Simultaneous analysis of tea catechins, caffeine, gallic acid, theanine and ascorbic acid by micellar electrokinetic capillary chromatography

A micellar electrokinetic capillary chromatography (MEKC) method for the simultaneous analysis of five tea catechins, theanine, caffeine, gallic acid and ascorbic acid has been developed. The catechins are (-)-epicatechin, (+)-catechin, (-)-epigallocatechin, (-)-epicatechin gallate and (-)-epigallocatechin gallate. p-Nitrophenol serves as both reference and internal standard. All the components are separated within 13 min with a 57 cm uncoated fused-silica column. On-column detection was carried out at 200 nm. This method has been used to measure these compounds in fresh tea leaves and tea liquor. The limit of detection for all analytes ranged from 1 to 20 microg/ml.     

Simultaneous determination of catechins, caffeine and gallic acids in green, Oolong, black and pu-erh teas using HPLC with a photodiode array detector

A simple and fast HPLC method using a photodiode array detector was developed for simultaneous determination of four major catechins, gallic acid and caffeine. After multiple extractions with aqueous methanol and acidic methanol solutions, tea extract was separated within 20 min using a methanol-acetate-water buffer gradient elution system on a C(18) column. The sample extraction data demonstrated that the single extraction used in the previous studies with aqueous acetonitrile or methanol is not sufficient; the multiple extraction procedure is essential for the quantitative analysis of catechins, phenolic acids and caffeine in teas. Several green, Oolong, black and pu-erh teas were successfully analyzed by this method. The analytical results obtained indicated that green teas contain higher content of catechins [(-)-epigallocatechin gallate, (-)-epigallocatechin, (-)-epicatechin gallate, and (-)-epicatechin] than both Oolong, pu-erh and black teas because fermentation process during the tea manufacturing reduced the levels of catechins significantly. The fermentation process also remarkably elevated the levels of gallic acid in full-fermented pu-erh and black teas. Another interesting finding is the low level of caffeine in Oolong teas, especially in Fujian Oolong tea.     

A new norisoprenoid and other compounds from Fuzhuan brick tea

Fuzhuan brick tea, a kind of dark tea consumed mainly in the border regions of Southwestern and Northwestern China since the 1860s, is produced from the leaves of Camellia sinensis var. sinensis by microbial fermentation. From this special fermented tea, a new norisoprenoid, 3R,9R-oxido-5-megastigmene, was isolated, together with α-linolenic acid, strictin, isovitexin, astragalin, (+)-catechin, (-)-epicatechin, (-)-epicatechin gallate, (+)-gallocatechin, (-)-epigallocatechin, (-)-epigallocatechin gallate and gallic acid. The structures of the compounds were identified by spectroscopic means. The new compound didn't show any inhibition activity against the tested enteric pathogenic microorganisms at a concentration of 800 μg/mL by the hole plate diffusion method.     

Efficient procedure for isolating methylated catechins from green tea and effective simultaneous analysis of ten catechins,three purine alkaloids,and gallic acid in tea by high-performance liquid chromatography with diode array detection

