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[(2R)-2-hydroxyheptanoyl-N-methyl- L-alanyl]4. Verticilide inhibited ryanodine binding to ryanodine receptors in the cockroach at an IC50 value of 4.2 μM, whereas inhibition against mouse ryanodine receptors was weak (IC50=53.9 μM).