The juice of the banana trunk produces a non-depolarising neuromuscular block. Oxygenation of the extract enhances its potency. Reversals with anticholinesterases are transient. Partial reversals in isolated preparations indicate these could be both specific and non-specific binding which could account for blockade after washing. It could be specifically bound to ACh receptors in an irreversible way since its action appears similar to that of alpha-BuTX.