Selenium-enriched Tea Research Articles

Selenium-Mediated (-)-Epigallocatechin-3-Gallate Dynamics via Flavanone-3-Hydroxylase Regulation of Flavonoid Biosynthesis in Fu Tea (Camellia sinensis (L.) O. Kuntze).

Tea (Camellia sinensis (L.) O. Kuntze) is a highly selenium enrichment capacity plant; high selenium concentration contributes to the occurrence of oxidative stress and protein misfolding in tea plants, whereas flavonoids can chelate heavy metals to protect plants from oxidative stress caused by metal exposure. Nevertheless, the role of catechins in flavonoid synthesis and nutrient metabolism under selenium stress remains unidentified. Combining Word2vec and HNSW utilizing UHPLC-Q-Orbitrap HRMS-MS/MS to implement rapid matching annotation of the structural information on metabolites in Fu tea, we found that selenium-mediated changes in catechins in Fu tea were mainly associated with flavonoid biosynthesis pathways. The results demonstrated that selenium treatment increased benign selenol analogues (glutathioselenol) in tea and identified the novel selenopeptide PRSeMW (m/z 636.22571, Pro-Arg-SeMet-Trp) in selenium-enriched Fu tea samples to enhance the health benefits of tea. The selenium levels were negatively correlated with N5-ethyl-l-glutamine (11.63 to 4.26 mg kg-1) and (-)-epigallocatechin (13.26 to 11.19 mg kg-1), increasing the accumulation of tea polyphenols ((-)-catechin gallate, (-)-epigallocatechin 3-gallate, and (+)-gallocatechin), and decreasing the level of caffeine. These discoveries provide new insights into the mechanism of tea polyphenol-mediated transformation of selenium in Fu tea and theoretical support for the quality assessment of selenium-enriched tea.

Preparation, Characterization, and Antioxidant Properties of Selenium-Enriched Tea Peptides.

The research on the activity of selenium (Se)-enriched agricultural products is receiving increasing attention since Se was recognized for its antioxidant activities and for its enhancement of immunity in trace elements. In this study, antioxidant Se-containing peptides, namely, Se-TAPepI-1 and Se-TAPepI-2, were optimally separated and prepared from Se-enriched tea protein hydrolysates by ultrafiltration and Sephadex G-25 purification, and subsequently, their physicochemical properties, oligopeptide sequence, and potential antioxidant mechanism were analyzed. Through the optimization of enzymatic hydrolysis conditions, the Se-enriched tea protein hydrolyzed by papain exhibited a better free radical scavenging activity. After separation and purification of hydrolysates, the two peptide fractions obtained showed significant differences in selenium content, amino acid composition, apparent morphology, peptide sequence, and free radical scavenging activity. Therein, two peptides from Se-TAPepI-1 included LPMFG (563.27 Da) and YPQSFIR (909.47 Da), and three peptides from Se-TAPepI-2 included GVNVPYK (775.42 Da), KGGPGG (552.24 Da), and GDEPPIVK (853.45 Da). Se-TAPepI-1 and Se-TAPepI-2 could ameliorate the cell peroxidation damage and inflammation by regulating NRF2/ARE pathway expression. Comparably, Se-TAPepI-1 showed a better regulatory effect than Se-TAPepI-2 due to their higher Se content, typical amino acid composition and sequence, higher surface roughness, and a looser arrangement in their apparent morphology. These results expanded the functional activities of tea peptide and provided the theoretical basis for the development of Se-containing peptides from Se-enriched tea as a potential natural source of antioxidant dietary supplements.

