Characterization of the multiple chemical components of Glechomae Herba using ultra high performance liquid chromatography coupled to quadrupole‐time‐of‐flight tandem mass spectrometry with diagnostic ion filtering strategy

Glechomae Herba is a traditional Chinese medicine used for the treatment of urolithiasis, cholelithiasis, and urinary tract infections in China. Identification of chemical constituents is helpful to discover the potential active ingredients. However, this significant work is stymied by complex chemical constituents. Therefore, an ultra high performance liquid chromatography coupled to quadrupole‐time‐of‐flight tandem mass spectrometry analysis with diagnostic product ions and neutral loss filtering strategy was established for chemical profiling of Glechomae Herba. The diagnostic product ions and neutral loss filtering strategy simplified spectral elucidation. A total of 120 compounds, including 10 chlorogenic acids, 10 gallic acids, 21 phenylpropionic acids, and 77 flavonoids, were reasonably identified in Glechomae Herba. Sixty‐five constituents were first discovered in Glechomae Herba. Four types of chlorogenic acids (caffeoylquinic acid, feruloylquinic acid, p‐coumaroylquinic acid, and di‐caffeoylquinic acid), three types of galloylglucoses (di‐O‐galloyl‐glucose, tri‐O‐galloyl‐glucose, and tetra‐O‐galloyl‐glucose), three types of phenylpropionic acid skeletons (p‐coumaric acid, caffeic acid, and rosmarinic acid) and five types of flavonoid aglycone skeletons (apigenin, kaempferol, luteolin, quercetin, and chrysin) were identified in Glechomae Herba. The results indicated that the developed strategy was feasible and rational technique for identifying the complex chemical constituents in Glechomae Herba.     

Identification and characterization of proanthocyanidins of 16 members of the Rhododendron genus (Ericaceae) by tandem LC–MS

The proanthocyanidins of the leaves of 16 taxa of the Rhododendron genus (Ericaceae) [Rhododendron ‘Catawbiense Grandiflorum’, Rhododendron ‘Cunningham's White’, Rhododendron smirnowii Trautv., Rhododendron calophytum Franch., Rhododendron dichroanthum ssp. scyphocalyx (Balf. f. & Forrest ) Cowan, Rhododendron micranthum Turcz., Rhododendron praevernum Hutch., Rhododendron ungernii Trautv., Rhododendron kaempferi Planch., Rhododendron degronianum ssp. heptamerum var. hondoense ( Nakai ) H. Hara, Rhododendron fortunei Lindl., Rhododendron ponticum L., Rhododendron galactinum Balf. f. ex Tagg., Rhododendron oreotrephes W. W. Sm., Rhododendron brachycarpum ssp. brachycarpum D. Don ex G. Don, and Rhododendron insigne Hemsl. & E. H. Wilson ] were investigated qualitatively by liquid chromatography–mass spectrometry in series. Twenty‐nine dimeric proanthocyanidins based on (epi)catechin and (epi)gallocatechin were detected and characterized on the basis of their unique fragmentation pattern in the negative ion mode tandem mass spectrometry spectra. All of them were extracted for the first time from these sources, and ten of them were not reported previously in nature. The position of the galloyl residue was assigned on the basis of the retro‐Diels–Alder fragmentation and the dehydrated retro‐Diels–Alder fragmentation; it resulted from the loss of gallic acid as a neutral loss in the negative ion mode. Furthermore, four caffeoylquinic acids, six p‐coumaroylquinic acids, epigallocatechin, gallocatechin, catechin, epicatechin, epigallocatechin gallate, catechin gallate, epicatechin gallate, gallocatechin gallate, two quercetin‐O‐hexosides, quercetin‐O‐galloyl‐hexoside, quercetin‐O‐pentoside, quercetin‐O‐rhamnoside, quercetin‐O‐pentoside‐O‐hexoside, quercetin‐O‐rhamnoside‐O‐hexoside, quercetin‐O‐feruloyl‐hexoside, quercetin‐O‐(p‐hydroxy)benzoyl‐hexoside, taxifolin‐O‐pentoside, myricetin‐O‐rhamnoside, two myricetin‐O‐pentosides, three myricetin‐O‐hexosides, and two myricetin‐O‐galloyl‐hexosides were detected and shown to possess characteristic tandem mass spectrometry spectra and were tentatively assigned on the basis of their retention time. Copyright © 2012 John Wiley & Sons, Ltd.     

