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At least 937 records · Page 52Linked to original sources
PubMed2000

Isolation of black tea pigments using high-speed countercurrent chromatography and studies on properties of black tea polymers.

Isolation of theaflavins and epitheaflavic acids from black tea using high-speed countercurrent chromatography (HSCCC) on a preparative scale is demonstrated. HSCCC also enabled the isolation of a polymeric fraction from black tea. According to Roberts' classification, the polymeric fraction mainly consisted of SII thearubigins (TR). HPLC analysis showed that the isolated material is free of any known chromatographically resolved tea constituents and eluted from reversed-phase packings as a convex "hump" (a broad signal). The antioxidant activity of the TR fraction was 3.6 mmol of Trolox equivalents per gram. The total phenolic content of this fraction was determined to be 34.7 g/100 g (as gallic acid equivalents).

Antioxidants↗
PubMed2001

Isolation of antioxidant compounds from orange juice by using countercurrent supercritical fluid extraction (CC-SFE).

Antioxidants from orange juice are isolated by the use of countercurrent supercritical fluid extraction (CC-SFE) and characterized by reversed-phase liquid chromatography (RPLC) coupled to mass spectrometry (MS) and diode-array detection (DAD). A pilot-scale SFE plant equipped with a packed column has been employed for countercurrent extraction and fractionation of raw orange juice with carbon dioxide. Several experiments have been performed in order to study the effect of the countercurrent conditions on the content of antioxidative compounds. In this study, the main variable that has been considered is the solvent-to-feed ratio (S/F) because it plays an essential role in the extraction efficiency. The values tested covered a wide range of sample and solvent (CO(2)) flow rates. In each experimental run, two different extracted fractions and the residual nonextracted juice were obtained and characterized. Different flavonoids have been identified in the fractions obtained after CC-SFE. The possibility of using this process for antioxidant compounds enrichment is discussed.

Antioxidants↗
PubMed2004

Fractionation of grape anthocyanin classes using multilayer coil countercurrent chromatography with step gradient elution.

Grape anthocyanins from rosé wine pomace and grape skins were fractionated by multilayer coil countercurrent chromatography (MLCCC). Tert-butyl methyl ether/n-butanol/acetonitrile/water acidified with trifluoroacetic acid (2/2/x/5) was chosen as the solvent system because of its demonstrated efficiency in separating anthocyanins. A method combining MLCCC and step gradient elution has been developed. This method enabled the fractionation of anthocyanins as series of glucosides, and the corresponding acetylated, coumaroylated, and caffeoylated derivatives. The different anthocyanins were identified on the basis of their UV spectra, their elution time on reversed-phase HPLC as well as by mass spectrometry. A polar-colored fraction free of anthocyanin monomers and corresponding to the material remaining in the stationary phase after the completion of the gradient was recovered.

Anthocyanins↗
PubMed2005

Characterization of pigments from different high speed countercurrent chromatography wine fractions.

A red wine, made from Cabernet Sauvignon (60%) and Tannat (40%) cultivars, was fractionated by high speed countercurrent chromatography (HSCCC). The biphasic solvent system consisting of tert-butyl methyl ether/n-butanol/acetonitrile/water (2/2/1/5, acidified with 0.1% trifluoroacetic acid) was chosen for its demonstrated efficiency in separating anthocyanins. The different native and derived anthocyanins were identified on the basis of their UV-visible spectra, their elution time on reversed-phase high-performance liquid chromatography (HPLC), and their mass spectra, before and after thiolysis. The HSCCC method allowed the separation of different families of anthocyanin-derived pigments that were eluted in different fractions according to their structures. The hydrosoluble fraction was almost devoid of native anthocyanins. Further characterization (glucose quantification, UV-visible absorbance measurements) indicated that it contained flavanol and anthocyanin copolymers in which parts of the anthocyanin units were in colorless forms. Pigments in the hydrosoluble fraction showed increased resistance to sulfite bleaching and to the nucleophilic attack of water.