An efficient and low-cost method for the determination of selenium in selenium-enriched tea by high-performance liquid chromatography coupled with 3,3′-Diaminobenzidine derivatization

In this study, a novel analytical method was developed and validated for the quantification of selenium in selenium-enriched tea. The various valence states of selenium present in tea were converted to Se(IV) through oxidation and reduction reactions. To chemically react with Se(IV), 3,3′-Diaminobenzidine (DAB) was employed to produce Se-DAB derivatives. These derivatives were then analyzed and quantified using high-performance liquid chromatography (HPLC) with a NH2 column specifically designed for the target compound. The peak area of Se-DAB exhibited excellent linearity within the concentration range of 0.01–50 μgmL−1 (R2 = 0.9999). The method demonstrated a limit of detection (LOD) of 0.01 mgkg−1 and a limit of quantification (LOQ) of 0.03 mgkg−1. Moreover, the recoveries of Se-DAB spiked at different concentrations ranged from 81.2 % to 96.7 %, with relative deviations (RSDs) of 0.72 %–4.23 % (n = 6). Additionally, the RSDs under different batches varied from 3.42 % to 8.57 % (n = 9). The method exhibits good stability and repeatability. The results obtained by applying the method to 24 samples of selenium-rich tea show high consistency with the AFS method. The difference range between the two methods is 0.017–0.027 mg/kg, with an average difference of 0.005 mg/kg. Furthermore, this method offers the advantage of flexibility in analyzing large quantities of green tea samples, while utilizing lower instrument and reagent costs. Therefore, it can be considered as a new and cost-effective method for detecting selenium content in selenium-rich tea.

Comparative transcriptomics provides novel insights into the mechanisms of selenium accumulation and transportation in tea cultivars (Camellia sinensis (L.) O. Kuntze).

Tea plants (Camellia sinensis) show discrepancies in selenium accumulation and transportation, the molecular mechanisms of which are not well understood. Hence, we aimed to conduct a systematic investigation of selenium accumulation and transportation mechanisms in different tea cultivars via transcriptome analysis. The Na2SeO3 and Na2SeO4 treatments improved selenium contents in the roots and leaves of three tea cultivars. The high selenium-enrichment ability (HSe) tea cultivars accumulated higher selenium contents in the leaves than did the low selenium-enrichment ability (LSe) tea cultivars. Transcriptome analysis revealed that differentially expressed genes (DEGs) under the Na2SeO3 and Na2SeO4 treatments were enriched in flavonoid biosynthesis in leaves. DEGs under the Na2SeO3 treatment were enriched in glutathione metabolism in the HSe tea cultivar roots compared to those of the LSe tea cultivar. More transporters and transcription factors involved in improving selenium accumulation and transportation were identified in the HSe tea cultivars under the Na2SeO3 treatment than in the Na2SeO4 treatment. In the HSe tea cultivar roots, the expression of sulfate transporter 1;2 (SULTR1;2) and SULTR3;4 increased in response to Na2SeO4 exposure. In contrast, ATP-binding cassette transporter genes (ABCs), glutathione S-transferase genes (GSTs), phosphate transporter 1;3 (PHT1;3), nitrate transporter 1 (NRT1), and 34 transcription factors were upregulated in the presence of Na2SeO3. In the HSe tea cultivar leaves, ATP-binding cassette subfamily B member 11 (ABCB11) and 14 transcription factors were upregulated under the Na2SeO3 treatment. Among them, WRKY75 was explored as a potential transcription factor that regulated the accumulation of Na2SeO3 in the roots of HSe tea cultivars. This study preliminary clarified the mechanism of selenium accumulation and transportation in tea cultivars, and the findings have important theoretical significance for the breeding and cultivation of selenium-enriched tea cultivars.