Monomers of (−)-epigallocatechin (EGC), (−)-epigallocatechin gallate (EGCG), (−)-epicatechin (EC), (−)-epicatechin gallate (ECG), (−)-epigallocatechin 3-O-(3-O-methyl) gallate (EGCG3″Me) and (−)-3-O-methyl epicatechin gallate (ECG3′Me) (purity, >97%) were successfully prepared from extract of green tea by two-time separation with Toyopearl HW-40S column chromatography eluted by 80% ethanol. In addition, monomers of (−)-catechin (C), (−)-gallocatechin (GC), (−)-gallocatechin gallate (GCG), and (−)-catechin gallate (CG) (purity, >98%) were prepared from EC, EGC, EGCG, and ECG by heat-epimerization and semi-preparative HPLC chromatography. With the prepared catechin standards, an effective and simultaneous HPLC method for the analysis of gallic acid, tea catechins, and purine alkaloids in tea was developed in the present study. Using an ODS-100Z C₁₈ reversed-phase column, fourteen compounds were rapidly separated within 15 min by a linear gradient elution of formic acid solution (pH 2.5) and methanol. A 2.5–7-fold reduction in HPLC analysis time was obtained from existing analytical methods (40–105 min) for gallic acid, tea catechins including O-methylated catechins and epimers of epicatechins, as well as purine alkaloids. Detection limits were generally on the order of 0.1–1.0 ng for most components at the applied wavelength of 280 nm. Method replication generally resulted in intraday and interday peak area variation of <6% for most tested components in green, Oolong, black, and pu-erh teas. Recovery rates were generally within the range of 92–106% with RSDs less than 4.39%. Therefore, advancement has been readily achievable with commonly used chromatography equipments in the present study, which will facilitate the analytical, clinical, and other studies of tea catechins.     

High-performance liquid chromatography of aromatic compounds with photochemical decomposition and tris(2,2'-bipyridine)ruthenium(III) chemiluminescence detection

A novel high-performance liquid chromatographic method for the determination of aromatic compounds based on the on-line photochemical degradation and subsequent tris(2,2'-bipyridine)ruthenium(III) chemiluminescence detection has been developed. Chemiluminescence intensity depended upon the number of aromatic rings, UV irradiation time, and variety of substituted functional groups. One of the decomposition products of aromatic compounds by UV irradiation was identified as oxalic acid. As one application of this methodology, determination of catechins in tea has been shown. Calibration graphs, based on standard (-)-epicatechin and (-)-epigallocatechin gallate solutions, were linear over the range of 0.1-50 microM. The detection limits (signal-to-noise ratio=3) were 0.8 pmol for (-)-epigallocatechin gallate and 1.2 pmol for (-)-epicatechin. The high-performance liquid chromatography-chemiluminescence (HPLC-CL) detection method with a post-column photochemical reactor can be applied to the sensitive and selective determination of catechins in tea.     

Phenolic compounds of mountain tea from the Balkans: LC/DAD/ESI/MSn profile and content

Twenty-one samples of Sideritis species (S. scardica, S. raeseri, S. taurica, S. syriaca and S. perfoliata) from various locations on the Balkan Peninsula were evaluated for their chemical constituents. Chemical analyses were focused on secondary metabolites, particularly phenolic compounds, which have several roles in the plant physiological processes and have demonstrated significant health beneficial effects. The occurrence of hydroxycinnamic acids, phenylethanoid glycosides and flavonoids has been investigated in taxonomically related taxa of the genus Sideritis. A systematic method for phenolic compounds identification was developed using tandem mass spectrometry coupled to high performance liquid chromatography with diode array detection. Scanning for precursor ions of commonly found phenolics in Sideritis species using LC/MS11 with an ion trap instrument permitted the specific determination of hydroxycinnamic acid derivatives, and phenylethanoid and flavonoid glycosides. Further characterization of each phenolic compound was performed using MS/MS product-ion analysis and common-neutral-loss analysis. This on-line technique allowed identification of three hydroxycinnamic acid derivatives, eight phenylethanoid glycosides, and twenty-four flavonoid glycosides. All the taxa analysed produced very similar phenolic patterns characterized by the presence of 5-caffeoylquinic acid, lavandulifolioside, verbascoside, hypolaetin 7-O-[6'-O-acetyl]-allosyl(1-->2)glucoside, apigenin 7-(4"-p-coumaroylglucoside), 4'-O-methylisoscutellarein 7-O-[6'-O-acetyl]-allosyl(1-->2)glucoside, and minor amounts of isoverbascoside, apigenin 7-O-allosyl(1-->2)glucoside, isoscutellarein 7-O-allosyl-(1-->2)-[6"-O-acetyl]-glucoside, hypolaetin 7-O-allosyl-(1-->2)-[6"-O-acetyl]-glucoside and 4'-O-methylhypolaetin 7-O-[6'-O-acetyl]-allosyl-(1-->2)-[6"-O-acetyl]-glucoside. These results show that the investigated species are systematically very closely related. Phenylethanoid glycosides and flavonoid acetylglycosides are dominant and constitute 90% of the total phenolic compounds compared with hydroxycinnamic acid and flavonoid 7-O-glycosides. Principal component analysis (PCA) was performed for the nature and content of the different compounds to be correlated to the particular Sideritis species and also to the locations.     

