Analysis of aliphatic and phenolic carboxylic acids by capillary supercritical fluid chromatography-Fourier-transform infrared microspectrometry

INTRODUCTION. Drugs based on rhizomes with roots of valerian (Valeriana officinalis L., family Valerianaceae) have sedative, antiarrhythmic, antispasmodic, anticonvulsant, anxiolytic effects and are widely used in psychoemotional and cognitive disorders, for the treatment of dysfunctions of the autonomic nervous system, including children, also for menopausal disorders. Biologically active compounds are contained not only in the underground, but also in the aboveground organs of the plant. This indicates the expediency of studying the qualitative chemical composition of valerian officinalis leaves to assess the possibility of use in medicine, subsequent standardization and the development of new phytopreparations based on them.AIM. Comparative phytochemical analysis of biologically active substances of leaves and rhizomes with roots of Valeriana officinalis by thin-layer chromatography.MATERIALS AND METHODS. Objects of research: leaves and rhizomes with roots of valerian harvested in various districts of the Minsk region of the Republic of Belarus in August 2023, dried by air-shade drying, ground to a coarse powder. The method of thin-layer chromatography on plates with a layer of silica gel (Sorbfil PTX-AF-A) was used to detect flavonoids and phenolic carboxylic acids. Chromatography was performed in the following mobile phases: ethyl acetate — formic acid anhydrous — water (8:1:1 and 10:2:3), acetic acid 2 and 15%; 0.020% solutions of rutin, quercetin, chlorogenic acid, and caffeic acid in 96% ethanol were used as comparison solutions. To detect sesquiterpene acids, chromatography was performed on plates with a layer of silica gel (Merck TLC Silica gel 60 F254) in the following mobile phases: glacial acetic acid — ethyl acetate — cyclohexane (2:38:60), ethyl acetate — hexane (10:90), acetone — hexane (1:2), hexane — ethyl acetate-glacial acetic acid (65:35:0.5). 0.025% solutions of valerenic acid and acetoxyvaleric acid in 96% ethanol were used as comparison solutions.RESULTS. The conditions of thin-layer chromatography have been selected to separate and identify the chemical components of leaves of Valeriana officinalis, as well as a comparative analysis with biologically active substances of rhizomes with roots of V. officinalis. It was revealed that the leaves of V. officinalis contain flavonoids, tannins and saponins, rhizomes with roots contain phenolic compounds, mainly tannins. The best separation of flavonoids and phenolic carboxylic acids was achieved in the solvent system formic acid anhydrous — water — ethyl acetate (1:1:8). It was found that extracts from the leaves of V. officinalis contain rutin and chlorogenic acid, do not contain quercetin and caffeic acid. The optimal mobile phase for the separation of sesquiterpenic acids from valerian leaf is the glacial acetic acid — ethyl acetate — cyclohexane (2:38:60) system.CONCLUSIONS. It has been established that alcoholic extracts of rhizomes with roots and leaves of valerian have a similar qualitative composition of flavonoids, phenolic carboxylic and sesquiterpenic acids. Rutin, chlorogenic, valerenic, and acetoxyvaleric acids were found in all samples. Thus, V. officinalis leaves can serve as a source of flavonoids, phenolic carboxylic and sesquiterpenic acids.

Fractionation of polyphenols in hawthorn into polymeric procyanidins, phenolic acids and flavonoids prior to high-performance liquid chromatographic analysis

Phenolic acids are one of the several classes of naturally occurring antioxidant compounds found in sweetpotatoes. Simplified, robust, and rapid methodologies were optimized to quantify total and individual phenolic acids in sweetpotato roots. Total phenolic acid content was quantified spectrophotometrically using both Folin-Denis and Folin-Ciocalteu reagents. The Folin-Ciocalteu reagent gave an overestimation of total phenolic acids due to the absorbance of interfering compounds (that is, reducing sugars and ascorbic acid). Individual phenolic acids were quantified by high-performance liquid chromatography (HPLC) using the latest in column technology. Four reversed-phase C18 analytical columns with different properties (dimensions, particle size, particle shape, pore size, and carbon load) were compared. Three different mobile phases using isocratic conditions were also evaluated. A column (4.6 x 150 mm) packed with 5-microm spherical silica particles of pore size 110 A combined with 14% carbon load provided the best and fast separation of individual phenolic acids (that is, chlorogenic acid, caffeic acid, and 3 isomers of dicaffeoylquinic acid) with a total analysis time of less than 7 min. Among the 3 mobile phases tested, a mobile phase consisting of 1% (v/v) formic acid aqueous solution: acetonitrile: 2-propanol, pH 2.5 (70:22:8, v/v/v) gave adequate separation. Among the solvents tested, aqueous mixtures (80:20, solvent:water) of methanol and ethanol provided higher phenolic acid extraction efficiency than the aqueous mixture of acetone.

