Se-enriched Tea Research Articles

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.

Catechins and Selenium Species-How They React with Each Other.

The combination of selenium and tea infusion, both with antioxidant properties, has potentially complementary mechanisms of action. Se-enriched tea has been considered as a possible Se supplement and a functional beverage to reduce the health risk of Se deficiency. This work investigated the interactions between plant catechins present in tea infusions and selenium species based on changes in the concentration of both reagents, their stability in aqueous solutions, and the possibilities of selenonanoparticles (SeNPs) formation. Selenium species exhibited instability both alone in their standard solutions and in the presence of studied catechins; selenocystine appeared as the most unstable. The recorded UV-Vis absorption spectra indicated the formation of SeNPs in the binary mixtures of catechins and selenite. SeNPs have also formed with diameters smaller than 100 nm when selenite and selenomethionine were added to tea infusions. This is an advantage from the point of view of potential medical applications.

Preparation, Physicochemical and Hypoglycemic Properties of Natural Selenium-Enriched Coarse Tea Glycoproteins.

Various functional components in tea have been well developed, but less research has been explored on glycoproteins in tea. In this paper, three types of glycoprotein fractions, namely tea selenium-binding glycoprotein1-1 (TSBGP1-1), TSBGP2-1, and TSBGP3-1, respectively, were extracted and purified from selenium-enriched coarse green tea. Chemical analysis revealed that three fractions were glycoproteins, but their selenium content, molecular weight, and monosaccharide composition were significantly different. Fourier transforms infrared (FT-IR) analysis indicated that three fractions contained characteristic absorption peaks of glycoproteins but differed in secondary structural composition. Thermogravimetric (TG) analysis showed that the thermal stability of the three fractions was dramatically distinct. The in vitro hypoglycemic activity showed that TSBGPs significantly activated the insulin receptor substrate 2 (IRS2)/protein kinase B (Akt) pathway in LO2 cells, then enhanced glucose metabolism and inhibited gluconeogenesis, and finally ameliorated insulin resistance (IR) and glucose metabolism disorders. Furthermore, Pearson correlation analysis reveals that the hypoglycemic activity was significantly correlated with Se, protein, monosaccharide composition (especially glucose), molecular weight, and secondary structure. Our results show that Se-enriched tea glycoprotein is a desirable candidate for developing anti-diabetic food, and TSBGP-2 and TSBGP-3 had a better regulation effect. Our results can provide a research reference for the extraction, physicochemical property, and function of selenium-enriched plant glycoproteins.

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.

Antitumor activity of Se-containing tea polysaccharides against sarcoma 180 and comparison with regular tea polysaccharides and Se-yeast

Selenium (Se)-containing polysaccharide, a Se-conjugate macromolecule, generally exhibited higher antitumor activity than its regular polysaccharide. Previously, we extracted Se-containing tea polysaccharides (Se-TPS) from Se-enriched tea, and explored its structure and antioxidant activity. In this study, we investigated antitumor activity of Se-TPS on sarcoma 180 (S-180), and compared with its regular polysaccharides TPS and dietary supplement Se-yeast. In vitro antitumor activity of Se-TPS was evaluated by MTT and LDH assays, and the results indicated that Se-TPS can significantly inhibit the proliferation of S-180 in dose-dependent manner (R2=0.97, p<0.0001). In S-180 cancer xenograft model in Kunming mice, Se-TPS oral administration at three doses of 50, 100 and 200mg/kg body weight daily for 13days resulted in significant tumor regression. At the same dose, Se-TPS exhibited significantly higher antitumor activity than TPS and Se-yeast. Importantly, Se-TPS can significantly increase the spleen and thymus indices of tumor-bearing mice, suggesting the safety and immunomodulatory activity of Se-TPS. Therefore, Se-TPS may be a desirable antitumor agent for therapeutic and immunomodulatory applications.

