Yuanfeng Wang

Glycosylation of Dietary Flavonoids Decreases the Affinities for Plasma Protein

The interaction between flavonoids and proteins has attracted great interest among researchers. However, few reports have focused on the structure-affinity relationship of flavonoids binding to proteins. This work mainly concerns the effect of glycosylation of flavonoids on the affinities for BSA. Four flavonoid aglycones (baicalein, quercetin, daidzein, and genistein) and their monoglycosides (baicalin, quercitrin, daidzin, and puerarin, genistin) and another poly glycoside (rutin) are studied for their affinities for BSA. The glycosylation of flavonoids significantly affects the quenching/binding process. In general, the glycosylation of flavonoids lowers the affinity for BSA by 1 to 3 orders of magnitude depending on the conjugation site and the class of sugar moiety. The glucopyranosylation (daidzin and genistin) of flavonoids lowered the affinity for BSA by 5-10 times. Rhamnosylation (quercitrin) of flavonoids, however, lowered the affinity for BSA by 5600 times. This result partly supports that flavonoid aglycones are more easily absorbed than flavonoid glycosides. Higher binding affinities for BSA are associated with higher antioxidant activities for flavonoids. Glycosylation also decreases the hydrophobicity of flavonoids, and hydrophobic interaction may play an important role in binding flavonoids to proteins.

Structure-affinity relationship of flavones on binding to serum albumins: effect of hydroxyl groups on ring A.

Four flavones (flavone, 7-hydroxyflavone, chrysin, and baicalein) sharing the same B- and C-ring structure but a different numbers of hydroxyl groups on the A-ring were studied for their affinities for BSA and HSA. The hydroxylation on ring A of flavones increased the binding constants (K(a)) and the number of binding sites (n) between flavones and serum albumins. The affinities of 7-hydroxyflavone for BSA and HSA were about 800 times and 40 times higher than that of flavone, respectively. It appears that the optimal number of hydroxyl groups introduced to the ring A of flavones is one. As more hydroxyl groups were introduced to positions at C-5, C-6, and/or C-7 of flavones, the affinities for serum albumins decrease. The critical energy transfer distances (R(0)) between the hydroxylated flavones (1-3 OH on the ring A) and serum albumins decreased with the increasing affinities for serum albumins.

Sugar compositions, α-glucosidase inhibitory and amylase inhibitory activities of polysaccharides from leaves and flowers of Camellia sinensis obtained by different extraction methods

The sugar compositions, α-glucosidase inhibitory and α-amylase inhibitory activities of polysaccharides from leaves and flowers of green tea (Camellia sinensis) obtained by hot water extraction (HWE), boiled water extraction (BWE) and enzymatic extraction (EE) were investigated. The yields, sugar contents and monosaccharide compositions of tea leaves polysaccharides (TLPS) and tea flower polysaccharides (TFPS) were all significantly affected by extraction methods. The contents of acidic polysaccharides (APS) extracted by BWE and EE were both much more than those by HWE. The yields of TLPS and TFPS were determined as EE>BWE>HWE. Enzyme and higher temperature could improve the contents of APS and yields of TLPS and TFPS. TLPS and TFPS were all mainly composed of Rha, Ara, Gal, Glu and GalA, very little molar contents of GluA, Xyl and Man. It seemed that enzyme extraction could be more conducive to increase the content of Ara, Gal and GaLA. The molecular weights of TFPS were larger than those of TLPS. The molecular weights of polysaccharides obtained by EE decreased. Proteins in tea leaves and tea flowers might be decomposed by EE by observing UV peaks and IR absorption. peaks. The α-glucosidase inhibitory and amylase inhibitory activities of TLPS and TFPS obtained by EE were lower than those by water extracted method. The inhibitory percentages of TLPS and TFPS against α-amylase were all lower than α-glucosidase for different extractions.

Antioxidant activities potential of tea polysaccharide fractions obtained by ultra filtration.

Three polysaccharide fractions (TPS1, TPS2 and TPS3) with different molecular weights were obtained using ultra filtration membranes from crude tea polysaccharide (CTPS) extracted from abandoned lower grade tea leaves. Each fraction contained different contents of neutral sugar, uronic acid, protein, and total polyphenols. These differences provided basis for the antioxidant and free radical scavenging activity of these polysaccharide fractions. The molecular weights of TPS1, TPS2, and TPS3 were around 2.40×10(5) Da, 2.14×10(4) Da, and 2.46×10(3) Da, respectively. In general, TPS1 and CTPS had stronger antioxidant activity, TPS2 and TPS3 had lower antioxidant activity. TPS1 had higher activity for DPPH and lipid per oxidation inhibition. But it had lower capacity for reducing power and metal chelating. This might be due to its higher content of hexuronic acid and larger molecular weight. The order of inhibition activity of lipid per oxidation of various polysaccharide fractions was the same as DPPH radical scavenging activity, as well as the order of metal chelating activity of various polysaccharide fractions similar to hydroxyl radical scavenging activity, which demonstrated that hydroxyl radical scavenging activity of polysaccharide relied heavily on the Fe(2+) metal chelating to decrease the generation of hydroxyl radical.

