Search

Specific features of chromatographic determination of xanthophyll esters are studied using an example of marigold flower lutein diesters under reversed-phase HPLC conditions. The developed two-column method made it possible to establish that, in samples with a low solubility of carotenoids in the used solvent and on a chromatography column in using a mobile phase with a low solubility of carotenoids, the precipitation of diesters is possible, which detrimentally affects the accuracy of the chromatographic determination. A critical factor in this case isì temperature: the storage of samples (solutions) in a refrigerator is not always advisable, because freezing of the main components is possible. It was shown that the use of a mobile phase containing from 0 to 10 vol % acetonitrile in acetone at a temperature not lower than 20°C is acceptable for the separation of all-trans-lutein diesters from cis-derivatives of lutein and zeaxanthin derivatives on 'monomeric' C18-phases., Author(s): V. I. Deineka [sup.1] , T. G. Burzhinskaya [sup.1] , I. P. Blinova [sup.1] , L. A. Deineka [sup.1] Author Affiliations: (1) grid.445984.0, 0000 0001 2224 0652, Institute of [...]

It was found experimentally that the replacement of acetonitrile with ethanol upon the acidification of the mobile phase with phosphoric acid is an effective version for replacing acetonitrile. At that, the order of elution of glycosides of the same type of the five main anthocyanidins (delphinidin, cyanidin, petunidin, peonidin, and malvidin) does not change in eluents convenient for analysis, and the range of retention times for a complete set of such anthocyanins becomes noticeably narrower in going from acetonitrile to ethanol. To determine the effect of aglycone structure on the retention of derivatives of the same anthocyanidin (cyanidin), a mixture of six glycosides was used: one monoglycoside (3-glucoside), two 3-diglycosides (sophoroside and sambubioside), and two 3-triglycosides (2'-glucosylrutinoside and 2'-xylosylrutinoside). This mixture is a real set of anthocyanins, requiring the careful selection of the mobile phase for separating all components. In this work, based on an analysis of separation maps, the composition of a mobile phase based on ethanol is determined that ensures the achievement of the effective separation of these anthocyanins., Author(s): V. I. Deineka [sup.1] , E. Yu. Oleinits [sup.1] , I. P. Blinova [sup.1] , L. A. Deineka [sup.1] Author Affiliations: (1) grid.445984.0, 0000 0001 2224 0652, Belgorod State [...]

The chromatographic behavior (change in the logarithm of the retention factor with a change in the composition of the mobile phase) of dicaffeoylquinic (DCQ) acids is determined by the chromatographic behavior of monocaffeoylquinic acids. The most efficient combination is the conventional C18 stationary phase (Kromasil) and environmentally friendly mobile phases, in which acetonitrile is replaced by 2-propanol, with the mobile phase acidified with 0.25 vol % of phosphoric acid to stabilize the charge form of acids. The retention of dicaffeoylquinic acids can be explained by the simultaneous adsorption of caffeic acid substituents by two aromatic rings for both studied organic modifiers of the mobile phase. The replacement of the C18 phase by the phenylhexyl phase did not lead to significant changes in the selectivity of the separation of isomeric DCQ acids. At the same time, not all isomers were separated using mobile phases based on both organic modifiers: acetonitrile and 2-propanol. The developed conditions for the separation of DCQ in the gradient mode with 'green' eluents A (10 vol % of isopropanol and 0.25 vol % of phosphoric acid in water) and B (20 vol % of isopropanol and 0.25 vol % of phosphoric acid in water) were used to determine the species composition of caffeoylquinic acids in coffee, mate, and artichoke tea., Author(s): V. I. Deineka [sup.1], E. Yu. Oleinits [sup.1], A. N. Chulkov [sup.2], L. A. Deineka [sup.1] Author Affiliations: (1) grid.445984.0, 0000 0001 2224 0652, Institute of Pharmacy, Chemistry and [...]

A possibility of replacing acetonitrile for methanol in mobile phases containing an organic modifier, 10 vol. % of formic acid (pH regulator), and water in the separation of anthocyanins by reversed-phase HPLC on a C18 stationary phase (Symmetry.sup.®C18) is studied. It is found that in replacing acetonitrile for methanol, it is necessary to use two components of the mobile phase, containing only methanol and only formic acid, as on the joint presence of these substances, a prolonged retention drift is observed, presumably because of the acylation of methanol. It is found that the replacement of acetonitrile for methanol results in small changes in the selectivity of the separation of anthocyanins with identical substituents but different aglycones and with different carbohydrate substituents for one and the same aglycone. There are also no significant differences in the separation efficiency (by the number of theoretical plates) of anthocyanins, which makes it possible to reject expensive acetonitrile in favor of methanol. The developed procedure was applied to determine anthocyanins in cranberry fruits of various degrees of ripeness (by color). The specific features of the anthocyanin composition of cranberry fruits are determined and the need in controlling the composition of the sample solvent for excluding artifact peaks is shown., Author(s): V. I. Deineka [sup.1], E. Yu. Oleinits [sup.1], I. P. Blinova [sup.1], L. A. Deineka [sup.1] Author Affiliations: (1) grid.445984.0, 0000 0001 2224 0652, Belgorod State National Research University, [...]