Comparison of microemulsion electrokinetic chromatography and micellar electrokinetic chromatography methods for the analysis of phenolic compounds

In this study, microemulsion electrokinetic chromatography (MEEKC) and micellar electrokinetic chromatography (MEKC) were compared for their abilities to separate and detect thirteen phenolic compounds (syringic acid, p-coumaric acid, vanillic acid, caffeic acid, gallic acid, 3,4-dihydroxybenzoic acid, 4-hydroxybenzoic acid, (+)-catechin, (-)-epigallocatechin, (-)-epicatechin gallate, (-)-epigallocatechin gallate, (-)-epicatechin, and (-)-gallocatechin), and two other ingredients (caffeine and theophylline) in teas and grapes. Separation of phenolic compounds was improved by changing the SDS concentration for MEEKC, but the SDS concentration rarely affected the resolution for MEKC. Organic modifier (acetonitrile or methanol) was found to markedly influence the resolution and selectivity for both MEEKC and MEKC systems. In addition, a higher voltage and a higher column temperature improved the separation efficiency without any noticeable reduction in resolution for MEEKC whereas they caused a poor resolution for the MEKC system. Although separations with baseline resolution were achieved by the optimized MEEKC and MEKC methods, the separation selectivity resulting from the proposed MEEKC method was completely different from that of MEKC.     

Analyses of phenolic compounds by microemulsion electrokinetic chromatography

In this study, a microemulsion electrokinetic chromatography (MEEKC) method was developed to analyze and detect 13 phenolic compounds (syringic acid, p-cumaric acid, vanillic acid, caffeic acid, gallic acid, 3,4-dihydroxybenzoic acid, 4-hydroxybenzoic acid, (+)-catechin, (-)-epigallocatechin, (-)-epicatechin gallate, (-)-epigallocatechin gallate, (-)-epicatechin, and (-)-gallocatechin), which are present in many plant-derived foods. The effects of cosurfactant, organic modifier, and oil were examined in order to optimize the separation of these phenolic compounds. The amounts of cosurfactant (cyclohexanol) and organic modifier (acetonitrile) were determined as the major influence on the separation selectivity, while the type of oil partially affected the separation resolution of the phenolic compounds. A highly efficient MEEKC separation method was achieved within 14 min by using a microemulsion solution of pH 2.0 containing 2.89% w/v SDS, 1.36% w/v heptane, 7.66% w/v cyclohexanol, and 2% w/v ACN. Furthermore, the present work could demonstrate that the nature of the oil phase has a significant influence on the separation selectivity of phenolic compounds.     

Simultaneous determination of catechins, rutin, and gallic acid in Cistus species extracts by HPLC with diode array detection