Anthocyanins↗
PubMed2004

Countercurrent supercritical fluid extraction and fractionation of high-added-value compounds from a hexane extract of olive leaves.

Countercurrent supercritical fluid extraction (CC-SFE) at a pilot scale plant was used for fractionation of high-added-value products from a raw extract of olive leaves in hexane. Compounds found in the raw extract were waxes, hydrocarbons, squalene, beta-carotene, triglycerides, alpha-tocopherol, beta-sitosterol, and alcohols. The CC-SFE extraction process was investigated according to a 2(3) full factorial experimental design using the following variables and ranges: extraction pressure, 75-200 bar; extraction temperature, 35-50 degrees C; and ethanol as modifier, 0-10%. Data were analyzed in terms of extraction yield, enrichment, recovery, and selectivity. Higher extraction yields were attained at 200 bar. For most of the compounds analyzed enrichment was attained at the same conditions, that is, 75 bar, 35 degrees C, and 10% ethanol. Hydrocarbons were usually recovered in the separators, whereas waxes and alpha-tocopherol remain in the raffinate. Selectivity data reveal that alpha-tocopherol is the most easily separable compound. The influence of the experimental factors on the recovery of all the compounds was studied by means of regression models. The best fitted model was attained for beta-sitosterol, with R2 = 99.25%.

Chemical Fractionation↗
PubMed2005

Determination of anthocyanins from camu-camu (Myrciaria dubia) by HPLC-PDA, HPLC-MS, and NMR.

Camu-camu [Myrciaria dubia (HBK) McVaugh] is a small fruit native to the Amazonian rain forest. Its anthocyanin profile has now been investigated for the first time. Fruits from two different regions of the São Paulo state, Brazil, were analyzed. The major anthocyanins were isolated by high-speed countercurrent chromatography. HPLC-PDA, HPLC-MS/MS, and 1H NMR were used to confirm the identity of the main anthocyanins of camu-camu. Cyanidin-3-glucoside was identified as the major pigment in the fruits from both regions, representing 89.5% in the fruits produced in Iguape and 88.0% in those from Mirandópolis, followed by the delphinidin-3-glucoside, ranging between 4.2 and 5.1%, respectively. Higher total anthocyanin contents were detected in the fruits from Iguape (54.0 +/- 25.9 mg/100 g) compared to those from Mirandópolis (30.3 +/- 6.8 mg/100 g), most likely because of the lower temperatures in the Iguape region.

Anthocyanins↗
PubMed2006

Nonvolatiles of commercial lime and grapefruit oils separated by high-speed countercurrent chromatography.

The nonvolatile fractions of cold-pressed peel oils of Key and Persian lime as well as grapefruit were separated by high-speed countercurrent chromatography (HS-CCC). In addition to the isolation of the main coumarins, psoralens and polymethoxyflavones, a number of minor constituents were enriched and successfully characterized by GC-MS and HPLC-UV. 5,7,8-Trimethoxycoumarin and the cyclical acetals of oxypeucedanin hydrate with citral were determined as new nonvolatile trace constituents of lime oils and confirmed by NMR spectroscopy. The citral oxypeucedaninyl acetals were found particularly in Key lime oil type A, which as a result of the juice-oil contact, is exposed to acidic conditions during industrial processing. Some of the confirmed minor constituents, such as pabulenol, isooxypeucedanin, and oxypeucedanin methanolate in lime as well as auraptenol in grapefruit, may have been generated by hydrolysis-sensitive precursors during CCC separation or their respective industrial processing techniques.

Citrus paradisi↗
PubMed2000

Separation and purification of anthocyanins by high-speed countercurrent chromatography and screening for antioxidant activity.

