Naphthoquinones from Diospyros hebecarpa

Diospyros hebecarpa A. Cunn. is a small or medium tree which is common on the tropical coast of Queensland and has been suspected of poisoning livestock1. As other Diospyros species are reported to contain plumbagin2, it seemed possible that this is the toxic substance in D. hebecarpa. We have found that plumbagin is present in the leaves and bark of this species, and in addition we have isolated from the fresh leaves and immature fruits a new colourless crystalline compound, melting point 112−113° C., with the composition C11H10O3. In chemical properties and absorption spectrum this substance closely resembles β-hydrojuglone and β-hydroplumbagin, which are also colourless when pure. On oxidation with ferric chloride it gives a quinone, melting point 125–126° C. (‘Pyrex’), which is an isomer of plumbagin. (This quinone melts with decomposition at a much lower temperature in soda glass. Juglone behaves similarly, and its melting point may be raised to 164–165° C. in ‘Pyrex’ glass.)