Mössbauer Spectroscopic Investigation of FeII and FeIII 3,4,5‐Trihydroxybenzoates (Gallates) – Proposed Model Compounds for Iron‐Gall Inks

Iron gallates with iron in the oxidation states Fe²⁺ and Fe³⁺ were prepared and studied by Mössbauer spectroscopy, X‐ray diffraction, and IR spectroscopy. Fe^III 3,4,5‐trihydroxybenzoate (gallate) Fe(C₇O₅H₄) · 2H₂O, whose structure was first determined by Wunderlich, was obtained by the reaction of gallic acid and metallic iron or by oxidation of the Fe^II gallate, which was obtained by the reaction of ferrous sulfate with 3,4,5‐trihydroxybezoic acid (gallic acid) under anoxic conditions. Trials to reproduce the hydrothermal preparation method of Feller and Cheetham show that the result depends crucially on the free gas volume in the reaction vessel. If there is no free volume one obtains the same Fe^III gallate as in the other preparation methods. With a large free volume another compound was found to form whose composition and structure could not be determined. It could be specified only by Mössbauer spectroscopy. Fe^III gallate, the Fe^II gallate, and the new phase show magnetic ordering at liquid helium temperature.     

High‐speed counter‐current chromatography assisted preparative isolation of bioactive compounds from stem bark of Juglans mandshurica

High‐speed counter‐current chromatography was applied for the first time for the separation and purification of bioactive compounds contained in the stem bark of Juglans mandshurica Maxim. Silica gel column chromatography was first used to obtain three composition‐enriched target fractions from a crude J. mandshurica methanol extract. Three independent high‐speed counter‐current chromatography processes were then used to further isolate 13 bioactive compounds, namely, six galloyl glucose derivatives, three flavonones, three naphthoquinones, and ethyl gallate. The isolates were identified by ultrahigh‐performance liquid chromatography with tandem mass spectrometry, and ultraviolet and NMR spectroscopy, and compared with literature data. Their purities were determined to be >94.6% by ultrahigh performance liquid chromatography. Furthermore, based on the total phenolic content and results of a 2,2‐diphenyl‐1‐picrylhydrazyl test, the methanol extract and two of the three initial fractions were observed to be rich in phenolic compounds and exhibit good free radical scavenging abilities, while nine of the isolated compounds exhibited remarkable antioxidant activity, superior to that of butyrate hydroxy‐toluene and comparable to that of gallic acid. The results of this research confirm the effectiveness of high‐speed counter‐current chromatography for the separation of compounds contained in extremely complex samples, and provide a basis for the further utilization of J. mandshurica .     

Chronoamperometric evaluation of the antioxidant capacity of tea on a polyquercetin-modified electrode

It was established that the components of tea are oxidized on a glassy carbon electrode modified with carbon nanotubes and electropolymerized quercetin in a phosphate buffer solution (pH 7.0) as a supporting electrolyte under conditions of differential pulse voltammetry. The oxidation potentials of the individual phenolic antioxidants of tea (gallic acid, rutin, quercetin, catechin, epigallocatechin gallate, and tannin) on the modified electrode were found. A method for the chronoamperometric determination of the antioxidant capacity (AOC) of tea was developed based on the oxidation of tea antioxidants at a potential of 0.20 V. The AOC of tea was evaluated using а difference between the oxidation currents of the analyte and a supporting electrolyte after 50 s of electrolysis in terms of gallic acid. The analytical range of gallic acid was 0.25?750 μM with a detection limit of 0.063 μM. Positive correlations of the AOC with antioxidant activity in a reaction with 2,2-diphenyl-1-picrylhydrazyl and the total phenolic content were found (r = 0.700 and 0.647 at r _crit = 0.396, respectively).     

