> Black walnut (Juglans nigra L.) produces juglone (5
> hydroxy-1,4-napthoquinone), an allelopathic chemical
> present in all its parts which is a respiration
> inhibitor that deprives sensitive plants of energy for
> metabolic activity.
I did a literature search in Agricola and Bioabstracts. Juglone is
generally cytotoxic, inhibiting glycolysis and many enzymes, but it's
biggest effect is as a redox cycling agent like paraquat. It interacts with
respiratory quinones producing superoxide, depleting antioxidants and
damaging mitochondria. It is not persistent in the soil. It is mutagenic,
carcinogenic in certain contexts, and poisonous to fish. It has been
rejected as an anticancer agent because it is too generally toxic. I
couldn't tell from the literature how well absorbed it is from the digestive
track of mammals, although some work has been done on absorption from the
insect gut, where pH is an important factor. Many otherwise toxic phenolic
plant metabolites bind to proteins and pass out of the body in feces (I
don't know specifically about juglone). It wouldn't surprise me if juglone
can kill intestinal parasites.
Dale Wilson
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