Formation and secretion of a unique quinone by hairy root cultures of Lithospermum erythrorhizon

Abstract A unique colorless quinone, named rhizonone, showing strong antifungal activity against spore germination of Cladosporium fulvum was isolated from the hairy root cultures of Lithospermum erythrorhizon in MS medium. The structure was elucidated as 5a-methyl-5a,6,10b,10c-tetrahydro-2H-anthra[9,1-bc]furan-7,10-dione mainly on the basis of spectroscopic data. This unique carbon skeleton, not previously known among the compounds isolated from this plant species, might be derived from geranylhydroquinone, an important intermediate of shikonin biosynthesis. Rhizonone was secreted into the medium while shikonin derivatives accumulated on the surface of the hairy roots and their debris.