Mechanism of antifeedant activity of plumbagin, a compound concerning the chemical defense in carnivorous plant

Dionaea muscipula Ellis accumulates a large amount of plumbagin (1), which operates as an antifeedant against predators. Content of 1 reached 0.5% weight of the fresh trap lobes. It was found that other carnivorous plants also accumulated similar naphthoquinone-type strong antifeedant. Thus, naphthoquinone analogs are widely used as an antifeedant among the carnivorous plants. By using several analogs of 1, we clarified that both the high volatility and high redox potential of 1 are important for its strong antifeedant activity. It was known that plumbagin stimulates the mitochondrial electron transport system as a result of intercepting electrons. These results suggested that the Droseraceae family possesses a universal defensive mechanism against predators, that is, accumulation of volatile naphthoquinone with high redox potential as defensive substance. Thus, it is estimated that highly volatile naphthoquinone of moderately high redox potential would be used as an antifeedant of weak toxicity.