Isolation of a bioactive substance from the silkworm (Bombyx mori Linnaeus) that accelerates the germination of the entomopathogenic fungus Nomuraea rileyi (Farlow) Samson.

The conidium of the entomopathogenic fungus Nomuraea rileyi has been found to germinate rapidly in the presence of host insect-derived extracts. Thus the extract appears to contain an important factor involved in host recognition by N. rileyi. However, the substance responsible for such unique germination behavior has yet to be identified. Hence we attempted to purify this substance. One thousand g of dried silkworm pupae was subjected to methanol extraction, followed by methanolysis, two different solvent partitions, and three different column chromatographies. A total of 12.4 mg of substance was obtained in the active fraction. The substance obtained exhibited an activity more than 46,000 times higher than that of the methanol extract. The substance was detected as a single peak on Sephadex LH20 column chromatography and as a single band on high-performance thin-layer chromatography. These data indicate that the concentrated fraction contained a high-purity substance.