Determination of phenolic compounds in medicinal plants from the Lamiaceae family

A procedure for the determination of Phenolic compounds in extracts from the medicinal plants of the Lamiaceae family—garden sage (Salvia officinalis L.), creeping thyme (Thymus serpyllum L.), wild marjoram (Origanum vulgare L.), and common balm (Melissa officinalis L.)—obtained under different extraction conditions was developed. The identification of the extracted compounds was performed and their qualitative and quantitative composition was established by HPLC with diode array and mass-spectrometric detection with consideration for the obtained characteristics of the standard samples of individual components. The test samples of medicinal herbs contained caffeic acid (0.19–0.62 mg/g) and rosmaric acid (4–23 mg/g); the highest rosmaric acid content (23 mg/g) was found in wild marjoram, and the lowest content (4 mg/g), in creeping thyme. The extracts of wild marjoram contained the greatest amounts of Phenolic compounds; rosmaric acid and luteolin-7-O-β-D-glucuronide were major components, whereas protocatechuic, 3-O-caffeoylquinic, and caffeic acids were minor components.     

Application of solid-phase extraction for determination of phenolic compounds in barrique wines

A fast, selective and sensitive chromatographic method has been developed for determination of gallic, protocatechuic, p-hydroxybenzoic, vanillic, caffeic, syringic, p-coumaric, benzoic, ferulic, sinapic, cinnamic, and ellagic acids and p-hydroxybenzaldehyde, vanillin, syringaldehyde, 2-furfural, 5-methylfurfural, and 5-methoxyfurfural. The compounds from untreated wine samples were pre-concentrated and cleaned using solid-phase extraction on RP-105 polymeric sorbent. The cartridge was conditioned with methanol and water. Co-extracted ballast substances were rinsed from the sorbent with 0.1 mol L^–1 hydrochloric acid–methanol, 1:4 (v/v). Retained phenolic compounds were selectively eluted with diethyl ether. A linear mobile phase gradient containing 0.3% acetic acid and methanol was used for final baseline chromatographic separation on a Hypersil BDS C18 column. Limits of detection (LOD=3s_bl) in the range 5.2 to 181.2 g L^–1, resolution (R) better than 1.7, and repeatability of 2.7–5.1% (RSD for real samples) were achieved. The method was applied for quantification of individual phenolic compounds in barrique wines.     

Antioxidant activity of phenolic and flavonoid compounds in some medicinal plants of India

In this study, total phenolics, flavonoids and vitamin C content vis-a-vis antioxidant activities were assayed in leaves and stem bark of Azadirachta indica, Butea monosperma, Cassia fistula, Mangifera indica, Syzygium cumini and Tamarindus indica using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide radical scavenging method. The DPPH radical scavenging activity positively correlated with the total phenolic content in both stem bark and leaf. Superoxide radical scavenging activity increased with increasing flavonoid contents. However, the vitamin C content could not be correlated with DPPH and superoxide radical scavenging capacity.     

Simulation of chromatography of phenolic compounds with a computational chemical method

An ab initio simulation of reversed-phase liquid chromatography for phenolic compounds was achieved based on molecular interaction energy values calculated using molecular mechanics calculations (MM2) of the CAChe program. The precision of the predicted retention factors from the molecular interaction energy values was equivalent to the predicted retention factors based on octanol-water partition coefficients (log P) calculated using the molecular orbital package (MOPAC). The prediction of retention factors of phenolic compounds in reversed-phase liquid chromatography in a given pH eluent was possible using the predicted dissociation constant (pKa) from the atomic partial charge without a chemical experiment if the organic modifier effect was known.     

Analysis of phenolic compounds in Epimedium plants using liquid chromatography coupled with electrospray ionization mass spectrometry

A new method based on HPLC coupled with electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) has been established for the analysis of phenolic compounds in Epimedium plants. The characteristic fragmentation pathways of 29 phenolic compounds were studied, and 126 compounds were identified or tentatively characterized based on their mass spectra from fourteen samples including the aerial samples and the underground parts of the seven species. Furthermore, the differences in phenolic compound profiles between different Epimedium plants and two parts of the seven species were reported for the first time. Due to their significant chemical differences, these Epimedium species should be used separately in clinical practice.     

