Doxorubicin is a very effective antitumour agent used in the treatment of various solid tumours. Apart from common side-effects in anticancer therapy, such as bone marrow suppression, nausea and vomiting, its clinical use is largely limited by the occurrence of a cumulative dose-related cardiotoxicity, which manifests itself as congestive heart failure. This observed cardiotoxicity is believed to be mainly caused by free (oxygen) radicals.

Flavonoids are a class of naturally occurring compounds, which are abundantly present in vegetables, fruits and beverages such as tea and red wine. Besides their relevance in plants, they are pharmacologically important for man, because of their high pharmacological potency. They are major ingredients of many traditional medicines and several health claims have been ascribed to flavonoids. In vivo experiments showed a dose dependent protection by the flavonoid monoHER. Using telemetry, changes in the ECG were recorded to monitor the cardiotoxicity. Transmitters were implanted into the peritoneal cavity of male Balb/c mice (20-25 g). The leads were placed subcutaneously. A possible increase in ST-interval in the ECG could be detected at an early stage as the animals were monitored during treatment.

Flavonoids have been shown to participate in several different mechanisms such as binding to enzymes and cell membranes and electron transfer in enzyme systems. The properties however, which are probably most promising for the use of flavonoids as modulators of doxorubin-induced toxicity are their radical scavenging and iron chelating properties. A drawback of monoHER therapy is the relatively high dose of 500 mg/kg needed to obtain complete protection. Therefore, current research is emphasizing on the development of new compounds with improved antioxidant properties and increased selectivity. The goal is to obtain more potent compounds than monoHER, that can be administered in lower doses.