HPLC analysis of the metabolized plumbagin. Samples were subjected to RP-C18 column chromatography that was run with a mixture of methanol/H2O (7:3, v/v). Compounds eluted were detected with UV absorbance at λ254. Samples were chloroform extract of: (A) the plumbagin-containing cultivation media of the wild-type E. coli; (B) the same preparation as (A) but with the ΔygfZ strain; (C) the same preparation as (A) but without bacteria; (D) synthesized 2,3-dimethyl-5-hydroxy-1,4-naphthoquinone extracted from media as described for (C). Compounds identification: I, plumbagin; II, 2,3-dimethyl-5-hydroxy-1,4-naphthoquinone; III, unidentified.