A simple high-performance liquid chromatography method using a diode array detector (DAD) is developed for the simultaneous analysis of five major catechins: (+)-catechin (C), (-)-epicatechin (EC), (-)-gallocatechin (GCT), (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCG), and the phenolic plant metabolites gallic acid (GA) and rutin (RT) in lyophilized extracts of Cistus species. The optimal analytical conditions are investigated to obtain the best resolution and the highest UV sensitivity for the quantitative detection of catechins. The optimized conditions (acetonitrile-phosphate buffer 50mM, pH 2.5, gradient elution system on a C(18) reversed-phase column with a flow rate of 1 mL/min and UV absorbance at 210 nm) allowed a specific and repeatable separation of the studied analytes to be achieved. All compounds are successfully separated within 32 min. Calibration curves are linear in the 2-50 microg/mL range for GCT, C, and EGCG and in the 5-50 microg/mL range for GA, EGC, EC, and RT. The limit of detection values ranged from 0.24 to 0.74 microg/mL. The limit of quantitation limit values ranged from 0.77 to 1.94 microg/mL. The validated method is applied to the determination of the specific phytochemical markers GA, GCT, C, and RT in Cistus incanus and Cistus monspeliensis lyophilised extracts. The recovery values ranged between 78.7% and 98.2%. The described HPLC method appears suitable for the differentiation and determination of the most common catechins together with the glycoside rutin and the phenolic compound gallic acid and can be considered an effective and alternative procedure for the analyses of this important class of natural compounds.     

Microemulsion electrokinetic chromatography for the analysis of green tea catechins: effect of the cosurfactant on the separation selectivity

Microemulsion electrokinetic chromatography (MEEKC) was applied to the separation of six catechins and caffeine, the major constituents of the green tea. The developed methods involved the use of sodium dodecyl sulfate (SDS) as surfactant, n-heptane as organic solvent and an alcohol as cosurfactant. The separations were performed under acidic conditions (pH 2.5 phosphate buffer, 50 mM) to ensure good stability of the catechins, with reversed polarity (anodic outlet). The effect of the alcohol nature on the MEEKC selectivity was evaluated; nine alcohols were used as cosurfactant: 1-butanol, tert-butanol, 1-pentanol, 2-pentanol, 3-pentanol, cyclopentanol, 1-hexanol, 2-hexanol, and cyclohexanol. The migration order of (+)-catechin (C), (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-gallocatechin (GC), (-)-epigallocatechin gallate (EGCG), (-)-epicatechin gallate (ECG), caffeine and theophylline was significantly affected by the alcohol used as cosurfactant. Using nine microemulsions, four different selectivities were achieved: A (cyclohexanol); B (2-pentanol, 3-pentanol, 1-hexanol, 2-hexanol); C (1-butanol, 1-pentanol, cyclopentanol); D (tert-butanol). MEEKC methods, based on 2-hexanol and cyclohexanol as cosurfactant were validated and successfully applied to the analysis of catechins and caffeine in commercial green tea products.     

Development and application of UHPLC-MS/MS method for the determination of phenolic compounds in Chamomile flowers and Chamomile tea extracts

UHPLC-MS/MS method using BEH C18 analytical column was developed for the separation and quantitation of 12 phenolic compounds of Chamomile (Matricaria recutita L.). The separation was accomplished using gradient elution with mobile phase consisting of methanol and formic acid 0.1%. ESI in both positive and negative ion mode was optimized with the aim to reach high sensitivity and selectivity for quantitation using SRM experiment. ESI in negative ion mode was found to be more convenient for quantitative analysis of all phenolics except of chlorogenic acid and kaempherol, which demonstrated better results of linearity, accuracy and precision in ESI positive ion mode. The results of method validation confirmed, that developed UHPLC-MS/MS method was convenient and reliable for the determination of phenolic compounds in Chamomile extracts with linearity >0.9982, accuracy within 76.7-126.7% and precision within 2.2-12.7% at three spiked concentration levels. Method sensitivity expressed as LOQ was typically 5-20 nmol/l.Extracts of Chamomile flowers and Chamomile tea were subjected to UHPLC-MS/MS analysis. The most abundant phenolic compounds in both Chamomile flowers and Chamomile tea extracts were chlorogenic acid, umbelliferone, apigenin and apigenin-7-glucoside. In Chamomile tea extracts there was greater abundance of flavonoid glycosides such as rutin or quercitrin, while the aglycone apigenin and its glycoside were present in lower amount.     

