Cardioprotective effects of Viscum album L. subsp. album (European misletoe) leaf extracts in myocardial ischemia and reperfusion.

ETHNOPHARMACOLOGICAL RELEVANCE: Viscum album L. (European mistletoe) is a hemiparasitic plant belonging to Loranthaceae family and has been used in Turkish traditional medicine for the treatment of cardiovascular disorders and heart diseases such as hypertension, tachycardia and angina pectoris.

AIM OF THE STUDY: The present study investigated the cardioprotective effects of V. album leaf extracts in myocardial ischemia and reperfusion injury in rats.

MATERIAL AND METHODS: Lyophilized aqueous (AVa) and methanolic (MVa) extracts of V. album were prepared from dried leaf. The isolated hearts were perfused with V. album extracts prior to and during 35min of ischemia induced by coronary artery occlusion. After 120min of coronary reperfusion, infarct size was determined by triphenyltetrazolium staining.

RESULTS: Both AVa and MVa extracts reduced the extent of infarction compared with untreated control hearts, but protective effect of MVa had more potential in low concentration; infarct size as proportion of ischemic risk zone: AVa 17.5±1.5%; Mva 20.3±2.5%, both P<0.01 versus control 38.1±1.4%. This protective effect was comparable to infarct limitation induced by ischemic preconditioning (21.5±2.4%). Inhibition of nitric oxide synthesis with L-NG -nitroarginine methyl ester completely abrogated the protection afforded by both extracts. ATP-sensitive K+ channel blockade by glibenclamide abrogated the protection afforded by MVa while attenuating, but not abolishing, the protective action of Ava.

CONCLUSIONS: This study provided the first experimental evidence that V. album leaf extracts can mediate nitric oxide-dependent cardioprotection against myocardial injury produced by ischemia/reperfusion insult. With this study, popular usage of V. album extracts in Turkish folk medicine as a remedy for cardiac diseases was justified.