Phoratoxins are a group of peptide toxins that belong to the family of thionins, a subdivision of small plant toxins (5000 kD MW).[1] Phoratoxins are proteins present in the leaves and branches of the Phoradendron, commonly known as the American variant of the mistletoe, a plant commonly used as decoration during the festive season. The berries of the mistletoe do not contain phoratoxins, making them less toxic compared to other parts of the plant. The toxicity of the mistletoe is dependent on the host tree, since mistletoe is known to be a semi-parasite. The host tree provides fixed inorganic nitrogen compounds necessary for the mistletoe to synthesize phoratoxins.[2]
Viscotoxins are similar plant thionins produced from the leaves and stems of the European mistletoe (Viscum album).[3]