Direct enantioseparation of catechin and epicatechin in tea drinks by 6-O-alpha-D-glucosyl-beta-cyclodextrin-modified micellar electrokinetic chromatography

Cyclodextrin-modified micellar electrokinetic chromatography was applied to the enantioseparation of catechin and epicatechin using 6-O-alpha-D-glucosyl-beta-cyclodextrin together with sodium dodecyl sulfate and borate-phosphate buffer. Factors affecting chiral resolution and migration time of catechin and epicatechin were studied. The optimum running conditions were found to be 200 mM borate-20 mM phosphate buffer (pH 6.4) containing 25 mM 6-O-alpha-D-glucosyl-beta-cyclodextrin and 240 mM sodium dodecyl sulfate with an effective voltage of +25 kV at 20 degrees C using direct detection at 210 nm. Under these conditions, the resolution (Rs) of racemic catechin and epicatechin were 4.15 and 1.92, respectively. With this system, catechin and epicatechin enantiomers along with other four catechins ((-)-catechin gallate, (-)-epicatechin gallate, (-)-epigallocatechin, (-)-epigallocatechin gallate) and caffeine in tea samples were analyzed successfully. The difference of migration time between catechin and epicatechin is discussed.     

Redifferentiation of human hepatoma cells induced by green tea polyphenols

A novel approach for the treatment of cancer is the differentiation therapy in which cancer cells are induced to attain a mature phenotype when exposed to differentiation inducers. To examine the effects of polyphenols extracted from green tea, i.e. ( – )-epicatechin (EC), ( – )-epigallocatechin (EGC), ( – )-epicatechin gallate (ECG) and ( – )-epigallocatechin gallate (EGCG), on the proliferation and redifferentiation of human hepatoma cell line SMMC-7721, we measured the changes of cell growth, cell surface charge and cell morphography after treament with green tea polyphenols. It was found that the growth curve of treated cells was decreased remarkably, cell surface charge of treated cells was decreased and the microvilli on the surface of treated cells were reduced obviously. It confirmed that green tea polyphenols could reverse malignant phenotypic characteristics and induced redifferentiation of SMMC-7721 cells. The ability of green tea polyphenols to inhibit reactive oxygen species (ROS)-mediated oxidative damage of DNA was also assessedin vitro by measuring the conversion of supercoiled pBR322 plasmid DNA to the open circular and linear forms. It was found that green tea polyphenols could significantly inhibit the oxidative damage of DNA induced by a water-soluble azo initiator 2,2-azobis(2-amidinopropane hydrochloride) (AAPH). However, they could promote the oxidative damage of DNA induced by H₂O₂ and Fe²⁺ at high concentrations. The relationship between the anti-cancer activity and antioxidation-prooxidation activity of green tea polyphenols is discussed.     

Uniformly-sized, molecularly imprinted polymers for (-)-epigallocatechin gallate, -epicatechin gallate and -gallocatechin gallate by multi-step swelling and polymerization method

Uniformly-sized, molecularly imprinted polymers (MIPs) for (-)-epigallocatechin gallate (EGCg), -epicatechin gallate (ECg) and -gallocatechin gallate (GCg) were prepared by a multi-step swelling and polymerization method using 2-vinylpyridine as a functional monomer, ethylene glycol dimethacrylate as a cross-linker and cyclohexanol as a porogen. Molecular recognition abilities of the obtained MIPs were evaluated in liquid chromatography using a mixture of ethanol and water, or ethanol as the eluent. Each MIP gave the highest molecular recognition ability for the respective template molecule. In addition, (-)-EGCg and -ECg had the same configuration (2R,3R) at positions 2 and 3, and therefore resulting in high cross reactivity each other. However, (-)-GCg, which has different configuration at position 2 with (-)-EGCg and -ECg, showed low cross reactivity with them. On the other hand, those MIPs showed no molecular recognition against (-)-epigallocatechin and -epicatechin, which have no gallate group at position 3. These results indicate that the MIPs prepared can recognize configuration at position 2 and a gallate group at position 3. Furthermore, the MIP for (-)-GCg could be successfully used for isolating (-)-EGCg and -ECg from green tea extract.     

