Viscotoxin and lectin content in foliage and fruit of Viscum album L. on the main host trees of Hyrcanian forests

Mistletoe ( Viscum album L.) is a hemiparasitic plant that absorbs water and nutrients from the host tree. Mistletoe contains two groups of cytotoxic, immunomodulatory and antitumor proteins, viscotoxins and lectins. This study evaluated the quantity and quality of viscotoxins and total lectins in the stems with leaves (foliage) and fruit of mistletoe on Parrotia persica and Carpinus betulus in September with immature green berries and in December with mature white berries. Viscum album L. plants were harvested from host species located in the Hyrcanian forests of Iran in 2019. The highest level of viscotoxins was detected in the December foliage of V. album settled on C. betulus (9.25 mg/g dry weight [DW]), and the highest content of lectins was found in the December foliage of V. album settled on P. persic a (0.79 mg/g DW) and C. betulus (0.73 mg/g DW) respectively. The immature green berries of V. album from both host species contained much higher concentrations of viscotoxins and lectins than the mature white berries. Four isoforms of viscotoxins, viscotoxin A1, A2, A3 and B could be identified in all samples of both host species. Viscotoxin A3 was the predominant viscotoxin isoform followed by viscotoxin A1.