The phenolic acids in wheat—III.: Insoluble derivatives of phenolic cinnamic acids as natural intermediates in lignin biosynthesis

An ultra high performance liquid chromatography with triple quadrupole mass spectrometry method for the determination of free and bound phenolic acids in tobacco plant and soil was developed. A simple solid-phase extraction, which used Polar Enhanced Polymer column as stationary phase and methanol as mobile phase, was used for the clean-up of bound phenolic acids, and a liquid-phase extraction using chloroform as solvent was used to purify free phenolic acids. With our method, 18 phenolic acids in rhizosphere soil of continuous cropping flue-cured cultivar k326 were separated and determined within 6min with recoveries of 82-107% and relative standard deviations (n=5) of 1.1-4.8%. Results showed that free phenolic acids accounted for 0-9, 92-100, and 69-100% of total phenolic acids in rhizosphere soil, cultivar k326 roots and leaves, respectively. Results also revealed that p-hydroxybenzoic acid, p-coumaric acid, vanillic acid, ferulic acid, and syringic acid were the predominant phenolic acids in rhizosphere soil of cultivar k326, and continuous cropping of cultivar k326 in the same farmland could lead to the accumulation of these phenolic acids in soil except syringic acid. The determination of phenolic acids provided detailed information for evaluating their source and characteristics in continuous cropping tobacco plant and soil.

Phenolic acids, which are widespread in plants and possess a broad spectrum of pharmacological activity, are increasingly attracting research interest. A current focus in modern pharmacy is the search for new raw materials containing phenolic acids and the development of standardization methods. Available literature confirming the presence of phenolic substances in the fruits, needles, and shoots of common juniper (Juniperus communis) allows us to consider this raw material as a source of phenolic acids. The aim of this study is to investigate the composition of phenolic substances and the quantitative content of phenolic acids, expressed as chlorogenic acid, in the fruits, needles, and shoots of common juniper (Juniperus communis). The study involved the fruits, needles, and shoots of common juniper, which were collected from cultivated shrubs in the Botanical Garden of Sechenov University, as well as from wild plants growing in the Konakovsky District of the Tver Region, in the undergrowth of a coniferous forest. The raw materials were harvested by hand in August 2022-2024. Drying was carried out in the shade. Hydroalcoholic extracts of the raw materials were obtained for further research. Phenolic compound analysis was performed by TLC, and the total content of phenolic carboxylic acids, expressed as chlorogenic acid, was quantified by UV spectrophotometry. During the TLC analysis, the presence of gallic, chlorogenic, and caffeic acids, as well as rutin and quercetin, was established in the fruits, needles, and shoots of common juniper by comparing the Rf of these substances with the Rf of standards. The content of phenolic carboxylic acids, calculated as chlorogenic acid, was determined in all of the above types of raw materials in alcohol extracts obtained by maceration with 20%, 45%, 70%, and 95% ethyl alcohol. It was found that the maximum extraction of the phenolic carboxylic fraction for this group of raw materials is observed when using 70% ethyl alcohol as an extractant.