Effect of tea catechins on the structure of lipid membrane and beta-ray induced lipid peroxidation

Inhibiting effect of four tea catechins, (−)-epicatechin (EC), (−)-epicatechin gallate (ECG), (−)-epigallocatechin (EGC), (−)-epigallocatechin gallate (EGCG), on the lipid peroxidation induced by β-ray in tritiated water was examined using a spin probe method. 16-Doxylstearic acid (16NS) was incorporated into the liposome prepared from egg yolk phosphatidylcholine and the rate of the decrease of ESR intensity of 16NS was used as a measure of the inhibiting effect. In the low concentration region below 10⁻⁵M, catechins showed their inhibitions on the lipid peroxidation according to the order of ECG>EGCG>EC>EGC. This result was explained by a model that the initiator of the peroxidation is the hydroxyl radical (·OH) and the catechins adsorbed on the lipid membrane surface acting as scavengers of ·OH. In the high concentration range, however, the effect was diverse and it decreased with the increase of it in the case of EGCG. EGCG in this range was considered to enter into the interior of the membrane and break the structure, which causes the decrease of 16NS. Observation with transmission electron microscope (TEM) revealed that the size of the liposome became larger with the increasing concentration of EGCG and finally it was broken into fragments, showing that EGCG broadened the area of the liposome as expected from the result of ESR.     

Effect of tea polyphenols on glucan synthesis by glucosyltransferase from Streptococcus mutans

In the course of our studies on the development of anti-plaque agents for prevention of dental caries, we investigated effects of some of tea preparations and their individual components on the glucan synthesis catalyzed by glucosyltransferase (GTF) from Streptococcus mutans. Extracts of green tea and black tea, and polyphenol mixtures showed appreciable inhibition in the synthesis of insoluble glucan. Among the components isolated from tea infusions, theaflavin and its mono- and digallates had potent inhibitory activities at concentrations of 1-10 mM against GTF. (+)-Catechin, (-)-epicatechin and their enantiomers had moderate inhibitory activities at these concentrations, while galloyl esters of (-)-epicatechin, (-)-epigallocatechin and (-)-gallocatechin had increased inhibitory activities.     

高效液相色谱法分析元宝枫叶中儿茶素类物质

本文建立了元宝枫树叶中儿茶素种类及其含量的高效液相色谱(HPLC)测定方法。采用反相C18色谱柱,以甲醇/水(含0.5%乙酸)=25/75(V/V)为流动相,对没食子儿茶素(GC)、表没食子儿茶素(EGC)、儿茶素(C)、表没食子儿茶素没食子酸酯(EGCG)、表儿茶素(EC)和没食子儿茶素没食子酸酯(GCG)进行定性、定量分析;以甲醇/水(含0.5%乙酸)=35/65(V/V)为流动相,对表儿茶素没食子酸酯(ECG)和儿茶素没食子酸酯(CG)进行定性分析,柱温均为35℃,检测波长为278 nm,流速为1.0mL/min。结果表明:元宝枫叶中有EGC、EC和GCG,其它五种则无。EGC平均含量为0.0389 mg/g,方法精密度(RSD)为0.42%(n=6);EC平均含量为0.0289 mg/g,方法RSD为1.5%(n=6);GCG平均含量为0.284 mg/g,方法RSD为0.32%(n=6)。该方法简便、准确、分离效果好,为元宝枫叶开发成茶叶、饮料以及医疗保健品提供重要依据。     

Stereoselective oxidation at C-4 of flavans by the endophytic fungus Diaporthe sp. isolated from a tea plant