Effect of Natural Antioxidants from Marigolds (Tagetes erecta L.) on the Oxidative Stability of Soybean Oil

In recent years, synthetic antioxidants that are widely used in foods have been shown to cause detrimental health effects, and there has been growing interest in antioxidants realised from natural plant extracts. In this study, we investigate the potential effects of natural antioxidant components extracted from the forage plant marigold on the oxidative stability of soybean oil. First, HPLC-Q-TOF-MS/MS was used with 1,1-diphenyl-2-picrylhydrazyl (DPPH) to screen and identify potential antioxidant components in marigold. Four main antioxidant components were identified, including quercetagetin-7-O-glucoside (1), quercetagetin (2), quercetin (3) and patuletin (4). Among them, quercetagetin (QG) exhibited the highest content and the strongest DPPH radical scavenging activity and effectively inhibited the production of oxidation products in soybean oil during accelerated oxidation, as indicated by reductions in the peroxide value (PV) and acid value (AV). Then, the fatty acids and volatile compounds of soybean oil were determined with gas chromatography–mass spectrometry (GC-MS) and headspace solid-phase microextraction–gas chromatography–mass spectrometry (HS-SPME-GC-MS). A total of 108 volatile components, including 16 alcohols, 23 aldehydes, 25 ketones, 4 acids, 15 esters, 18 hydrocarbons, and 7 other compounds, were identified. QG significantly reduced the content and number of aldehydes and ketones, whereas the formation of acids and hydrocarbons was completely prevented. In addition, the fatty acid analysis demonstrated that QG significantly inhibited oxidation of unsaturated fatty acids. Consequently, QG was identified as a potential, new natural antioxidant that is believed to be safe, effective and economical, and it may have potential for use in plant extracts feed additives.     

Using natural deep eutectic solvents for the extraction of metabolites in Byrsonima intermedia leaves

Natural deep eutectic solvents have been used as an alternative to organic solvents for the extraction of plants metabolites, allowing for the extraction of compounds of different polarities, while being inexpensive, non‐toxic, and easy to prepare. This work presents the comparison of the chromatographic profiles by high‐performance liquid chromatography with diode‐array detection obtained from Byrsonima intermedia (Malpighiaceae) using five choline chloride‐based natural deep eutectic solvents, in addition to the most used traditional extraction solvents, methanol/water 7:3 and ethanol/water 7:3 v/v. A reference extract was used to tentatively identify compounds by high‐performance liquid chromatography with tandem mass spectrometry. The water content appeared to be important for the extraction efficiency and the mixture choline chloride/glycerol was shown to be the best candidate for efficiently extracting this matrix when compared with the traditional extraction media in addition to being far greener as shown by the environmental analysis tool. Seven phenolic compounds (digalloyl quinic acid, proanthocyanidin dimer, galloylproanthocyanidin dimer, quercetin‐O‐hexoside, galloyl quercetin hexoside, quercetin‐O‐pentoside, and galloyl quercetin pentoside) were tentatively identified in all extracts. Moreover, the influence of these solvents on the antioxidant activity of the extracts was studied and the results for choline chloride/glycerol extracts were very similar to that of the traditional extraction solvents.     

