Comparative study concerning mistletoe viscotoxins antitumor activity

Viscum album L. (Santalaceae) (VA) - a parasitic plant that grows on various trees - has proved a significant anticancer effect in both experimental studies and clinical trials. The present study assesses the influence of oxidative stress in mistletoe induced cytotoxicity in tumor cells, in relation to classic cytostatic therapy. VA ethanolic extract was administered alone and combined with doxorubicin (chloride) in Swiss female mice previously intraperitoneally (i.p.) inoculated with Ehrlich tumor cells (1 × 106/animal) that consequently developed Ehrlich ascites carcinoma (EAC). The administered doses were of 50 mg/kg on the 1st, 3rd and 6th day for the VA extract, respectively of 2.5 mg/kg on the 1st and 6th day for doxorubicin, after tumor cell implantation. Fourteen days later all mice were euthanized, ascites of the EAC were collected in order to analyze the tumor proliferation parameters, as well as blood samples, in order to evaluate the antioxidant status in plasma. Tumor development was associated with increased activity of plasma enzymes; classic doxorubicin therapy not only prevents the accumulation of ascitic fluid, but also significantly reduces the activity of plasma antioxidant enzymes. Furthermore, in association with VA extract, the protective effect is improved. Oxidative changes in Ehrlich tumor cells consisted in decreased catalase activity and amplified xanthine oxidase and peroxidase activities.