Ternary complexes: Equilibrium studies of mixed ligand complexes of vanadyl ion with some carboxylic and phenolic acids

The development of palladium-catalyzed cross-coupling methods for the activation of C(sp2)-Br bonds facilitated access to arene-rich molecules, enabling a concomitant increase in the prevalence of this structural motif in drug molecules in recent decades. Today, there is a growing appreciation of the value of incorporating saturated C(sp3)-rich scaffolds into pharmaceutically active molecules as a means to achieve improved solubility and physiological stability, providing the impetus to develop new coupling strategies to access these challenging motifs in the most straightforward way possible. As an alternative to classical two-electron chemistry, redox chemistry can enable access to elusive transformations, most recently, by interfacing abundant first-row transition-metal catalysis with photoredox catalysis. As such, the functionalization of ubiquitous and versatile functional handles such as (aliphatic) carboxylic acids via metallaphotoredox catalysis has emerged as a valuable field of research over the past eight years.In this Account, we will outline recent progress in the development of methodologies that employ aliphatic and (hetero)aromatic carboxylic acids as adaptive functional groups. Whereas recent decarboxylative functionalization methodologies often necessitate preactivated aliphatic carboxylic acids in the form of redox-active esters or as ligands for hypervalent iodine reagents, methods that enable the direct use of the native carboxylic acid functionality are highly desired and have been accomplished through metallaphotoredox protocols. As such, we found that bench-stable aliphatic carboxylic acids can undergo diverse transformations, such as alkylation, arylation, amination, and trifluoromethylation, by leveraging metallaphotoredox catalysis with prevalent first-row transition metals such as nickel and copper. Likewise, abundant aryl carboxylic acids are now able to undergo halogenation and borylation, enabling new entry points for traditional, primarily palladium- or copper-catalyzed cross-coupling strategies. Given the breadth of the functional group tolerance of the employed reaction conditions, the late-stage functionalization of abundant carboxylic acids toward desired targets has become a standard tool in reaction design, enabling the synthesis of various diversified drug molecules. The rapid rise of this field has positively inspired pharmaceutical discovery and will be further accelerated by novel reaction development. The achievement of generality through reaction optimization campaigns allows for future breakthroughs that can render protocols more reliable and applicable for industry. This article is intended to highlight, in particular, (i) the employment of aliphatic and (hetero)aryl carboxylic acids as powerful late-stage adaptive functional handles in drug discovery and (ii) the need for the further development of still-elusive and selective transformations.We strongly believe that access to native functionalities such as carboxylic acids as adaptive handles will further inspire researchers across the world to investigate new methodologies for complex molecular targets.

The combination of supercritical fluid extraction, high resolution capillary supercritical fluid chromatography, and Fourier transform infrared microspectrometry is described for the separation and identification of polycyclic aromatic hydrocarbons in a coal tar pitch. The variable solvating power of the supercritical fluid was utilized to selectively fractionate the sample. The fluid extract was decompressed through a frit restrictor into the sample cavity of a cooled microvalve injector, where the analytes were deposited and concentrated for subsequent chromatographic analysis. Several of the analytes separated in the chromatograph were collected on a potassium bromide disc at a solvent elimination inter‐face for subsequent infrared analysis involving the use of an infra‐red microscope accessory. The spectra obtained show the power of this detection technique for distinguishing between isomers.

In attempts to uncover a relatively mild method for the oxidative degradation of humic substances, a humic and a fulvic acid were oxidized with peracetic acid at 40 °C for 8 days. The oxidation products were extracted into organic solvents, methylated, separated by column-, thin layer-, and preparative gas-chromatography, and identified by matching their mass and micro-i.r. spectra with those of authentic specimens.The major humic acid oxidation products were phenolic acids (isolated in fully methylated forms, 8.4%), benzenecarboxylic acids (as methyl esters, 16.0%), and aliphatic acids (as methyl esters, 3.4%). The fulvic acid yielded 11.5% phenolic compounds, 8.4% benzenecarboxylic acids (as methyl esters), and 2.6% aliphatic acids (as methyl esters). These data indicated a more phenolic character for the fulvic acid than for the humic acid. In addition, small amounts of 2-methyl-3,4-furandicarboxylic acid were tentatively identified as dimethyl esters among humic and fulvic acid oxidation products. As far as total yields of oxidation products were concerned, peracetic acid oxidation at 40 °C of untreated humic and fulvic acids compared favorably with permanganate oxidation of methylated humic materials at about 100 °C, but was more time consuming.The results of this and earlier oxidative degradation studies show that the oxidation of humic substances produces phenolic and benzenecarboxylic acids as major products in addition to smaller amounts of aliphatic dicarboxylic acids. Whether these products arise from more complex structures of lignin or microbial origin or whether they occur in the forms in which they were isolated but held together by hydrogen-bonding or Van der Waal's forces requires further investigation.