Speciation of Selenium in Selenium-Enriched Foods by High-Performance Liquid Chromatography-Inductively Coupled Plasma-Tandem Mass Spectrometry

Herein, a method was established for the speciation of six selenium species by high performance liquid chromatography-inductively coupled plasma-tandem mass spectrometry (HPLC-ICP-MS/MS). The factors affecting separation were carefully investigated, including ionic strength, pH, and methanol content. Six species of selenium could be completely separated within 20 min, under the mobile phase of 25 mM citric acid in pH = 4.0 containing 2% methanol. The detection limits of selenite (Se(IV)), selenate (Se(VI)), selenomethionine (SeMet), selenocystine (SeCys2), methylselenocysteine (MeSeCys), and selenoethionine (SeEt) were 0.04, 0.02, 0.05, 0.02, 0.03, and 0.15 ng mL−1, respectively. To verify the practicality of this method, the analysis of selenium-enriched foods such as selenium-enriched spring water, selenium-enriched salts, and selenium-enriched tea were conducted, and recovery of 93.7–105% was achieved with RSD < 5%, revealing the high practical utility of the proposed method.

Polysaccharides in Selenium-Enriched Tea: Extraction Performance under Innovative Technologies and Antioxidant Activities.

Pulsed electric fields (PEF) and ultrasonic-assisted extraction (UE) were applied to improve the extraction performance of selenium-enriched tea polysaccharides (Se−TPSs) in mild conditions. Two combined extraction processes were investigated: (1) PEF strength at 10 kV/cm followed by conventional extraction (CE) at 50 °C for 60 min and (2) PEF+UE (PEF strength at 10 kV/cm followed by UE at 400 W for 60 min). The optimal extraction yields, and energy consumption rates were obtained at 36.86% and 41.53% and 78.78 kJ/mg and 133.91 kJ/mg, respectively. The Se−TPSs were analyzed and characterized by GPC, UV, and FT-IR, which evidenced the structural stability of the Se−TPSs during the extraction processes. It was found that PEF and UE could reduce the particle size diameter of the Se−TPS extract, as well as the proportion of uronic acid. Moreover, PEF could increase the selenium content in the Se−TPS extract by 160.14% due to a lower extraction temperature compared to conventional extraction. The antioxidant activities of the Se−TPSs in vitro were investigated using OH, , and scavenging experiments, as well as a total antioxidant ability evaluation. It was found that the antioxidant activity of the Se−TPSs obtained using PEF2+CE2 was relatively high due to the potential synergistic effect between the selenium and polysaccharides. Based on these results, we speculate that PEF2+CE2 was the best extraction process for the Se−TPSs. Furthermore, this research indicates the application of selenium-enriched tea for functional food production.

Protective effects of epigallocatechin-3-o-gallate combined with organic selenium against transforming growth factor-beta 1-induced fibrosis in LX-2 cells.

In this study, we investigated the protective effects and possible mechanism of epigallocatechin-3-o-gallate (EGCG) combined with organic selenium in transforming growth factor (TGF)-β1-activated LX-2 cells. After 12 h of starvation, LX-2 cells were treated with 10ng/ml of recombinant TGF-β1 and different concentrations of EGCG, L-selenomethionine (L-SeMet), or L-selenomethylcysteine (L-SeMC) for 24 h. We found that 100 and 200 μM EGCG combined with 1 mM L-SeMet or L-SeMC showed a synergistic effect in decreasing the survival rate of activated LX-2 cells. In addition, the combination of 100 mM EGCG and 1 mM L-SeMet or L-SeMC promoted the apoptosis of activated LX-2 cells. Compared with the EGCG treatment group, the combination intervention group had significantly suppressed levels of hepatic stellate cell activation markers including alpha-smooth muscle actin, collagen type I alpha 1, collagen type III alpha 1, 5-hydroxytryptophan (5-HT), and 5-HT receptors 2A and 2B. Moreover, interleukin-10 levels were decreased, while TGF-β1 levels were increased after TGF-β1 activation in LX-2 culture medium, whereas the combin1ation intervention reversed this phenomenon. The combination treatment had a more pronounced effect than any single treatment at the same dose. These results demonstrated that the combination of EGCG and organic selenium synergistically improves the TGF-β1-induced fibrosis of LX-2 cells to some extent by promoting apoptosis and inhibiting cell activation. PRACTICAL APPLICATIONS: Here, we found that the effects of epigallocatechin-3-o-gallate (EGCG) + L-selenomethionine or L-selenomethylcysteine were more pronounced than those of EGCG alone. Future studies should investigate the protective effects of green tea and selenium-enriched green tea against hepatic fibrosis and explore the differences in their molecular mechanisms. The results of this study will be helpful for the development and utilization of selenium-enriched tea for food processing and health supplement production.