The microbial transformation of five flavans (1-5) by endophytic fungi isolated from the tea plant Camellia sinensis was investigated. It was found that the endophytic filamentous fungus Diaporthe sp. oxidized stereoselectively at C-4 position of (+)-catechin (1) and (-)-epicatechin (2) to give the correspondent 3,4-cis-dihydroxyflavan derivatives (6, 10), respectively. (-)-Epicatechin 3-O-gallate (3) and (-)-epigallocatechin 3-O-gallate (4) were also oxidized by the fungus into 3,4-dihydroxyflavan derivatives (10, 12) via (-)-epicatechin (2) and (-)-epigallocatechin (11), respectively. Meanwhile, (-)-gallocatechin 3-O-gallate (5), (-)-catechin (ent-1) and (+)-epicatechin (ent-2), which possess a 2S-phenyl substitution, resisted the biotransformation.     

Determination of catechins and catechin gallates in biological fluids by HPLC with coulometric array detection and solid phase extraction

Tea polyphenols are well known for their beneficial health effects that involve their anti-carcinogenic, anti-mutagenic, anti-pathogenic and anti-oxidative properties. The main polyphenols of green tea are favan-3-ols (catechins) and their corresponding gallate compounds, which constitute about one-third of the dry weight of tea leaves. Their main ingredients are (+)-catechin (C), (−)-epicatechin (EC), (−)-gallocatechin (GC), (−)-epigallocatechin (EGC), (−)-catechin gallate (CG), (−)-epicatechin gallate (ECG), (−)-gallocatechin gallate (GCG) and (−)-epigallocatechin gallate (EGCG). Each has slightly different biological properties. We have developed a method to simultaneously analyze all these compounds in plasma and urine. The samples were first incubated with β-d-glucuronidase and sulfatase to release the catechin residues from their corresponding conjugates for subsequent extraction by selective solid phase column, Waters Oasis HLB extraction cartridges. The extracted molecules were resolved by reversed phase HPLC and monitored by coulometric chemical detection on a CoulArray detector. All eight catechin compounds were analyzed in a single chromatogram within 25 min. For plasma and urine analyses, good linearity (>0.9950) was validated in the range 10-2000 and 10-5000 ng/ml, respectively. The coefficients of variance (CV) were less than 5%. Absolute recovery was greater than 85% and detection limit was 5 ng/ml. The chromatogram exhibited minimal interference as a result of the highly selective solid phase extraction and CoulArray detection.     

Dietary burden of phenolics per serving of "Mountain tea" (Sideritis) from Macedonia and correlation to antioxidant activity

This work was afforded from 2 points of view, phytochemical evaluation and relation to antioxidant activity and dietary burden of phenolics of a cup of "Mountain tea", a drink obtained by domestic infusion of Sideritis. Phytochemically, two extraction protocols using water and methanol as solvent were used for comparison. Methanol and boiling water extracts (by domestic infusion procedure) showed that extracts were rich in bound forms of phenolics such as hydroxycinnamic acids, phenylethanoid glycosides and flavonoid glycosides. The total phenolic content for Sideritis species ranged around 190 mg per serving (2 g infusion bag) for methanol extracts and around 72 mg per serving in water extracts. Among the two different Macedonian Sideritis species, Sideritis raeseri (wild growing) showed the highest phenolics content in both extracts (212 mg and 89 mg per serving, respectively). Concerning the phenolic content in the different aerial parts, leaf was the richest plant organ in phenolics followed by flower and stem with the lowest amount. The methanol extract from Sideritis raeseri (wild growing) showed the highest antioxidant capacity as shown by DPPH, ABTS and FRAP assays. The antioxidant capacity was linearly correlated with phenolic content. Nutritionally, the dietary burden of phenolics of a "Mountain tea" bag for domestic infusion (serving size) was established at 89 mg for an homogeneous and equal distribution of the different aerial parts (leaf, flower and stem). However, and according to our results a rate of 60% leaf and 40% flower would increase the content of bioavailable phenolics and also the total phenolics content of a serving bag of "Mountain tea".