Online solid‐phase extraction with high‐performance liquid chromatography and mass spectrometry for the determination of five tannins in traditional Chinese medicine injections

A rapid analytical method based on online solid‐phase extraction with high‐performance liquid chromatography and mass spectrometry has been established and applied to the determination of tannin compounds that may cause adverse effects in traditional Chinese medicine injections. Different solid‐phase extraction sorbents have been compared and the elution buffer was optimized. The performance of the method was verified by evaluation of recovery (≥40%), repeatability (RSD ≤ 6%), linearity (r² ≥ 0.993), and limit of quantification (≤0.35 μg/mL). Five tannin compounds, gallic acid, cianidanol, gallocatechin gallate, ellagic acid, and penta‐O‐galloylglucose, were identified with concentrations ranging from 3.1–37.4 μg/mL in the analyzed traditional Chinese medicine injections.     

Formation of Dehydrohexahydroxydiphenoyl Esters by Oxidative Coupling of Galloyl Esters in an Aqueous Medium Involved in Ellagitannin Biosynthesis

Hexahydroxydiphenoyl (HHDP) and dehydrohexahydroxydiphenoyl (DHHDP) groups are the major acyl components of ellagitannins, which are polyphenols whose biosynthesis have attracted considerable attention; however, the mechanisms of the production of HHDP and DHHDP in the ellagitannin biosynthesis have not been clarified. With the aim of elucidating such a mechanism, this study investigates the CuCl₂-mediated oxidation of simple galloyl derivatives in an aqueous medium. It is shown that the oxidation of methyl gallate affords a DHHDP-type dimer, whose reduction with Na₂S₂O₄ yields an HHDP-type dimer. However, the oxidation of the HHDP-type product over CuCl₂ does not afford the parent DHHDP ester. The oxidation of 1,4-butanediol digallate under the same conditions produces a DHHDP-type product via the intramolecular coupling of galloyl groups. These results strongly suggest that the DHHDP group is the initial product of the oxidative coupling of two galloyl groups in the ellagitannin biosynthesis, and subsequent reductive metabolism affords HHDP esters.     

Systematic characterization and simultaneous quantification of the multiple components of Rhododendron dauricum based on high‐performance liquid chromatography with quadrupole time‐of‐flight tandem mass spectrometry

Rhododendron dauricum L. has been used as a traditional Chinese medicine to treat cough and asthma and relieve phlegm and bronchitis. In this study, a reliable method based on high‐performance liquid chromatography with diode array detection and quadrupole time‐of‐flight tandem mass spectrometry was established to systematically identify and quantify the components in this herb for the first time. A total of 33 compounds were identified, including 24 flavonoids, six phenolic acids, two coumarins and one terpene. Among them, poriolin ( 17 ), farrerol‐7‐O‐β‐d‐ glucopyranoside ( 20 ), and syzalterin ( 30 ) were isolated from this plant for the first time, and quercetin‐3‐β‐d‐ (6‐p‐hydroxy benzoyl) galactoside ( 19 ), quercetin‐3‐β‐d‐ (6‐p‐coumaroyl) galactoside ( 21 ), and myrciacetin ( 23 ) were identified from this genus for the first time. Fragmentation pathways of flavonoids also have been investigated by electrospray ionization mass spectrometry. Moreover, seven bioactive constituents, namely, gallic acid ( 1 ) , scopoletin (6 ), dihydroquercetin ( 7 ), quercetin ( 22 ), kaempferol ( 25 ), 8‐desmethyl farrerol ( 27 ), and farrerol ( 28 ), were simultaneously quantified. The developed method has been validated and applied to analyze ten samples of R. dauricum from Hebei Province successfully. The contents of the seven compounds have been detected and compared.     