The genus Tripleurospermum of the Asteraceae family (Tripleurospermum, Asteraceae) is one of the numerous genera represented by 40 species. The species Tripleurospermum inodorum (L.) Sch.Bip. is found both wild in the European part of Russia and as an introduced species in Siberia and the Far East. It is an impurity in the official raw material, Chamomillae recutita flores. In the folk medicine of Eastern Siberia, T. inodorum is used as a pain-relieving, anti-inflammatory, diuretic, wound-healing, antispasmodic, anthelmintic, and insecticidal agent. There is information about the presence of bitterness, mucus, ascorbic acid, essential oil, flavonoids, and phenolic carboxylic acids. The pharmacological effects of the biologically active compounds found in the extract from the aerial parts of T. inodorum have been previously studied. It has been established that it has analgesic and anti-inflammatory effects in gastrointestinal diseases, as well as other types of activity, such as antimicrobial, anticoagulant, and antitoxic effects. This study focuses on the isolation and identification of compounds from the aerial parts of the T. inodorum species, which is native to Eastern Siberia. The raw materials were collected in the Irkutsk region during the flowering period in 2022. The isolation and identification of individual phenolic compounds were performed using preparative column chromatography on a polyamide sorbent and microcolumn HPLC on a Milichrom A-02 chromatograph. The study revealed 12 phenolic compounds, of which: 3 coumarins – coumarin, umbelliferon, esculetin; 5 flavonoids – apigenin, apigenin-7-O-glucoside, apigenin-7-O-(6"-acetyl)-glucoside, luteolin, luteolin-7-O-glucoside; 4 phenolic carboxylic acids – chlorogenic, caffeic, 3,5-dicofeylquinic, 4-O-caffeylquinic. In addition, matrixaria ether and dihydromatrixaria ether were detected. The relative content of phenolic compounds was 13,94 mg/g.

Ion-exclusion chromatographic separations of C 1–C 6 aliphatic carboxylic acids on a sulfonated styrene–divinylbenzene co-polymer resin column with 5-methylhexanoic acid as eluent

Phenolic acids are found in abundance throughout the plant kingdom. Consumption of wine or other rich sources of phenolic acids, such as the "Mediterranean diet," has been associated with a lower risk of cardiovascular disease. The underlying mechanism(s), however, has remained unclear. Here, we show that many phenolic acids, including those from the hydroxybenzoic and hydroxycinnamic acid classes, can bind and activate GPR109A (HM74a/PUMA-G), the receptor for the antidyslipidemic agent nicotinic acid. In keeping with this activity, treatment with a number of phenolic acids, including cinnamic acid, reduces lipolysis in cultured human adipocytes and in fat pats isolated from wild-type mice but not from mice deficient of GPR109A. Oral administration of cinnamic acid significantly reduces plasma levels of FFA in the wild type but not in mice deficient of GPR109A. Activation of GPR109A by phenolic acids may thus contribute to a cardiovascular benefit of these plant-derived products.

Effect of the partial molar volume of the solute in the stationary phase on retention in supercritical fluid chromatography

The stability constants of simple and mixed ligand systems of neodymium ion with bidentate ligands such as carboxylic and phenolic acids are studied in an aqueous medium by pH metric titrations at 30±0.1 °C and at an ionic strength of 0.1 M (NaClO4). Neodymium forms 1 : 1 complexes with succinic, adipic, itaconic, malonic, and 3,5-dinitrosalicylic acids and 1 : 1 and 1 : 2 complexes with phthalic, 5-sulfo-, and 4-hydroxysalicylic acids. Ternary complexes of neodymium with these acids when (i) both the ligands are carboxylic acids, (ii) one is carboxylic and the other a phenolic acid, (iii) both ligands are phenolic acids, are studied by potentiometry. The stability constants of these complexes are compared with those of binary complexes. The results have been discussed on the basis of the magnitudes of ΔlogK, KDXY, and logβXY−1⁄2[logβxx+logβyy], and also from the comparison of K2YX and KMX1 or K2XY and KMY1. The values of K2YX are directly related to the acid dissociation constant of the secondary ligand. The overall stability (βXY) is found to be depending on the binary stabilities and the basicities of the ligands.