| Green tea extracts, which are biological activity, are rich in tea polyphenols, caffeine, aminophenol, saccharine and vitamins. This article studied the effect of water quality on nutritional components and antioxidant activity of green tea extracts for the first time. Also, this work researched the best method extracting the EGC-enriched extract and EGCG-enriched extract from green tea, discussed the contents of residual organic solvent prepared by solvent extraction.1 Effect of water quality on the nutritional components and antioxidant activity of green tea extractsGreen tea extracts (GTEs) were prepared with tap water (TW), activated carbon adsorbed water (AC), deionised water (DI), distilled water (DW), reverse osmosis water (RO) and ultra-pure water (UP). Their nutritional components were determined by chemical methods. Deoxyribose assay and xanthine oxidase method were applied to test the antioxidant activities of GTE in vitro. The results indicated that there was statistical significant difference (P < 0.05) in the yield rate, the contents of polyphenols, catechins, caffeine, copper, lead and fluorine. Among them, DI obtained the greatest yield rate and polyphenols with low caffeine, DW increased the contents of non-ester catechins and AC enhanced the concentrations of ester catechins. The contents of copper and lead in GTEs were highly correlated to those of the tested water (r = 0.767 and 0.871, respectively). Fluorine contents in all GTEs were higher than 6.0 g/Kg. GTE that prepared with RO displayed the highest antioxidant activities among the six GTEs.2 Optimization for the Extraction of EGC-enriched extract and EGCG-enriched extract from green teaThis study discussed the effect of extracting temperature, extracting time, solvent on extracting efficiency of EGC and EGCG from green tea by orthogonal design, analyzed the difference of catechin content and antioxidant activities of EGC and EGCG which were prepared by two-step extraction procedure. The results suggested that EGC was significantly affected by duration and solvent but not by extraction temperature, while EGCG was highly dependent of them with a efficiency order of extracting solvent > extracting temperature > duration (P<0.05) . The optimum condition for productivity of EGC was: green tea extracted with 75% ethanol at 30℃for 10 min. For productivity of EGCG was: green tea extracted with 35% ethanol at 90℃for 60 min. Furthermore, the research analyzed the distinction of catechin concentration and antioxidant activity (in Vitro) of EGC- or EGCG-enriched green tea extracts which were prepared by two-step extraction procedure. The results showed that the EGCG-enriched extract contained twice higher EGCG content and presented much higher antioxidant activity compared with EGC-enriched extract.3 Residual in Tea polyphenols, caffeine, and tea polysaccharides which extracted with organic solventA method for the determination of the contents of ethyl acetate in tea polyphenols, chloroform in caffeine, and chloroform and n-butanol in tea polysaccharides by SPME-GC was proposed. The operating conditions of SPME such as extraction temperature, extraction time were discussed. The results showed the best extraction temperature was 55℃and the extraction time was 15 min. The linear correlation coefficient was ethyl acetate 0.997, chloroform 0.994 and n-butanol 0.994. The results displayed that the content of ethyl acetate in the extract prepared by ion precipitation-ethyl acetate separation was 1847.44μg/g, that in the extract prepared by direct separation with ethyl acetate was 5.94μg/g; the content of chloroform in the extract prepared by direct separation with chloroform was 870.67μg/g, the content of chloroform and n-butanol in tea polysaccharides was 53.96μg/g and 80.95μg/g, respectively. |
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