Integrative Transcriptome and Proteome Analysis Reveals the Absorption and Metabolism of Selenium in Tea Plants [Camellia sinensis (L.) O. Kuntze

Certain tea plants (Camellia sinensis) have the ability to accumulate selenium. In plants, the predominant forms of bioavailable Se are selenite (SeO32–) and selenate (SeO42–). We applied transcriptomics and proteomics to hydroponically grown plants treated with selenite or selenate for 48 h in the attempt to elucidate the selenium absorption and assimilation mechanisms in tea. A total of 1,844 differentially expressed genes (DEGs) and 691 differentially expressed proteins (DEPs) were obtained by comparing the Na2SeO3 and Na2SeO4 treatments against the control. A GO analysis showed that the genes related to amino acid and protein metabolism and redox reaction were strongly upregulated in the plants under the Na2SeO3 treatment. A KEGG pathway analysis revealed that numerous genes involved in amino acid and glutathione metabolism were upregulated, genes and proteins associated with glutathione metabolism and ubiquinone and terpenoid-quinone biosynthesis were highly expressed. Genes participating in DNA and RNA metabolism were identified and proteins related to glutathione metabolism were detected in tea plants supplemented with Na2SeO4. ABC, nitrate and sugar transporter genes were differentially expressed in response to selenite and selenate. Phosphate transporter (PHT3;1a, PHT1;3b, and PHT1;8) and aquaporin (NIP2;1) genes were upregulated in the presence of selenite. Sulfate transporter (SULTR1;1 and SULTR2;1) expression increased in response to selenate exposure. The results of the present study have clarified Se absorption and metabolism in tea plants, and play an important theoretical reference significance for the breeding and cultivation of selenium-enriched tea varieties.

Effects of Enshi Selenium-rich Tea Combined with Gynostemma Pentaphyllum and Apenma on Lipid Reduction in Hyperlipemia Mice

Objective: To investigate the effects of tea blend composed of Enshi selenium-rich tea, gynostemma pentaphyllum and apenma on blood lipid and lipid metabolism in mice with hyperlipidemia and prevention of hyperlipidemia in mice on the high-fat diet. Methods: Mice were randomized into 7 groups, among which 6 groups were fed with high-fat diet to establish a hyperlipidemia mouse model, and the other group was fed with normal diet as the normal control. After the hyperlipidemia model was established, mice were fed with normal diet while receiving different regimens. The normal diet group, the high-fat control group and the positive control group were given physiological saline solution, physiological saline solution and atorvastatin daily by gavage, respectively. The initial intervention group was given medium dose tea blend solution by gavage, and the other three groups were given low, medium and high dose of tea solution daily by gavage, respectively. After 4 weeks of treatment, mice were sacrificed, blood samples were taken for monitoring of lipid metabolism, -liver and tissue tissues were removed for examination of morphology and gene expression. Results: The tea blend not only significantly reduced the level of blood lipid in hyperlipidemia mice, but also effectively protected the liver and kidney function (P < 0.05). Observation under the light microscope reveled that, high-fat diet led to the accumulation of fat in hepatocytes and disorder of hepatic cordage, while the tea blend alleviated the hepatocyte steatosis. In addition, the tea blend promoted the expression of HL and HSL genes, and increased the levels of LAXR and PPARA, which regulated lipid metabolism at the genetic level (P < 0.05). Conclusion: This study confirmed that drinking tea blend composed of Enshi selenium-enriched tea, Gynostemma pentaphyllum and Apocynum venetum could lower blood lipids in mice with hyperlipidemia. In addition, various doses of tea blend could be used for hyperlipidemia with good liver and kidney function, and medium or high dose of tea blend was relatively safe for hyperlipidemia with poor liver and kidney function.

