NAPHTHOQUINONE BIOSYNTHESIS IN HIGHER PLANTS: I. STUDIES ON 2-HYDROXY-l,4-NAPHTHOQUINONE IN IMPATIENS BALSAMINA L.

The biosynthesis of 2-hydroxy-1,4-naphthoquinone in aerial portions of Impatiens balsamina L. (Balsaminaceae) has been studied. Phenylalanine-U-14C and sodium acetate-1-14C did not label the quinone. Shikimic acid-U-14C, however, was incorporated into the quinone with a dilution of 15.7. The conversion of shikimic acid to ferulic acid in these experiments was accomplished with a dilution of 39.6. GIucose-U-14C was incorporated into the naphthoquinone and ferulic acid molecules with dilutions of 9230 and 29,500 respectively. Administration of an excess of cold p-hydroxybenzoic acid along with labeled shikimic acid resulted in no incorporation of label into the quinone. Degradation of labeled 2-hydroxy-1,4-naphthoquinone yielded phthalic acid with 68.5% of the label originally in the quinone. This agrees well with the theoretical value of 67% calculated on the basis that the shikimic acid ring is incorporated intact into the quinone ring of 2-hydroxy-1,4-naphthoquinone.