Tea flavonoids and their effect on chronic inflammation induced in Trypanosoma brucei brucei infected mice

Abstract

Emerging scientific data from pharmacological and physiological studies continue to show that tea has beneficial effects on human health by boosting immunity. In vitro studies have shown that flavonoids help immune response by acting as anti-cancer, anti-viral and antibacterial agents. In this study, different types of commercial tea samples were assayed for their phenolic composition, antioxidant activity and their effect on chronic inflammation induced by Trypanosoma brucei brucei in mice. High performance liquid chromatography was used for the identification and quantification of catechins. Subsequently, total phenolic content was determined spectrophotometrically using Folins-ciocalteus method. Total theaflavins and thearubigins were also determined. The radical scavenging behavior of the polyphenols on 2, 2- diphenyl-1-picrylhydrazyl radical (DPPH) was also studied spectrophotometrically. Total polyphenols, total catechins and antioxidant activity were significantly (P<0.05) different in the tea samples. Green tea had the highest levels of catechins, total polyphenols and total antioxidant activity. White tea was not significantly different from green tea. Epigallocatechin gallate (EGCG) was the most potent catechin and the most potent in antioxidant activity (r=0.989 ***). Black tea contained high levels of theaflavins and thearubigins, which accounted for most its antioxidant potential (r=0.930*** and r=0.930***, respectively). Gallic acid (GA) also showed significant(r=0.530*) contribution to the antioxidant activity in black tea. Green, black and white tea products processed from Kenyan tea cultivars originally selected for black tea had significantly (P<0.05) higher antioxidant activity than green tea processed from tea cultivars from Japan and China. These seem to suggest that the cultivar type is critical in determining the antioxidant potency of tea product and that black teas processed from suitable cultivars could be potent in antioxidant activity when compared to green teas. In vivo study was carried out to determine the effect of tea on an animal model of Swiss albino mice infected with Trypanosoma brucei brucei isolate KETRI 2710. The purity and trueness to type of the isolate was screened using polymerase chain reaction (PCR). The isolate produced a similar clinical picture after a pre-patent period of 5 days post infection (DPI). The levels of parasitemia in the control infected mice and those given different teas developed exponentially at similar rates reaching a peak on 7 DPI. However, the decline on 9 to 13 DPI was significantly (P<0.05) different with that of treated mice decreasing more rapidly. This demonstrated that tea lowered parasitemia level, which can be attributed to the trypanolytic effect of tea flavonoids. A fall in erythrocyte packed cell volume (PCV) occurred within 4 DPI due to hemolysis of erythrocytes and consequent anaemia by trypanosomes. A significant difference (P<0.05) was observed on 11 DPI between the infected mice given tea and the infected untreated mice. Thus tea enhanced resistance to erythrocyte hemolysis signifying it could have a therapeutic role in cases of anaemia. The effect of tea on acute phase response and chronic inflammation was observed because tea produced a significant (P<0.01) elevation of parasite-induced hypoalbuminemia as compared to the infected untreated mice. The same effect was observed in the pathology of liver sections where tea reduced periportal and parenchymal infiltration and the resulting karyohexis and karyolysis compared to the infected untreated animals. Additionally tea showed a significant (P<0.05) effect on the survival rate between the infected untreated mice and those given tea. Although green and white teas were superior in most of these characteristics, black tea, which is the principle tea product from Kenya, displayed remarkable properties some even comparable to those of green tea. Tea was more efficacious than an anti-inflammatory drug (dexamethasone), demonstrating its potential as a therapeutic agent.