| Tea polysaccharides (TPS), which contain neutral polysaccharide and acidic polysaccharide with molecular distribution from 4×10~4～10×10~4, were defined as the sum of bioactivity polysaccharides extracted from tea. The pigment, polysaccharides and some small molecular substance such as monosaccharides and oligosaccharides in primary products of polysaccharides cause difficulty in purifying tea polysaccharides and investigating the bioactivity of it. The article investigated the extraction process, quantitative method, fingerprint, hypoglycemic bioactivity, hypolipidemic bioactivity and antitumor bioactivity of TPS.Water extraction process of tea polysaccharides was optimized using the response surface analysis method. Results indicated that extraction temperature significantly affect the polysaccharides extraction ratio among the three main factors of extraction time, extraction temperature and water/material ratio. Ridge analysis indicated the optimum condition was 80℃, 1.5 h, 1:20, at which the extraction ratio of tea polysaccharides was 1.22 % with 2 % RSD. The optimum parameters were found containing credibility and practicality.Four different treatments including water-extracted process, pectase-extracted process, trypsin-extracted process and combined-enzyme-extracted process were respectively applied to extract TPS from Laoshan green tea. The extract ratio of combined-enzyme process method reached 5.17±0.17 % and higher than those of the three other process method. The crude TPS obtained from the four process method were further purified through Sepharose FF and the purified TPS was obtained respectively. Then comparisons on the components of monosaccharides, amino acids in the purified TPS were conducted. The four process method had no influence on the kinds of monosaccharides in tea polysaccharides, but little on the proportion of the monosaccharisdes. The total sugar content of TPS prepared by the four process method was decreased in following pectase-extracted process, combined-enzyme-extracted process, trypsin-extracted process, and water-extracted process. Especially, in pectase-extracted process it reached to 95.26±4.09%, while the uronic acids content decreased greatly. The four process method had no influence on the kinds of amino acids in TPS, but great on the proportion of them.TPS from diferent kinds of tea contain similar composition of sugars and amino acids. Polysaccharide part of tea TPS is mainly composed of arabinose, galactose and glucose with the approximate molar ratio of 1:1:0.5, uronic acid content in tea TPS was near 17～23 %. Protein part of tea TPS is composed of 16 normal amino acids among which Val, Ala, Gly, Glu are the major proportion. Based on the results, the purified TPS was used as the calibration standard in phenol sulfuric acid reaction for the calibration curve that was constructed by plotting absorbance versus mass of TPS with a correlation coefificient of 0.9961. In the developed method, TPS mass recovery ranges from 84.88 to 95.7% with a relative standard deviation of 5.53%. It is found that the developed method is simple, rapid, reliable and ideally suitable for quantifying TPS from green tea or oolong tea.High performance gel permeation chromatography (HPGPC) and component analysis revealed the molecular weight distribution and constituents of TPS I, TPS II and TPS III indicating that a 100 ~ 120 KDa fraction, was essentially composed of polysaccharides (~90%) of substantial amounts of arabinogalactan proteins.The second derivative IR spectra fingerprint of TPS from green tea was founded. The second derivative IR spectra of TPS I, TPS II and TPS III appear the intensity of peak around 1075, 1045 cm?1, which characterize galactopyranose in the backbone and arabinofuranose units in side branches of arabinogalactan proteins, respectively.Vectorial angle method was used for evaluating the similarity between two spectral fingerprints. Spectrogram can be treated as vector of hyperspace, and the similarity between them can be counted according to vectorial angle formula. The more near to 1 the value of cosθis, the more similar are the two vectors. In the article, the second derivative IR spectra of 1200–800 cm?1 region were used in calculating the similarity of two Spectrogram. Compared with the second derivative IR spectra of TPS II and TPS III, the value of cosθis 0.82. Compared with the second derivative IR spectra of TPS I和TPS III, the value of cosθis 0.26. Compared with the second derivative IR spectra of TPS II and TPS I, the value of cosθis 0.52. The values of cosθb?etween TPS III and other samples were also calculated from which they can be easily and rapidly discriminated. Vectorial angle method provide a potential method for quality control of TPS from green tea.The effects of TPS I, TPS II and TPS III were tested on hyperglycemic diabetic mice. The influence on the fasting blood glucose (FBG) level, glucosylated serum protein (GSP) level and Maleic Dialdehyde (MDA) level in the alloxan-induced diabetic mice among TPS I, TPS II and TPS III are monitored. Results indicated that TPS I, TPS II and TPS III could significantly decrease fasting blood glucose (FBG) and glucosylated serum protein (GSP) in alloxan-induced diabetic mice compared to the control group. Glucose tolerance curves of alloxan-induced diabetic mice treated with TPS I, TPS II and of TPS III were significantly shifted downwards after 14 days treatment. TPS II at the dose of 800 mg/kg.d and TPS I at the dose of 400 mg/kg.d had great preventive effect on hyperglycemia in mice. Taken together, the results indicate that a soluble tea polysaccharide, arabinogalactan proteins, is the major hypoglycemic factor in tea.In vitro antioxidant activities of TPS I, TPS II and TPS III for scavenging hydroxyl radicals and superoxide radicals decreased with the degree of purification, and were lowest for the TPS III.Preventive effects and decreasing effects of TPS I, TPS II and TPS III on hyperlipidemia in rats were investigated. Several important parameters in serum such as triacylglycerol (TG), cholesterol (TC), HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C)were assayed. The results showed that that TG, HDL-C, LDL-C in treatment groups was not significantly affected by TPS from green tea compared with those of control. The data of TC indicated that TPS III had alleviative effect on hypercholesterolmia in rats. The results also showed that TPS III can enhance the antioxidant activity in hypercholesterolmic rats. Three TPS production with different purities had influence on the serum magnesium, copper and zinc in hyperlipidemic rats, which indicated that TPS from green tea might regulate the hyperlipidemia in rats.The effect of TPS I, TPS II and TPS III on the healthy liver cell HL-7702 and the anti-tumor activity on the liver cell SMMC-7721. TPS II was found to be effective on inhibiting SMMC-7721 and does not affect the growth of healthy liver cell HL-7702. TPS I was found to inhibit not only the growth of the tumor cell SMMC-7721 but also the growth of healthy liver cell HL-7702. The inhibitive ratio of TPS III on the growth of tumor cell SMMC-7721 is low.The article indicates that this polysaccharide may be developed to a potential natural hypoglycemic, and hypercholesterolmic functional ingredient.
|
PDF Full Text Request