Enniatins are cyclohexadepsipeptides commonly isolated from fungi and are known to have antibiotic properties. Many act as ionophores, forming pores in cellular membranes to allow selective ion transport. Enniatin B1 is one of four major analogs of the enniatin complex . It has been shown to induce apoptosis in several cancer lines (EC50s ≤ 10 μM) and to decrease the activation of the cell proliferation kinase, ERK (p44/p42). Enniatin B1 also inhibits the multi-drug resistance transporter Pdr5p from S. cerevisiae and has been used to examine drug resistance mechanisms.