TOXICITY AND METABOLISM OF 2,4-DICHLOROPHENOL BY THE AQUATIC ANGIOSPERM LEMNA-GIBBA

The toxicity and metabolism of 2,4-dichlorophenol, with regard to the aquatic macrophyte Lemna gibba (duckweed), have been studied. Toxicity is described in terms of the effect of 2,4-dichlorophenol (2,4-DCP) o n the vegetative reproduction of duckweed over a 10-d growth period; t he EC10 and EC50 were 2.5 and 9.2 mu M, respectively. Metabolism of 2, 4-dichlorophenol was monitored by incubation of the plants with radiol abeled substrate, and periodic sampling and analysis by reversed-phase HPLC of the plant growth medium. Depending on the growth conditions, up to 95% of the 2,4-DCP was metabolized over a 6-d growth period. To analyze the metabolites, the plants were grown in the presence of subl ethal concentrations of [U-C-14]-2,4-DCP. The growth medium was lyophi lized and then mixed with the plants, extracted, and analyzed using re versed-phase HPLC, followed by scintillation counting of the fractions . The major metabolite was isolated and identified as 2,4-dichlorophen yl-beta-D-glucopyranoside by high-field NMR and MS. The structure of t he metabolite was confirmed by synthesis and by enzymatic cleavage of the beta-glucosidic linkage to afford 2,4-DCP. An important consequenc e of conjugate formation is the masking of the presence of 2,4-DCP to the usual analytical techniques used for its detection and quantitatio n. This finding is probably applicable to other contaminants and organ isms.