Protective Activity of Polyphenon E Against Liver Protein Oxidation in Rats after Mnu I.P. Administration

Sanda ANDREI, Adela PINTEA, Dumitrita RUGINA, Cristina STEFANUT, Andrea BUNEA, Florin A. GAL


Many studies demonstrated the direct relation between the reactive oxygen specieis (ROS) accumulation, the oxidative stress, and the cancer development. Also, it has been shown that a large number of naturally occurring compounds from vegetables and fruits are effective as chemopreventive agents. For example, Polyphenon E is a highly purified tea catechin extract with antioxidant, immunomodulatory and antimetastatic properties. In the present experiment we have studied the protective effect of a mixture of green tea catechins, Polyphenon-E (Poly E) on induced oxidative degradation of proteins in rats liver i.p. injected with N-Methyl-N-nitrosourea (MNU). Rats were divided into 4 groups: group 1 controls (n=5); group 2 and 4 rats inoculated with MNU (n=10/group). A freshly prepared green tea solution of 0.5% Poly E in tap water was supplied every days to experimental animals from group 3 and 4 (n=10/group). Liver samples of all rats were collected and protein extracts were analyzed for total protein content and protein oxidation, using a Protein Assay Kit Bio-Rad (based on Bradford’s method) and derivatisation of the carbonyl group with 2.4-dinitrophenylhydrazine (DNPH) for carbonylated proteins (results were expressed in g of proteins per 1 g tissue and nmoles DNPH per mg of protein). Total proteins content in the liver did not change significantly by the administration of Poly E (average of 0.129 ± 0.0094 for the control group, 0.127 ± 0.027 respectively for the group supplemented with PolyE).Intraperitoneally administration of MNU cause a slight decrease in protein content (0.129 ± 0.0094 for the control group, respectively 0.112 ± 0.031 for group 2) and a significant increase in hepatic protein oxidation levels in group 2 compared with the control group 1 (0.745 ± 0.17 mmole, respectively 0.457 ± 0.10 mmol). It was also observed protective effects of Poly E (0.745 ± 0.17 nmol for the group injected with MNU, respectively 0.626 ± 0.13 nmol for the group injected with MNU and supplemented with PolyE). In the present research work, we demonstrated that polyphenon-E can act as an antioxidant agent and protects liver proteins.


protein oxidation, liver, polyphenon E , N-Methyl-N-nitrosourea

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