Which model based on fluorescence quenching is suitable to study the interaction between trans-resveratrol and BSA?

There are several models by means of quenching fluorescence of BSA to determine the binding parameters. The binding parameters obtained from different models are quite different from each other. Which model is suitable to study the interaction between trans-resveratrol and BSA? Herein, twelve models based fluorescence quenching of BSA were compared. The number of binding sites increasing with increased binding constant for similar compounds binding to BSA maybe one approach to resolve this question. For example, here eleven flavonoids were tested to illustrate that the double logarithm regression curve is suitable to study binding polyphenols to BSA.

Sulfation of tea polysaccharides: synthesis, characterization and hypoglycemic activity.

Neutral polysaccharides (NTPS) and acid polysaccharides (ATPS) from tea leaves were obtained on a D315 macroporous anion-exchange resin column chromatography. NTPS and ATPS were sulfated by the pyridine-sulfonic acid method to obtain NTPS-S and ATPS-S. It was found that NTPS was easier sulfated than ATPS. There are strong characteristic absorption peaks located in 1258 cm(-1), 1146 cm(-1), 832 cm(-1) and 617 cm(-1) in the FTIR spectra of sulfated polysaccharides. Sulfation of polysaccharides also affected the endothermic and exothermic peaks via the DSC scan analysis. The appearance of exothermic peaks in both NTPS-S and ATPS-S indicated that the redox reaction might happen. The comparative study of hypoglycemic effect on mice showed that the sulfation of polysaccharides significantly improved hypoglycemic activity.

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 1.1×10(5) and 2.4×10(5)Da, respectively. Se-TPS3 was a polysaccharide polymer with two peaks with molecular weights of 9.2×10(5) and 2.5×10(5)Da. 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.

Systematic investigation of the influence of CdTe QDs size on the toxic interaction with human serum albumin by fluorescence quenching method

Quantum dots (QDs) are complementary tools to the organic fluorescent dyes used in biological system. Investigation of QDs biological toxicity has attracted great interest for their depth application. Here, the fluorescence quenching method was used to investigate the influence of CdTe QDs size on the toxic interaction with human serum albumin (HSA). Two aqueous-compatible CdTe QDs with maximum emission of 535nm (green-emitting QDs, G-QDs, 2.04 nm) and 654 nm (red-emitting QDs, R-QDs, 3.79 nm) were tested. The fluorescence quenching results indicated that the quenching effect of QDs on HSA fluorescence depended on the size and the nature of quenching is not dynamic but probably static, resulting in forming QDs-HSA complexes. The binding constants and the number of binding sites between R-QDs and HSA were higher than those of G-QDs. The results illustrated that the size of CdTe quantum dots affected the affinity for HSA and the increasing size of QDs enhanced the affinity for HSA. The values of lgK(a) are proportional to the number of binding sites (n). This result confirms the method used here is suitable to study the toxic interaction between QDs and HSA.

Protective Effects of Tea Polysaccharides and Polyphenols on Skin

The protective effects of tea polysaccharides (TPS) and polyphenols (TPP) on skin were investigated. TPS1 (92% TPS), crude TPS2 (20% TPS), and TPP (98%) were tested. The abilities of TPS and TPP to protect the skin were assessed in four aspects: moisture absorption and retention, sunscreen, promoting the proliferation of fibroblast cells, and tyrosinase inhibitory effect. TPS and TPP absorbed and reserved moisture perfectly. TPS with higher purity had better moisture absorption and retention abilities. TPS1 hardly protected the skin from the suns ultraviolet (UV) rays and had little promoting effect on fibroblasts proliferation. TPP, however, protected skin against UV rays and enhanced proliferation of fibroblast cells significantly. TPP had good tyrosinase inhibitory effects; TPS showed weaker tyrosinase inhibitory effects with the purity increased. The results indicated that TPP and TPS had complementary advantages and they should be appropriately combined to achieve higher performance when applied as active components of cosmetics.

Study on the purification and characterization of a polysaccharide conjugate from tea flowers

In this paper, the crude polysaccharides from the flowers of tea plant (Camellia sinensis) (TFPS) extracted with hot water were fractionated on a DEAE Sepharose FF chromatography to get TFPS1 with a yield of 18%. The properties and chemical compositions of TFPS1 were analyzed with GC, HPGPC, IC, IR methods and its morphology was observed with atomic force microscopy (AFM). The results showed that TFPS1 was a neutral glycoprotein conjugate with a molecular weight 500kDa. The alanine, threonine, glycine, valine, serine, histidine, glutamic acid, histidine and tyrosine were found in TFPS1 and the total content was 2.03%. TFPS1 was consisted of rhamnose, arabinose, mannose, glucose and galactose, with a mole ratio of 1.0:2.9:0.5:1.3:3.3. Sugar backbone of TFPS1 may consist of glucose and galactose, but branched chain may consist of arabinose, galactose and rhamnose. The IR spectrum of TFPS1 revealed the typical characteristics of polysaccharides and protein. TFPS1 was spherical particle structure with a diameter of 50-70nm.