Oh

R = II Quercetin

R = Sugar Quercetin-3-0-moDoglyco3ide

Figure 4 Chemical structure of the flavonoids.

Macromolecular Compounds

Macromolecular components of acellular extracts analysed by electrophoresis show a complex protein pattern ranging from 14 to 90 kDa in molecular weight, quite distinct from the one obtained with V. album (Fernández et al., 1998). When extracts are analysed under denaturing and reducing conditions and transferred onto nitro-cellulose, mouse anti-Ligaria antiserum reacts not only with acellular extracts of L. cuneifolia, but also with those of V. album and other Viscaceae species such as Ph. liga, thus demonstrating that the proteins present in the above species exhibit antigenically related epitopes (Wagner et al., 1998).

BIOLOGICAL AND PHARMACOLOGICAL PROPERTIES Vasoactive Activity

Given its outward similarity to V. album, Argentine mistletoe (L. cuneifolia) is widely employed in infusions as an alternative medicine to treat high blood pressure (Domínguez, 1928; Ratera and Ratera, 1980). The first pharmacological and phytochemical studies performed on L. cuneifolia samples disclosed a degree of hypotensive action (Domínguez, 1928). Since extracts administered parenterally have been reported to exert experimental hypertension, indiscriminate use should be guarded against (Domínguez, 1928; Ratera and Ratera, 1980).

It was Izquierdo and co-workers who originally demonstrated the presence of tyramine, a compound exerting sympathomimetic activity (Izquierdo et al. 1955).

Recent studies compare the cardiovascular effects of samples of L. cuneifolia growing on three host trees: Schinus polygamus (Cav.) Cabr. (Anacardiaceae), Acacia caven (Mol.) Molina (Mimosaceae) and G. decorticans (Taira et al., 1994). The specimen growing on S. polygamus exerts a dose-dependent pressor effect (Figure 6) accompanied by a secondary hypotensor phase, whereas high doses produce a drop in heart rate. The fact that the a-adrenergic antagonist phenoxybenzamine inhibits the pressor action of

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