Concentrated Extract of Green Tea Polyphenols Enhances the Toxicity of the Elderberry Lectin Nigrin b to Mice

Green tea contains polyphenols, which include flavanols, flavandiols, flavonoids, and phenolic acids. And most of the green tea polyphenols (GTPs) are flavonols, commonly known as catechins. Some studies have shown that GTPs are a source of valuable phytochemical compounds whose consumption may improve health and constitute a protection factor against some pathologies, especially cardiovascular disorders and cancer. However, the effect of the administration of large amounts of green tea polyphenols is a matter of controversy.

In this study, the authors explored whether a polyphenol mixture from a concentrated green tea extract (Polyphenon 60) could alter the effects on mice of the type 2 (two chains) ribosome-inactivating protein nigrin b isolated from Sambucus nigra L. Polyphenon 60 preparation was obtained from Sigma-Aldrich Química S.A. Highly purified nigrin b was prepared from elderberry bark by the affinity chromatography procedure to ensure the maximal activity. 28 Swiss female mice (6 weeks old; 28 - 30 g body weight) obtained from the university facilities were housed individually in plastic cages and fed (V1535-000 Ssniff Specialdiäten GmbH) ad libitum with free access to water under a 12 h light-dark cycle.

The results indicated that independent administration to mice of 30 mg/kg body weight of Polyphenon 60 by oral gavage or 10 mg/kg body weight of nigrin b administered via the intraperitoneal route (i.p.) did not affect survival. In contrast, the simultaneous treatment greatly enhanced nigrin b toxicity leading to the death of some animals. The histological analysis revealed that the most serious injury was inflicted on the small intestine crypts, which disappeared, and on the liver, which evidenced hepatotoxicity showing haemorrhagic areas.

In conclusion, these findings would prove useful for cancer therapy research that uses polyphenols as driving therapeutic drugs or as adjuvant supporting conventional therapy and also raise concerns on the use and abuse of concentrated green tea extracts as a food antioxidant supplement, in particular when a simultaneous toxin-driven tissue derangement occurs.

Article by Pilar Jiménez, et al, from Spain.

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