Comparative Study on the Conformation of Phalloidin, Viroisin, and Related Derivatives in Aqueous Solution

We investigated the conformations of toxic phalloidin and viroisin in aqueous solution using 500–MHz 1 H‐NMR spectroscopy in conjunction with molecular modeling. The conformations of two non‐toxic phalloidin derivatives, secophalloidin and dethiophalloidin, were also correspondingly studied for comparison purposes. Results indicate that the non‐toxic peptides have a multiple conformation, whereas the toxic peptides are comprised of a rigid molecule. It was found that the conformation of phalloidin partially resembles that of viroisin in the region of Cys3‐Pro4‐Ala5‐Trp6, being different from that of the non‐toxic peptides; thereby suggesting this region plays an important role leading to their toxicity.