Verticilide, a new ryanodine-binding inhibitor, produced by Verticillium sp. FKI-1033

A new ryanodine-binding inhibitor, verticilide, was isolated from the cultured broth of a fungus, Verticillium sp. FKI-1033. It is a 24-membered ring cyclic depsipeptide, its structure being elucidated as cyclo[(2 R )-2-hydroxyheptanoyl- N -methyl- L -alanyl] 4 . Verticilide inhibited ryanodine binding to ryanodine receptors in the cockroach at an IC 50 value of 4.2 μ M , whereas inhibition against mouse ryanodine receptors was weak (IC 50 =53.9 μ M ).