The Synthesis of trans‐Flavan‐3‐ol Gallates by Regioselective Oxidative Etherification and Their Cytotoxicity Mediated by 67 LR

We report on a chiral pool approach for the synthesis of trans‐flavan‐3‐ol gallates from epichlorohydrin. The trans‐flavan‐3‐ol gallates were prepared by the cycloetherification of the phenol at the C2 benzylic position of 2‐acylozyl‐1,3‐diarylpropane during regioselective C?H oxidation. The 1,3‐diarylpropanes were prepared starting from epichlorohydrin by epoxide opening with A and B ring precursors, followed by acylation of the resultant alcohol with galloyl chloride. The availability of both the enantiomers of epichlorohydrin allowed the preparation of the corresponding enantiomer using the same procedure. The cytotoxicity of the compounds against U266 cells was tested, in which 5‐deoxy‐7,3′‐O‐dimethyl gallocatechin gallate exhibited cytotoxicity that was more than ten times stronger than natural (?)‐EGCG. In addition, the absolute configuration of the derivatives did not critically affect the biological activity.     

Separation of three polar compounds from Rheum tanguticum by high‐speed countercurrent chromatography with an ethyl acetate/glacial acetic acid/water system

The separation of polar compounds by high‐speed countercurrent chromatography is still regarded as a challenge. In this study, an efficient strategy for the separation of three polar compounds from Rheum tanguticum has been successfully conducted by using high‐speed countercurrent chromatography. X‐5 macroporous resin chromatography was used for the fast enrichment of the target compounds. Then, the target fraction was directly introduced into high‐speed countercurrent chromatography for separation using ethyl acetate/glacial acetic acid/water (100:1:100, v/v/v) as the solvent system. Consequently, three polar compounds including gallic acid, catechin, and gallic acid 4‐O‐β‐d ‐(6′‐O‐galloyl) glucoside were obtained with purities higher than 98%. The results showed glacial acetic acid could be such an appropriate regulator for the ethyl acetate/water system. This study provides a reference for the separation of polar compounds from natural products by high‐speed countercurrent chromatography.     

Protein Protection by Antioxidants: Development of a Convenient Assay and Structure‐Activity Relationships of Natural Polyphenols

In this work, a convenient test of antioxidant activity was developed, with BChE‐contaminated HSA as the target of AAPH‐induced oxidation and its esterase activity as the marker of protein integrity or degradation. The method is relatively simple, of low cost, and convenient to use. Its application to natural polyphenols showed that quercetin ( 1 ), verbascoside ( 2 ), chlorogenic acid ( 3 ), caffeic acid ( 4 ), 1,3,6,7‐tetrahydroxyxanthone ( 5 ), and mangiferin ( 6 ), are good antioxidants (IC₅₀<9 μM ). 1,5‐Dihydroxy‐3‐methoxyxanthone ( 7 ), flemichin D ( 8 ), and cordigone ( 9 ) showed modest activities (ca. 50 μM <IC₅₀<350 μM ), whereas danthrone ( 10 ) was inactive. Complementary experiments with two of the more active antioxidants, namely quercetin ( 1 ) and chlorogenic acid ( 3 ) showed that both antioxidants were better radical scavengers than chain‐breaking antioxidants. The relative adiabatic oxidation potential (ΔH_ox), the relative H‐bond dissociation energy (ΔH_abs), and the first oxidation potential measured by cyclic voltammetry were found to be related to the radical‐scavenging activity of these antioxidants.     

Flavonoid Glycosides from Terminalia catappa L.

Under the inhibition of Cu⁺²‐induced LDL oxidation‐guided fractionation, two new flavone glycosides with galloyl substitution were isolated from the dried fallen leaves of Terminalia catappa L. Their structures were established as apigenin 6‐C‐(2″‐O‐galloyl)‐β‐D‐glucopyranoside ( 1 ) and apigenin 8‐C‐(2″‐O‐galloyl)‐β‐D‐glucopyranoside ( 2 ), together with four known flavone glycosides, isovitexin, vitexin, isoorientin, and rutin, on the basis of spectroscopic method. Compounds 1 and 2 showed significant antioxidative effects. Their IC₅₀ were 2.1 and 4.5 μM, respectively.     

Diversity of Chemical Constituents from Saxifraga Montana H.