Research on Strategies for the Development of Selenium-enriched Tea in Ankang City of Shaanxi Province in the Context of Targeted Poverty Alleviation

Research on Strategies for the Development of Selenium-enriched Tea in Ankang City of Shaanxi Province in the Context of Targeted Poverty Alleviation

Effect of selenium on tea (Camellia sinensis) under low temperature: Changes in physiological and biochemical responses and quality

Tea is a high-value cash crop, and it is a popular beverage globally owing to its unique flavor and health benefits. Selenium can increase tea yield, and the increasing demand for selenium-enriched tea has made it a research hotspot. However, the effect of selenium on the quality and cold resistance of tea has rarely been studied. The purpose of this study was to examine the effects of exogenous selenium application on the physiological and biochemical properties, antioxidant enzyme activity, and quality of tea under low-temperature stress (4℃). The results showed that selenium treatment increased the net photosynthetic rate of leaves under low-temperature stress. Furthermore, it reduced the contents of malondialdehyde and hydrogen peroxide to stabilize plant photosynthesis and the membrane system and to improve the cold tolerance of tea.Moreover, selenium treatment regulates the content of proline and increases the activities of superoxide dismutase, ascorbate peroxidase, peroxidase and catalase to prevent oxidative damage caused by cold stress. In addition, treatment with selenium regulated changes in the secondary metabolites of tea under low-temperature stress, including reducing the oxidation products of polyphenols, increasing the polyphenol content, increasing sugar accumulation, and promoting the synthesis of various tea amino acids to improve tea quality.

Preparation, physicochemical characterization and identification of two novel mixed ACE-inhibiting peptides from two distinct tea alkali-soluble protein

In this study, two novel mixed ACE-inhibiting peptides, namely Se-TAPep 1 and TAPep 1, were prepared and purified from selenium-enriched and common alkali-soluble proteins using a series of process, and then its physicochemical properties and oligopeptide sequence were analyzed. The results showed that Se-TAPep 1 and TAPep 1 could be successfully separated, but their ACE inhibitory activities were different (IC50 values were 13.39 mg/mL and 23.56 mg/mL, respectively), this may be related to the difference in selenium content. Further analysis of physicochemical properties showed that the protein or peptide fractions contained their characteristic absorption peaks and contained aromatic amino acids, while the apparent morphology was different, the presence of selenium could change the apparent morphology of protein or polypeptide fractions, arranging of selenium-enriched fractions more irregular. The amino acid composition analysis showed that the Pro content of the selenium-enriched fractions was higher than that of the ordinary component, whereas the oligopeptide sequence analysis showed that both LQPSLGFP derived from Se-TAPep 1 and AETGEIKGHY derived from TAPep 1 contained some characteristics of highly active ACE-inhibiting peptides, but the characteristics of LQPSLGFP were more conspicuous, which may be related to its molecular weight and source of mixed peptides. These findings indicated that the selenium-enriched tea mixed peptides had better potential uses than ordinary tea mixed peptides in the preparation of functional food.

Characterization of selenium-containing polysaccharides isolated from selenium-enriched tea and its bioactivities

Two novel selenium polysaccharide fractions (SeTPS-1 and SeTPS-2) were isolated purified, characterized from Se-enriched tea. The results showed that the molecular weights and Se content of SeTPS-1 and SeTPS-2 were 1.7 × 104 Da, 1.3 × 104 Da, and 23.50 μg/g and 13.47 μg/g, respectively. SeTPS-1 and SeTPS-2 had absorption spectra typical of selenium esters. SeTPS-1 was composed of glucose and galactose at a molar ratio of 80.1:2.3, respectively, while SeTPS-2 was composed of arabinose, glucose, galactose and galacturonic acid with a molar ratio of 2.04: 48.83: 3.21: 1.30, respectively. Both SeTPS-1 and SeTPS-2 adopted a random coil conformation. Importantly, in vitro assessment of the antioxidant capacity revealed that SeTPS-1 is a more potent antioxidant compared to SeTPS-2. Both compounds were effective at reducing DNA damage induced by H2O2. The promising data suggesting that these compounds confer natural protection against DNA-damaging agents, thereby contributing to the functional food qualities of tea.