Microwave-Ultrasonic Synergistic Extraction of Crude Se-Polysaccharides from Se-Enriched Tea

Se-polysaccharides are organic Se-conjugated biological macromolecules with stronger biological activities than Se-free polysaccharides. Se-polysaccharides, as a kind of biological materials, can be extracted from Se-enriched tea and can increase the added value of tea production. Microwave–ultrasonic synergistic extraction exhibits the advantages of microwave and ultrasonic extraction and thus provides an economic and effective path for utilization of Se-polysaccharides. In this study, Se-polysaccharides were extracted from Se-enriched tea by microwave–ultrasonic synergistic method for the first time. The optimal condition was determined through single-factor experiment and L9(43) orthogonal experiment. Results showed that the optimal condition comprised the following: ratio of solvent to material of 20:1, microwave power of 250 W, extraction temperature of 60 °C, and extraction time of 210 s; under this condition, the extraction rate of Se-polysaccharides reached the maximum value of 4.56%. This study shows that microwave–ultrasonic synergistic extraction is an efficient technology for extracting Se- polysaccharides from Se-enriched tea.

Natural variation of selenium concentration in diverse tea plant (Camellia sinensis) accessions at seedling stage

Selenium (Se) is a dietary essential trace element for humans and animals. Owing to Se being obtained from food or other source of supplementation, Se-enriched tea is a possible source of supplemental Se and thus has been drawing much attention. This study aimed to identify the variation of the Se concentrations among 14 elite Camellia sinensis cultivars against two-Se-levels supplementation at seedling stage. In the present study, the genetic diversity was assessed by 93 alleles revealed by 12 SSR primers in the C. sinensis accessions. Among the scored 93 alleles, 81 (87.10%) were polymorphic, and the average Nei's gene diversity (He) was 0.253 and average shannon information index (I) was 0.394, indicating a relatively high genetic variation. Significant variations were observed for the Se concentration among the accessions in both treatments (P<0.01), ranging from 0.300–0.445mgkg−1 and 0.357–0.537mgkg−1 in control (0) and Se-supplied (4mgkg−1) treatments respectively. The quality components content, tea polyphenols and amino acid, were sensitive to Se-supplement in a few of accessions, whereas soluble sugar and aqueous extract content appeared unchanged between the contrast treatments. In addition, the genetic variation among the tea plant cultivars was not well correlated with the Se concentration. Even then, the genetic variation in Se concentration across the 14 accessions indicated the possibility of utilizing tea plant accessions to develop optimized cultivars for Se-enriched tea. For the relative high Se concentration in the tea, tea plant is supposed to be a Se-enriched species. These results may enhance our understanding the genetic variation in tea plant.

Extraction, characterization and antioxidant activities of Se-enriched tea polysaccharides

Se-polysaccharides from Se-enriched tea leaves were purified by DEAE–sepharose fast flow gel column (2.5×60cm) and three polysaccharide fractions (Se-TPS1, Se-TPS2, and Se-TPS3) were isolated and purified with yields of 6.5, 37.14, and 8.57%, respectively. The average sizes of Se-TPS1 and Se-TPS2 were determined by HPGPC system, with molecular weights of 1.1×105 and 2.4×105Da, respectively. Se-TPS3 was a polysaccharide polymer with two peaks with molecular weights of 9.2×105 and 2.5×105Da. Monosaccharide components analysis by ion chromatography revealed Se-polysaccharides were acidic polysaccharoses and different from each other in monosaccharide kinds and molar ratio. Elements of Se, C, H, N, S, and 14 kinds of mineral elements were analyzed by AFS, EA, and ICP-AES, respectively. Spectral analysis (IR and UV) indicated Se-polysaccharides were typical glycoproteins. Morphological analyses of the samples were determined by SEM and AFM. In addition, the DPPH and superoxide radicals scavenging activities were also discussed to assess antioxidant activities of the samples, and Se-polysaccharides showed higher antioxidant activities compared to the ordinary polysaccharides.