A thorough phytochemical investigation of the whole plant of Saxifraga montana H. afforded a new glucoside, methyl 6″‐O‐(E)‐p‐hydroxycinnamoxyl‐glucosyringate ( 1 ), and seventeen known natural products, 3‐methyl‐6‐methoxy‐3,4‐dihydroisocoumarin‐8‐O‐β‐D‐glucospyranoside ( 2 ), gallic acid ( 3 ), glucosyringic acid ( 4 ), daphnoretin ( 5 ), chamaejasmoside ( 6 ), myricetin ( 7 ), quercetin ( 8 ), quercetin‐3‐O‐β‐D‐galactopyranoside ( 9 ), quercetin‐3‐O‐α‐L‐arabinoside ( 10 ), quercetin‐3‐O‐β‐D‐glucospyranoside ( 11 ), rutin ( 12 ), quercetin‐3‐O‐β‐D‐glucopyranosyl (6‐1) glucopyranoside ( 13 ), ursolic acid ( 14 ), 5,28‐stigmastadien‐3β‐ol ( 15 ), β‐sitosterol ( 16 ), β‐daucosterin ( 17 ), 6′‐palmitoxyl‐β‐daucosterin ( 18 ). On the basis of various spectroscopic methods, especially intensive 2D‐NMR (COSY, HMQC and HMBC), FAB‐MS and HR‐ESI‐MS techniques, their structures were elucidated.     

Comprehensive evaluation of the antioxidant capacity of Sceptridium ternatum using multiple colorimetric methods and 1,1‐diphenyl‐2‐picrylhydrazyl–high‐performance liquid chromatography analysis

Sceptridium ternatum is a medicinal herb with multiple health benefits. However, its antioxidant activity and active components have not been clarified. In this study, the antioxidant capacity of S. ternatum was comprehensively investigated using multiple colorimetric methods and 1,1‐diphenyl‐2‐picrylhydrazyl–high‐performance liquid chromatography analysis. First, the phenolic content, flavonoid content, and radical scavenging ability of S. ternatum were parallelly determined using colorimetric methods performed in 96‐well microplates. The flavonoid content, rather than the phenolic content, was highly correlated with its antioxidant activity. Sceptridium ternatum was shown to be a rich source of flavonoids, with a highest flavonoid yield of 3.44 ± 0.11 mg/g. Subsequently, 1,1‐diphenyl‐2‐picrylhydrazyl–high‐performance liquid chromatography experiment and quadrupole time‐of‐flight mass spectrometry analyses were carried out for rapid screening of the individual antioxidants. A total of 14 O‐glycosyl flavonoids with quercetin or kaempferol aglycone have been characterized. Particularly, quercetin 3‐O‐rhamnoside‐7‐O‐glucoside exhibited the most potent antioxidant ability. Its half‐maximal effective concentrations for scavenging 1,1‐diphenyl‐2‐picrylhydrazyl and 2,2?‐azino‐bis (3‐ethylbenzthiazoline‐6‐sulfonic acid) radicals were 70.55 ± 2.69 and 106.90 ± 1.76 µg/mL, respectively, which were comparable with those of l ‐ascorbic acid. Our results indicated that the combined colorimetric and chromatographic methods provided a practical strategy for the discovery of bioactive compounds from natural products.     

New galloyl derivative from winged sumac (Rhus copallinum) fruit

Twelve compounds were isolated from Winged Sumac (Rhus copallinum) fruit and their structures were elucidated on the basis of NMR and mass spectral data. The isolates included a new galloyl derivative, (R)-galloyl malic acid dimethyl ester (1), and eleven known compounds, gallic acid (2), methyl gallate (3), glucogallin (4), methyl m-digallate (5), methyl p-digallate (6), quercetin (7), myricetin (8), rhamnazin (9), kaempferol (10), betulinic acid (11), and oleanolic acid (12). All of the compounds were evaluated for antiproliferative effects against human colon tumorigenic (HCT-116, Caco-2) and nontumorigenic (CCD18-Co) cell lines.     