Liquid chromatographic determination of simple phenolic compounds in waste waters from olive oil production plants.

A method was developed for the determination of simple phenolic compounds (PCs) in waste waters from olive oil production plants by liquid chromatography (LC). The sample under examination was acidified to pH 2 to precipitate proteins, acetone was added to eliminate the colloidal fraction, and hexane was used for extraction to eliminate lipidic substances. The solution obtained was filtered and injected into the LC system; the wavelength selected for the spectrophotometric detection was specific for PCs, so that carbohydrates, organic acids, and short-chain free fatty acids did not interfere. Recoveries of 9 PCs spiked to a real sample were 90-100% for concentrations ranging from 20 to 2000 mg/L for each analyte.     

Gas chromatography-atmospheric pressure chemical ionization-time of flight mass spectrometry for profiling of phenolic compounds in extra virgin olive oil

A new analytical approach based on gas chromatography coupled to atmospheric pressure chemical ionization-time of flight mass spectrometry was evaluated for its applicability for the analysis of phenolic compounds from extra-virgin olive oil. Both chromatographic and MS parameters were optimized in order to improve the sensitivity and to maximize the number of phenolic compounds detected. We performed a complete analytical validation of the method with respect to its linearity, sensitivity, precision, accuracy and possible matrix effects. The LODs ranged from 0.13 to 1.05ppm for the different tested compounds depending on their properties. The RSDs for repeatability test did not exceed 6.07% and the accuracy ranged from 95.4% to 101.5%. To demonstrate the feasibility of our method for analysis of real samples, we analyzed the extracts of three different commercial extra-virgin olive oils. We have identified unequivocally a number of phenolic compounds and obtained quantitative information for 21 of them. In general, our results show that GC-APCI-TOF MS is a flexible platform which can be considered as an interesting tool for screening, structural assignment and quantitative determination of phenolic compounds from virgin olive oil.     

Thin-layer chromatography of phenolic compounds

Summary Seventeen phenolic compounds, including phenol and the isomers of cresol, have been completely separated by thin-layer chromatography with a series of solvent/support systems.

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Zusammenfassung 17 Phenolverbindungen, darunter Phenol und die isomeren Kresole, werden dünnschichtchromatographisch mit einer Reihe von Lösungsmittel-systemen vollständig getrennt.

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Résumé On a réalisé la séparation complète de 17 composés phénoliques, y compris le phénol et les isomères du crésol, par chromatographie en couche mince, grâce à l'emploi de différents systèmes solvant/support.

     

Method for determining content of phenolic compounds in Aloe arborescens

A spectrophotometric method for quantitative determination of total content of phenolic compounds in leaves of Aloe arborescens Mill. (Liliaceae) calculated as aloenin was developed. Statistical analysis showed that the relative uncertainty of the determination method was less than 2%. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 578–580, November–December, 2008.     

Ultrasound-assisted extraction for the analysis of phenolic compounds in strawberries

A semiautomatic method based on application of ultrasounds has been developed to leach and hydrolyse phenolic compounds, such as naringin, rutin, naringenin, ellagic acid, quercetin and kaempferol, from strawberries. Two grams of lyophilized sample was placed into a sample cell and 5 mL of acetone containing hydrochloric acid was added. The cell was immersed in a water bath and sonicated for 30 s (duty cycle 0.8 s, output amplitude 50% of the nominal amplitude of the converter, applied power 100 W and with the probe placed 2 cm from the top surface of the extraction cell) for three times: each time 5 mL extractant displaced the previous extract. When the extraction was completed, the combined extracts were evaporated for 10 min, diluted to 10 mL with water adjusted to pH 8, and transferred to a cleanup–preconcentration manifold; here the analytes were retained in two in-series minicolumns packed with HR-P sorbent and then eluted with 4 mL methanol, and injected for individual separation–quantitation into a chromatograph–photodiode array detector assembly. Optimisation of the extraction was carried out using samples spiked with 4 mg kg^–1 of each analyte. Calibration curves using the standard addition in red strawberries typically gave linear dynamic ranges of 4–40 mg L^–1 for all analytes, except for ellagic acid (40–400 mg L^–1). The r ² values exceeded 0.98 in all cases.     

