Abstract
Isohemigossypolone (1) and 2-O-methylisohemigossypolone (2), major fungitoxins of Pachira aquatica, were found to accumulate locally in the outer bark of the swollen trunk, whereas the inner bark and heartwood contained only a trace amount of them. From P. aquatica that was infected with a phytopathogenic bacterium, we detected significant amounts of 1 and 2 from browned inner tissues of the swollen trunk. According to a quantitative analysis by a gas-chromatograph, the concentration of 1 in the diseased inner tissues was calculated to be approximately 780 μg/g f.w., which was the same level as that in the outer bark of healthy individuals. These findings suggest that the inner tissues inducibly produced and accumulated antifungals 1 and 2 during infection events, as do many plants with phytoalexins. 11-Nor-2-O-methylisohemigossypolone (3), showing approximately equivalent fungitoxic activity to that of 1 and 2, was also isolated from the infected inner tissues. We screened pathogenic bacteria from the infected tissue, and isolated a rod-shaped bacterium that was tentatively identified as Pseudomonas sp. which promoted tissue-browning on sectioned disks of P. aquatica trunks.
