METABOLISM OF THE PESTICIDE METABOLITE 4-[U-C-14] NITROPHENOL IN DATURA-STRAMONIUM (L) CELL-SUSPENSION CULTURE - A MODEL FOR PROCESSING OF XENOBIOTIC CARBOHYDRATE CONJUGATES AND FORMATION OF NONEXTRACTABLE RESIDUES

The biotransformation of the pesticide metabolite 4[U-C-14]nitrophenol was studied in cell suspension cultures of Datura stramonium (L.), wh ich were routinely subcultured every 9 or 10 days. In a standard metab olism experiment (48 hr of incubation) starting 7 days after subcultiv ation, the xenobiotic was found conjugated to its beta-glucoside (ca. 22% of applied C-14) and gentiobioside, Glc-beta(1-->6)-Glc-beta-4-nit rophenol (ca. 64%); about 7% of the parent remained unchanged. The con jugates were identified using TLC, HPLC, and their UV spectra. In cont rast to previous, analogous studies with carrot, soybean, and wheat, a greater portion of nonextractable residues (11.2%) was detected. A ti me-course study (started 6 days after subcultivation for 96 hr) demons trated that the disaccharide was formed from Glc-beta-4-nitrophenol, a nd that the major percentage of bound residues (7.1 of 12.2%) emerged in the last 72 hr of incubation. The data suggested this portion was d ue to a turnover of 4-nitrophenol conjugates. Two time-course experime nts started directly after subcultivation and performed for 10 and 16 days confined that this turnover was confined to late rapid growth and stationary phases of the culture cycle. The main metabolite Glc-beta( 1-->6)-Glc-beta-4-nitrophenol proved to be only a temporary product wh ich was degraded considerably (ca. 22%) during this period in favor of the beta-glucoside and nonextractable residues. According to these da ta, xenobiotic conjugates may be regarded as temporary storage product s subject to turnover in the plant, as reported frequently for those o f secondary compounds. The metabolic processes observed were attribute d to differentiation processes possibly occurring especially during th e stationary phase of the cell culture. In general, these are characte rized by initiation of structural organization and increased cell aggr egation and lignification and are known in particular for cell culture s of solanaceous species. (C) 1997 Academic Press.