Argadin, a new chitinase inhibitor, produced by Clonostachys sp. FO-7314

A new chitinase inhibitor, designated as argadin (1), was isolated from the cultured broth of a fungal strain FO-7314. The strain was identified as Clonostachys sp. from the morphological characteristics. Argadin was purified from the cultured mycelium by a combination of cation exchange, adsorption and gel filtration chromatographic methods. The structure of argadin was elucidated as cyclo(Nomega-acetyl-L-arginyl-D-prolyl-homoseryl-histidyl-L- 2-aminoadipyl) in which homoseryl gamma-methylene bonded to histidyl alpha-amino residue. The IC50 value of argadin against Lucilia cuprina (blowfly) chitinase was 150 nM at 37 degrees C and 3.4 nM at 20 degrees C. Argadin arrested the moult of cockroach larvae upon injection into the ventral abdominal part.