Comparative analysis of existence form for selenium and structural characteristics in artificial selenium-enriched and synthetic selenized green tea polysaccharides

In recent years, selenium-enriched polysaccharides (Se-PS) have been paid more and more attention, and the activity of many Se-PSs has been studied but little on their structure. This study aimed to investigate the activity, structural characterization and present forms of selenium in two different artificial selenium-enriched tea polysaccharides (Se-TPS). The physicochemical analysis showed that both CSe-tps1 and ASe-tps1 were acidic heteropolysaccharides with different monosaccharide composition, molar ratio, and selenium content. Structural investigations including FT-IR, Raman spectra and 1D, 2D NMR analysis revealed that selenium in CSe-tps1 replaced the hydroxyl group at the C-6 position in the polysaccharide with the form of selenyl ester, while most of the selenium in ASe-tps1 replaced the hydroxyl group at the C-1 and C-6 position in the form of the SeH bond on the branch of the polysaccharide. Besides, a series of studies on the structural characteristics of the Congo red test, I2-KI reaction, FESEM, DSC, and XRD analysis showed that the two artificial Se-TPSs had a triple helix structure and more branches. However, there were significant differences in crystal morphology, apparent morphology, heat release ability, and the α-glucosidase inhibition activity. These results indicated that the difference in artificial selenization methods not only made the polysaccharide exhibit different structural characteristics and the hypoglycemic activity, but also had a significant effect on the form of selenium in polysaccharides.

Inhibitory Effects and Molecular Mechanisms of Selenium-Containing Tea Polysaccharides on Human Breast Cancer MCF-7 Cells

Dietary supplementation of selenium-enriched tea is known to have an anticancer health benefit. This study was to investigate the inhibitory effect of selenium-containing tea polysaccharides (Se-GTPs) from a new variety of selenium-enriched Ziyang green tea against human MCF-7 breast cancer cells. Se-GTPs dose-dependently exhibited an effective cell growth inhibition with an IC(50) of 140.1 μg/mL by inducing MCF-7 cancer cells to undergo G2/M phase arrest and apoptosis. The blockade of cell cycle was associated with an up-regulation of p53 expression, but not CDK2. Se-GTPs clearly triggered the mitochondrial apoptotic pathway, as indicated by an increase in Bax/Bcl-2 ratio and subsequent caspase-3 and caspase-9 activation. It was also found that the generation of intracellular ROS is a critical mediator in Se-GTPs-induced cell growth inhibition. These findings suggest that Se-GTPs may serve as a potential novel dietary agent for human breast cancer chemoprevention.

Quantitative Analysis of ATP Sulfurylase and Selenocysteine Methyltransferase Gene Expression in Different Organs of Tea Plant (&amp;lt;i&amp;gt;Camellia sinensis&amp;lt;/i&amp;gt;)