A method for the determination of the composition of carotenoids of tomato fruits of different colors is proposed using a combination of spectrophotometry and chromatography. An explanation of the elution order of mono-cis-isomers of lycopene under the conditions of reversed-phase chromatography on traditional 'monomeric' reversed C18-phases is proposed for the first time. It was found that, for prolycopene, (7Z, 9Z, 7'Z, 9'Z)-lycopene, which is responsible for the orange color of fruits, there is an almost imperceptible transition in normal examination in the vibronic structure of the electronic absorption spectrum with the lowest energy, [lambda].sub.max(1) = 486.2 nm. The main carotenoids of tomato fruits of different colors were determined: trans-lycopene and its cis-isomers for fruits of red and pink colors, protolycopene and other carotenes preceding its biosynthesis for fruits of orange color, and the carotenoid composition of yellow tomatoes significantly differing from that of tomatoes of first two colors by a considerable accumulation of lutein. For the quantitative assessment of the concentration of carotenoids with different chromophores, a calculation system ensuring the determination of the contribution of each of the components of complex mixtures was proposed., Author(s): V. I. Deineka [sup.1], T. G. Burzhinskaya [sup.1], L. A. Deineka [sup.1], I. P. Blinova [sup.1] Author Affiliations: (1) grid.445984.0, 0000 0001 2224 0652, Institute of Pharmacy, Chemistry, and [...]

It is shown that the selectivity of the separation of 15 anthocyanins from an extract of bilberries (3-galactosides, 3-glucosides and 3-arabinosides of the five main anthocyanins: cyanidin, peonidin, delphinidin, petunidin, and malvidin) with eluents containing acetonitrile and 10 vol % HCOOH in water can be controlled by varying the concentration of acetonitrile and separation temperature. A gradient mode at a separation temperature of 25°C is proposed for the rapid separation of all components without the introduction of methanol into the mobile phase. The developed method is used to determine anthocyanins in a number of commercial fruit products of plants of the Vaccinium family: bilberries, bog bilberries, cranberries, and lingonberries. A chromatographic version for eliminating the absorbance of polymer anthocyanins in the determination of monomeric compounds in complex mixtures is proposed as an alternative to differential spectrophotometry., Author(s): V. I. Deineka [sup.1], E. Yu. Oleinits [sup.1], Ya. Yu. Kul'chenko [sup.1], I. P. Blinova [sup.1], L. A. Deineka [sup.1] Author Affiliations: (1) grid.445984.0, 0000 0001 2224 0652, Institute [...]

It was shown that the differential spectrophotometric method for the determination of monomeric anthocyanins (in a mixture with polymeric ones) is unsuitable for measurements of anthocyanins acylated by substituted cinnamic acids. This is explained by a competition between the reaction of the nucleophilic addition of a water molecule (with the release of H.sup.+) to flavylium ions with the formation of a noncolored pseudo-base (A) and the reaction of the deprotonation of flavylium ions with the formation of quinonoid structures (B), which are also colored with a certain bathochromic shift of the absorption maximum. It was proposed to estimate the applicability of the differential spectrophotometric method by comparing differences between the spectra recorded at different pH (1, 2, 3, 4, and 4.5). The method is applicable at the prevalence of route A, when the specified differences between the spectra are undistinguishable taking into account scaling. The method is inapplicable for the main route B, when spectral differences can be distinguished. In the second case, a simplified method for the determination of anthocyanins without the account of polymeric anthocyanins is justified., Author(s): L. A. Deineka [sup.1], A. N. Sidorov [sup.1], V. I. Deineka [sup.1], Ya. Yu. Kul'chenko [sup.1], I. P. Blinova [sup.1] Author Affiliations: (1) grid.445984.0, 0000 0001 2224 0652, Institute [...]

The selectivity of the separation of isomeric chlorogenic acids often found in natural samples (3, 4, and 5-caffeoylquinic acids, 3CQA, 4CQA, and 5CQA, respectively) under the conditions of reversed-phase chromatography on stationary phases of different brands, Kromasil (C18, C8, and C4), Symmetry C18, Reprosil-Pur C18-AQ, Nucleosil RPC18, and Diasfer C18, is studied. The results obtained favor the retention mechanism with predominant surface adsorption. The change in the selectivity of separation of a pair of 5CQA and 4CQA correlates with a change in the activity of residual silanol groups. At their low activity, the order of elution 3CQA < 5CQA < 4CQA does not depend on the mode (isocratic or gradient), the type of organic modifier, and the addition of an acid (formic, orthophosphoric) to the mobile phase. With an increase in the activity of silanol groups, the separation of the pair of 5CQA and 4CQA deteriorates up to the inversion of retention times. A Kromasil 100-5C18 column (250 x 4.6 mm) was chosen for a reliable separation of three acids in plant samples (instant coffee, juice, and 'Mate' tea)., Author(s): V. I. Deineka [sup.1], E. Yu. Oleinits [sup.1], I. P. Blinova [sup.1], L. A. Deineka [sup.1] Author Affiliations: (Aff1) Institute of Engineering Technologies and Natural Sciences, Belgorod State National [...]