Mistletoe grows on several types of trees, and the chemical composition of extracts derived from it depends on the species of the host tree (e.g., apple, elm, oak, pine, poplar, and spruce), the time of year harvested, how the extracts are prepared, and the commercial producer.[46,47] Reviewed in [8,36,48,49]
Mistletoe extracts are prepared as aqueous solutions or solutions of water and alcohol, and they can be fermented or unfermented.[6,46] Reviewed in [4,20,47,50,51,52,53] Some extracts are prepared according to homeopathic principles, and others are not. Accordingly, as homeopathic preparations, they are typically not chemically standardized extracts. Reviewed in [10,54] In addition, the commercial products can be subdivided according to the species of host tree, which is typically indicated in the product name by a suffix letter. Iscador, a fermented aqueous extract of Viscum album L. that is prepared as a homeopathic drug, is marketed as IscadorM (from apple trees; Malus domestica), IscadorP (from pine trees; Pinus sylvestris), IscadorQ (from oak trees; Quercus robur), and IscadorU (from elm trees; Ulmus minor). Helixor, an unfermented aqueous extract of Viscum album L. that is standardized by its biological effect on human leukemia cells in vitro, is marketed as HelixorA (from spruce trees; Picea abies), HelixorM (from apple trees), and HelixorP (from pine trees; Pinus sylvestris). Reviewed in  Eurixor, an unfermented aqueous extract of Viscum album L. harvested from poplar trees, is reportedly standardized to contain a specific amount of one of mistletoe's lectins (i.e., the lectin ML-1; refer to the History section of this summary for more information). Reviewed in  Some proponents contend the choice of extract should depend on the type of tumor and the gender of the patient. Reviewed in [49,51,56]
A recombinant ML-1 from Escherichia coli bacteria known as rViscumin or aviscumine has been studied in the laboratory and in phase I clinical trials. Since this is not an extract of mistletoe, it is out of the purview of this summary.