Formation of phenolic compounds in cotton sprouts

Summary The simplest component of the catechin complex, (+)-catechin, is formed in the cotyledons and rootlets from the very first days of the development of cotton seed. This component accumulates both in the light and in the dark. As the plant grows, catechins gradually disappear from the leaves of the cotton plant and flavonols remain. Catechins and gallocatechins are formed in the boll carpels and the bark of the roots and stems.Khimiya Prirodnykh Soedinenii, Vol. 1, No. 5, pp. 350–353, 1965     

Application of deep eutectic solvents for the extraction of phenolic compounds from extra-virgin olive oil

A HPLC–DAD/ESI–MS method has been developed and validated for the analysis of the most representative phenolic compounds in extra-virgin olive oil (EVOO) samples using a green extraction approach based on deep eutectic solvents (DESs) at room temperature. We examined ten DESs based on choline chloride and betaine in combination with different hydrogen bond donors comprising six alcohols, two organic acids, and one urea. Five phenolic compounds, belonging to the classes of secoiridoids and phenolic alcohols, were selected for the evaluation of extraction efficiency. A betaine-based DES with glycerol (molar ratio 1:2) was found to be the most effective for extracting phenolic compounds as compared to a conventional solvent. The optimization of the extraction method involved the study of the quantity of water to be added to the DES and evaluation of the sample-to-solvent ratio optimal condition. Thirty percent of water added to DES and sample to solvent ratio 1:1 (w/v) were selected as the best conditions. The chromatographic method was validated by studying LOD, LOQ, intraday and interday retention time precision, and linearity range. Recovery values obtained spiking seed oil sample aliquots with standard compounds at 5 and 100 μg/g concentration were in the range between 75.2% and 98.7%.     

In-line pressurized-fluid extraction-solid-phase extraction for determining phenolic compounds in grapes

A procedure to determine 3-alkyl-2-methoxypyrazines in wines is described. It is based on the headspace solid-phase microextraction (HS-SPME) technique after a clean-up of the sample by distillation (previously acidified to pH 0.5) to remove ethanol and other volatile compounds that can interfere in the SPME. Determination is performed by means of capillary gas chromatography using a nitrogen-phosphorus detector. The method allows quantification of 3-isobutyl-2-methoxypyrazine, 3-sec-butyl-2-methoxypyrazine and 3-isopropyl-2-methoxypyrazine at their natural concentration levels and below their sensory thresholds in Cabernet Sauvignon and Merlot wines. The method was successfully applied to experimental red wines and the evolution of their pyrazine contents during the winemaking process was monitored. Pyrazine content increased during the first maceration day but did not change significantly during alcoholic and malolactic fermentation. Final contents in wines were 12-27 ng/l of 3-isobutyl-2-methoxypyrazine and 5-10 ng/l of 3-sec-butyl-2-methoxypyrazine.     

Reversed-phase thin-layer chromatography of phenolic compounds

On a chemically-bonded C₁₈ stationary phase, the possibilities were studied of affecting the retention behavior of selected phenolic compounds (dianes, biphenyl and its hydroxy derivatives, naphthalene and its hydroxy derivatives and nitrophenols) by adding tensides to the mobile phase of water with methanol. The data obtained have been Interpreted from the point of view of interactions in the given separation system.     

Antioxidant phenolic compounds of Dracaena cambodiana

The antioxidant activities of the petroleum ether, ethyl acetate, n-BuOH and water extract fractions from Dracaena cambodiana Pierre ex Gagnep were evaluated in this study. The ethyl acetate fraction contained the highest amount of total phenolics and total flavonoids, and showed the greatest DPPH˙, ABTS+ and Superoxide anion radical-scavenging capacities. The DPPH˙, ABTS+ and Superoxide anion radical-scavenging capacities of nine compounds isolated from the ethyl acetate fraction were also evaluated. The results indicated that these compounds contributed to the antioxidant activity of D. cambodiana. Therefore, D. cambodiana and these compounds might be used as natural antioxidants.     

Competitive methylation of some phenolic compounds

The competitive methylation of a mixture of 6-hydroxy-4-methylcoumarin and of 7-hydroxy-4-methylcoumarin and also of other compounds of phenolic nature has been studied. It had ben shown that in the presence of 1 mole of alkali, methylation of the more acidic hydroxyl takes place at the oxygen atom, and with 2 moles of alkali, the stronger conjugated base reacts.