Growth Inhibitor of insect larvae from Paulownia tomentosa

Paulownia (Paulownia tomentosa (Thumb.) Sieb. & Zucc. ex Steud.) has been used as a traditional medicine for stomach disease in China. In Japan, it is called 'Kiri', which is often used as the material of chests of drawers. When paulownia is used industrially, a lot of sawdust is generated. From sawdust of paulownia, we isolated the paulownin as a major compound and some paulownin derivatives, and examined the growth inhibition of insect larvae with MeOH extract and paulownin.

First, one with MeOH extract treatment (2.5, 5.0, and 10.0mg/mL), one with paulownin treatment (2.5, 5.0, and 10.0mg/mL), and a control group were prepared. We measured the instars of larvae every week for 3 weeks after MeOH extract and paulownin were added in nutrient medium, and the head width of each larva was measured after three weeks. The results showed instars of larvae were delayed and head diameters of larvae were smaller for MeOH extract and paulownin treatment groups in comparison with control. In conclusion, we proved that sawdust of paulownia has a protecting effect against insects.