Electrochemical Characterization of Epigallocatechin Gallate Using Square‐Wave Voltammetry

Electrochemical oxidation of (?)‐epigallocatechin gallate (EGCG), the main monomer flavanol found in green tea, has been investigated over a wide pH range at a glassy‐carbon electrode using square‐wave voltammetry (SWV). Square‐wave voltammograms of (?)‐epigallocatechin (EGC) and gallic acid have been studied as well. The I–E profile of EGCG, i.e. the oxidation potentials and the current responses of the first and the second peak, is pH dependent. The oxidation of EGCG is a quasireversible process over the studied pH range, which was also confirmed by the non‐linear relationship between the peak currents and squre root of frequency. The best SWV responses for EGCG were obtained at pH 2.0, frequency of 100 Hz, step of 2 mV and amplitude of 50 mV. Under these conditions, linear responses for EGCG were obtained for concentrations from 1×10^?7 M to 1×10^?6 M, and calculated LOD and LOQ for the first oxidation peak were 6.59×10^?8 M and 2.19×10^?7 M, respectively. The proposed electroanalytical procedure was applied for the determination of EGCG content in green tea. Developed SWV methodology represents a potential analytical tool in determination of catechins in tea samples.     

LC–MS/MS method for the simultaneous determination of ethyl gallate and its major metabolite in rat plasma

A simple, rapid and sensitive liquid chromatography–tandem mass spectroscopy (LC–MS/MS) method was developed and validated for the determination of ethyl gallate, a pharmacologically active constituent isolated from Lagerstroemia speciosa (Linn.) Pers. This method was used to examine the pharmacokinetics of ethyl gallate and its major metabolite gallic acid in rat plasma using propyl gallate as an internal standard. After precipitation of the plasma proteins with acetonitrile, the analytes were separated on a Zorbax SB‐C₁₈ column (3.5 μm, 2.1 × 50 mm) with an isocratic mobile phase consisted of methanol–acetonitrile–10 mM ammonium acetate (10 : 25 : 65, v/v/v) containing 0.1% formic acid at a flow rate of 0.25 mL/min. The Agilent G6410A triple quadrupole LC/MS system was operated under the multiple‐reaction monitoring mode using the electrospray ionization technique in negative mode. The lower limits of quantification of gallic acid and ethyl gallate of the method were 0.5 and 1.0 ng/mL. The intra‐day and inter‐day accuracy and precision of the assay were less than 8.0%. This method has been applied successfully to a pharmacokinetic study involving the intragastric administration of ethyl gallate to rats. Copyright © 2009 John Wiley & Sons, Ltd.     

5‐O‐Caffeoylshikimic acid from Solanum somalense leaves: Advantage of centrifugal partition chromatography over conventional column chromatography

Solanum somalense leaves, used in Djibouti for their medicinal properties, were extracted by MeOH. Because of the high polyphenol and flavonoid contents of the extract, respectively, determined at 80.80 ± 2.13 mg gallic acid equivalent/g dry weight and 24.4 ± 1.01 mg quercetin equivalent/g dry weight, the isolation and purification of the main polyphenols were carried out by silica gel column chromatography and centrifugal partition chromatography. Column chromatography led to 11 enriched fractions requiring further purification, while centrifugal partition chromatography allowed the easy recovery of the main compound of the extract. In a solvent system composed of CHCl₃/MeOH/H₂O (9.5:10:5), 21.8 mg of this compound at 97% purity was obtained leading to a yield of 2.63%. Its structure was established as 5‐O‐caffeoylshikimic acid by mass spectrometry and NMR spectroscopy. This work shows that S. somalense leaves contain very high level of 5‐O‐caffeoylshikimic acid (0.74% dry weight), making it a potential source of production of this secondary metabolite that is not commonly found in nature but could be partly responsible of the medicinal properties of S. somalense leaves.