and three phenolic acids. The predominant flavonoids were isorhamnetin-3-O-rutinoside and isorhamnetin-3-O-glucoside (in combination), catechin, kaempferol-3-O-rutinoside, epicatechin, quercetin-3-O-galactoside, and isorhamnetin-3-O-galactoside at 16.81, 1.93, 1.17, 0.85, 0.83, and 0.50 mg/100 g of fresh weight almonds, respectively. Using the existing approach of calculating only the aglycone form of flavonoids for use in the U.S. Department of Agriculture nutrient database, whole almonds would provide the most prevalent aglycones of isorhamnetin at 11.70 (3.32), kaempferol at 0.60 (0.17), catechin at 1.93 (0.55), quercetin at 0.72 (0.20), and epicatechin at 0.85 (0.24) mg/100 g of fresh weight (mg/oz serving), respectively. These data can lead to a better understanding of the mechanisms of action underlying the relationship between almond consumption and health-related outcomes and provide values for whole and blanched almonds suitable for inclusion in nutrient databases.