The antibacterial activity of some naturally occurring 2,5-dihydroxy-1,4-benzoquinones

Polyporic acid, atromentin, bovinone, and oosporein are common metabolic products of a number of species of fungi. The related compound cochliodinol and its congeners are produced by several Chaetomium spp. These quinonoid metabolites have been shown to inhibit the growth and metabolism of a range of bacterial genera. The antibiotic activity of the quinones depends on the substituents at the 3 and 6 positions of the 2,5-dihydroxy-1,4-benzoquinone ring; in aerobic systems the activity appears to be inversely proportional to the polarity of the metabolite. It has been shown that reduction of the quinone to the hydroquinone changes the antibiotic activity of these metabolites but does not abolish it. Contrary to previous reports, the activity of these hydroquinones is not reversed by cysteine.