Effect of fertilization on selenium content of tea and the nutritional function of Se-enriched tea in rats

The present study examined the effect of fertilization with sodium selenite on the selenium content of tea and the nutritional function of Se-enriched tea. Selenium content of tea leaves was increased up to 0.36 μg g−1 by the application of sodium selenite to soil at 0.5 and 1.0 kg Se ha−1. Application by a Se-enriched organic manure at a rate of 0.5 kg Se ha−1 provided a higher biological availability of selenium for plant uptake compared with a similar amount of sodium selenite. Foliar spray of sodium selenite at 50–100 g Se ha−1 increased the selenium content to 0.32–1.45 μg g−1 in tea leaves sampled at the 8–26 days after spraying. Selenium content in the blood and liver, glutathione peroxidase activity in blood of rats were significantly enhanced by feeding of an extracted solution of Se-enriched tea leaves and sodium selenite. Glutathione peroxidase activity in liver of rats fed with Se-enriched tea was higher than that fed with sodium selenite, indicating that the selenium in Se-enriched tea leaves is a more effective Se source than sodium selenite. Increasing the Se level in food products through the application of a selenium fertilizer is a safe, effective and feasible means of increasing the selenium intake of human and animals in low selenium areas of China.

Physiological function of Se‐enriched tea fertilised with sodium selenite and naturally high‐Se tea in rats

In order to increase food selenium (Se) content, Se-enriched tea was produced by fertilising with sodium selenite in low-Se soil. Five groups of rats were fed a low-Se diet supplemented with either water (Se-deficient), sodium selenite or an aqueous extraction of low-Se tea, Se-enriched tea or naturally high-Se tea. The chemical form of Se in Se-enriched tea and the physiological function in rats fed the different Se sources were determined after 8 weeks. The results showed that organic Se accounted for 80% or more of the Se in Se-enriched tea fertilised with sodium selenite and naturally high-Se tea, but no significant differences in the proportion of organic Se and protein Se were found between Se-enriched tea and naturally high-Se tea. The Se biological utilisation rates were 65.41, 68.05 and 70.49% for sodium selenite, Se-enriched tea and naturally high-Se tea respectively. The Se content of blood and liver and the glutathione peroxidase (GSH-Px) activity were significantly increased by feeding Se-enriched tea and sodium selenite compared with low-Se tea, but a more efficient increase in liver GSH-Px activity was obtained with Se-enriched tea than with sodium selenite. No significant differences were found between Se-enriched tea fertilised with sodium selenite and naturally high-Se tea, which proved that the biological effectiveness of Se in Se-enriched tea was higher than that of sodium selenite in increasing liver GSH-Px activity. Se-enriched tea fertilised with sodium selenite in low-Se soil gave the same biological function as naturally high-Se tea. Therefore Se-enriched tea is a safe and effective means of increasing the Se intake of both humans and animals in low-Se areas. © 2000 Society of Chemical Industry

Physiological function of Se-enriched tea fertilised with sodium selenite and naturally high-Se tea in rats

In order to increase food selenium (Se) content, Se-enriched tea was produced by fertilising with sodium selenite in low-Se soil. Five groups of rats were fed a low-Se diet supplemented with either water (Se-deficient), sodium selenite or an aqueous extraction of low-Se tea, Se-enriched tea or naturally high-Se tea. The chemical form of Se in Se-enriched tea and the physiological function in rats fed the different Se sources were determined after 8 weeks. The results showed that organic Se accounted for 80% or more of the Se in Se-enriched tea fertilised with sodium selenite and naturally high-Se tea, but no significant differences in the proportion of organic Se and protein Se were found between Se-enriched tea and naturally high-Se tea. The Se biological utilisation rates were 65.41, 68.05 and 70.49% for sodium selenite, Se-enriched tea and naturally high-Se tea respectively. The Se content of blood and liver and the glutathione peroxidase (GSH-Px) activity were significantly increased by feeding Se-enriched tea and sodium selenite compared with low-Se tea, but a more efficient increase in liver GSH-Px activity was obtained with Se-enriched tea than with sodium selenite. No significant differences were found between Se-enriched tea fertilised with sodium selenite and naturally high-Se tea, which proved that the biological effectiveness of Se in Se-enriched tea was higher than that of sodium selenite in increasing liver GSH-Px activity. Se-enriched tea fertilised with sodium selenite in low-Se soil gave the same biological function as naturally high-Se tea. Therefore Se-enriched tea is a safe and effective means of increasing the Se intake of both humans and animals in low-Se areas. © 2000 Society of Chemical Industry