Senji Sakanaka

Preventive Effect of Green Tea Polyphenols against Dental Caries in Conventional Rats.

The effects of green tea polyphenols, inhibitors of various biological activities of cariogenic bacteria in vitro, on caries development were examined using conventional rats. A total of 96 male rats were divided into 8 groups and the rats in the test groups were given tea polyphenols ranging from 0.1% to 0.5% in their cariogenic diet or drinking water for 40 days. Total fissure caries lesions was significantly reduced by the addition of tea polyphenols to the diet or in the drinking water. Diet containing 0.1% tea polyphenols demonstrated about 40% reduction of total fissure caries lesions. No toxic effect of tea polyphenols on rats were observed under these experimental conditions.

Inhibitory effect of tannin in green tea on the proliferation of mesangial cells

The effect of green tea tannin on the proliferation of mesangial cells was determined in terms of [3H]thymidine uptake. When green tea tannin was added to the medium of mesangial cell cultures, it suppressed the proliferation of mesangial cells markedly. In particular, (-)-epigallocatechin 3-O-gallate, the predominant component of the green tea tannin mixture, exerted an inhibitory effect at a relatively low concentration, suggesting a direct corroboration of the renal effects.

Effect of Tannins in Green Tea on the Urinary Methylguanidine Excretion in Rats Indicating a Possible Radical Scavenging Action

The hydroxyl radical scavenging action of green tea tannin given orally to rats with experimental renal failure was examined by using the urinary methylguanidine excretion as an index. In rats given 2 mg of a green tea tannin mixture, the urinary methylguanidine excretion was significantly decreased or had a tendency to decrease. (-)-Epigallocatechin 3-O-gallate, the predominant component of the green tea tannin mixture, effected a decrease in the urinary methylguanidine excretion in rats at a dose as low as 0.25 mg, suggesting a hydroxyl radical scavenging action.