The all-liquid chromatographic technique of high-speed countercurrent chromatography (HSCCC) has been applied for separations of anthocyanins. The biphasic mixture of tert-butyl methyl ether/n-butanol/acetonitrile/water (2:2:1:5) acidified with trifluoroacetic acid was found to be a suitable solvent system for anthocyanin separation. In some cases, enrichment of the pigments on Amberlite XAD-7 resin prior to HSCCC has been carried out. The anthocyanin mixtures from red cabbage, black currant, black chokeberry, and roselle were successfully fractionated using HSCCC. Peak purity control was done by nuclear magnetic resonance spectroscopy as well as electrospray ionization ion trap multiple mass spectrometry. Finally, antioxidant activity of the purified pigments was determined using the Trolox equivalent antioxidant capacity test.

Anthocyanins↗
PubMed1976

Biological activity of C-terminal partial sequences of substance P.

Substance P (Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH2) and the C-terminal partial sequences down to the tripeptide were synthesized by a solid-phase method. These peptides were assayed for vasodilator, spasmogenic, and venoconstrictor properties using three preparations, viz. the hind limb blood flow of the dog, isolated guinea pig ileum, and the isolated rabbit ear vein. The tripeptide and tetrapeptide possessed weak vasodilator properties only but no activity was detected on the other less sensitive preparations. The pentapeptide produced appreciable spasmogenic and vasoactive effects. Sequences of six or more C-terminal amino acids were able to elicity activity at comparable doses to that of the parent endecapeptide; however, the activity did not increase regularly with the chain length. In each assay preparation the octapeptide was the most potent peptide. It was twice as potent as substance P on a molar basis in the guinea pig ileum but the enhancement of activity beyond that of substance P was less pronounced in the vascular preparations.

Amino Acid Sequence↗
PubMed1975

Synthesis and properties of new bradykinin potentiating peptides.

In a study of the relationship between structure and activity of bradykinin potentiating peptides (BPP), six analogs and homologs of peptides occurring in the venoms of Bothrops jararaca and Agkistrodon halys blomhoffii were synthesized and assayed in the isolated guinea pig ileum and rat uterus. None of the peptides had bradykinin-like activity and their bradykinin potentiating activity was much greater in the guinea pig ileum than in the uterus. The following observations were made with the guinea pig ileum. The introduction of Gln as the eigth residue in potentiator B (pGlu-Gly-Leu-Pro-Pro-Arg-Pro-Lys-Ile-Pro-Pro) and potentiator C (pGlu-Gly-Leu-Pro-Pro-Gly-Pro-Pro-Ile-Pro-Pro) produced a small increase in their bradykinin potentiating activity. Removal of the two N-terminal residues of [Gln8]-potentiator B and [Gln8]-potentiator C led to alterations in activity that paralleled those described earlier for the parent compounds (potentiators B and C). The peptide with the sequence pGlu-Trp-Pro-Ary-Pro-Lys-Trp-Ala-Pro was seven times as active as BPP5a, while the most potent natural BPP, a nonapeptide from B. jararaca venom, is reported to be only four times as active as BPP5a. An analog of the above-mentioned nonapeptide containing Pro8 instead of Ala8 was only as active as BPPa. For all of the peptides, as well as for potentiatrs B and C and BPP5a, the concentration vs. potentiating activity curves had similar shapes, with a plateau at twofold potentiation and a maximum potentiation of 10- to 11-fold. A direct action on the bradykinin receptors may be responsible for the effects observed at lower BPP concentration while the effects at higher concentrations may be due to kininase inhibition. The potentiating activities of potentiator B and its Gln8 analog persisted after the peptides were removed from the medium. This "sensitizing activity" was not observed with any of the other peptides.

Amino Acid Sequence↗
PubMed2001

Isolation of symlandine from the roots of common comfrey (Symphytum officinale) using countercurrent chromatography.

Three pyrrolizidine alkaloids, symlandine, symphytine, and echimidine (1-3), were isolated from the roots of Symphytum officinale using a one-step countercurrent chromatography procedure. The structures of 1-3 were confirmed by several spectroscopic techniques including 2D NMR methods. This is the first description of the separation of symlandine (1) from its stereoisomer, symphytine (2).

Countercurrent Distribution↗