Tea plant (Camellia sinensis) has unique biological features for the study of cellular and molecular mechanisms, an evergreen broad-leaved woody plant which can accumulate selenium in soil abundant of Selenium. Expression of the genes related to Selenium (Se) metabolism is an adaptation to the soil environment for a long period. The purpose of the present study was to explore if there exist differences of expression about these genes in tea plant between growing in Selenium-abundant and normal soil. A quantitative real-time reverse transcription polymerase chain reaction (Q-RT-PCR) assay was done for quantification of ATP sulfurylase (APS) and selenocysteine methyltransferase (SMT) mRNA normalized to Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene in tea plant. Young leaves, mature leaves and tender roots from tea plants growing in soil abundant of Selenium were respectively obtained from Shitai County, Anhui Province, and also the relevant materials of the selenium un-enriched tea plant planted at agricultural garden of Ahui Agriculture University were taken as control for real-time PCR analysis. The results showed that APS1, APS2 and SMT expression levels for either young or mature leaves in selenium-enriched tea plant were lower than that in ordinary (selenium un-enriched) tea plant. In contrast, the APS1, APS2 and SMT expression level of roots in selenium-enriched tea plant were all higher than that in ordinary tea plant. APS1 gene expression level of roots in selenium-enriched tea plant was about 1.6 times higher than that in the ordinary tea plant, APS2 gene expression level was about 4.8-fold higher than that in the ordinary tea plant, SMT gene expression level was about 3.3 times higher than that in the ordinary tea plant. Among various tissues of selenium-enriched tea plant, APS1 gene relative expression level of young leaves was similar to or slightly higher than mature leaves, and the one of roots was the lowest among them; APS2 gene relative expression level of young leaves was similar to or slightly higher than the roots, and the one of mature leaves was the lowest among them; SMT gene relative expression level of young leaves was similar to or slightly higher than mature leaves, and the one of roots was the highest among them. Our results suggest that there existed correlation between selenium and expression levels of these genes.

Correlation of Dispersibility of Proteins with that of Selenium in Teas

Selenium-enriched tea was suggested as a possible source of supplemental Se. The result of this study indicates that it is not practicable to make selenium-enriched tea as a beverage like traditional green tea or black tea for the supplementation of selenium in human diet. The selenium dispersibilities of fresh tea leaves, green tea, and black tea highly correlated with those of protein (r(2) = 0.998). The high protein dispersibility (85.0%) of fresh tea leaves in water solution was accompanied by that of selenium (93.8%). Decreases in protein dispersibility of green tea and black tea to 2.5% and 4.2 % coincided with those of selenium to only 8.3% and 10.1%, respectively. The amount (14.90 μg) of selenium in saturated ammonium sulphate (a protein precipitating reagent) precipitate was 83.8% of that (17.79 μg) in fresh tea leaf extract, and after the saturated ammonium sulphate precipitate was dialyzed against distilled water overnight, the amount (14.37 μg) of selenium remaining in the dialyzed precipitate (protein) was still 80.8% of that in the fresh tea leaf extract. However, there were no significant differences (p >0.05) between the amount of selenium in the saturated ammonium sulphate precipitate and that in the saturated ammonium sulphate precipitate that was dialyzed.

Antioxidant activities of crude tea polyphenols, polysaccharides and proteins of selenium-enriched tea and regular green tea

The crude tea polyphenols, polysaccharides and proteins of regular green tea and Se-enriched green tea were investigated in vitro for antioxidant activities by auto-oxidation test (AAPH) and α,α-diphenyl-β-picrylhydrazyl (DPPH) radical scavenging method. Results showed that crude tea polyphenols of Se-enriched green tea provided the highest antioxidant activity by DPPH assay and the antioxidant activity was decreased in the order: crude tea polyphenols > crude tea proteins > tea polysaccharides. The crude protein of Se-enriched green tea was found to exhibit the highest antioxidant activity by AAPH method and the antioxidant activity was decreased in the order: crude tea proteins > tea polyphenols > tea polysaccharides. Tea polyphenols and tea polysaccharides of Se-enriched green tea presented significantly higher antioxidant activities than that of regular green tea. No significant difference of antioxidant activities was found between crude tea proteins of Se-enriched green tea and regular green tea. The combinations of Se with tea polyphenols and tea polysaccharides were responsible for the higher antioxidant activities of Se-enriched green tea than regular green tea.