Water extracts of green tea

Recently, research on the biomedical activity of pu-erh tea has focused on its antibacterial, antioxidative, lipid-lowering, and antiobesity effects. Many in vitro studies have shown that pn-erh tea has antioxidative activity. Lin et al. reported that the water extract of pn-erh tea (100 pg/ml) can protect the plasmid DNA from strand breakage indnced by the Fenton reaction as well as the control, regardless of total catechin content. Dnh et al reported that pn-erh tea water extract with less cat-echins (8.01 mg/ml), compared to green tea water extract with more catechins (79.1 mg/ml), could still chelate metal ions, scavenge DPPH radicals, and decrease nitric oxide production in lipopolysaccharide-activated RAW 264.7 macrophages. 

Figure 20.4.18. Recovery (mass extracted / mass in natural matter x 100) of (a) alkaloids and (b) eateehins in the PLE of green tea leaves using ( ) water or ( ) ethyl lactate.

The total antioxidant activity of teas and tea polyphenols in aqueous phase oxidation reactions has been deterrnined using an assay based on oxidation of 2,2 -azinobis-(3-ethylbenzothiazoline-sulfonate) (ABTS) by peroxyl radicals (114—117). Black and green tea extracts (2500 ppm) were found to be 8—12 times more effective antioxidants than a 1-mAf solution of the water-soluble form of vitamin E, Trolox. The most potent antioxidants of the tea flavonoids were found to be epicatechin gallate and epigallocatechin gallate. A 1-mAf solution of these flavanols were found respectively to be 4.9 and 4.8 times more potent than a 1-mAf solution of Trolox in scavenging an ABT radical cation. 

Decaffeination of Coffee and Tea This application is driven by the environmental acceptability and nontoxicity of CO2 as well as by the ability to tailor the extraction with the adjustable solvent strength. It has been practiced industrially for more than two decades. Caffeine may be extracted from green coffee beans, and the aroma is developed later by roasting. Various methods have been proposed for recovery of the caffeine, including washing with water and adsorption. 

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