Study on biodegradation of aromatic compounds by liverwort cultured cells toward bioremediation

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The liverworts and their cultured cells biosynthesized highly oxygenated secondary metabolites. We examined the production of highly oxygenated terpenoids and their biosynthetic pathways to verify oxidative degradation capacity of chemicals. An endocrine-disturbing chemical, bisphenol A (BPA) was examined to be metabolized by cultured cells of the liverworts. The following results were obtained.The biosynthesis of oxygenated cuparenes, (-)-2-cuparenol, (-)-2,3-dihydroxycuparene and (-)2,5-cuparenoquinone, has been studied by feeding [2^<-13>C]-, [4^<-13>C]-, [4^<-2>H_2]-, [4^<-2>H_2, 4^<-13>C]-and [5^<-2>H_2, 5^<-13>C]mevalonate (MVA) to cultured liverwort cells, Lejeunea aquatica, followed by ^2H and ^<13>C NMR analysis of the resultant ^2H and ^<13>C labeled compounds. The labeling patterns indicate a stereoselective cyclization of a bisabolyl cation to a cuparenyl cation, and provide evidence for the simultaneous involvement of 1,4-and double 1,3-hydride shifts in the formation of c … More uparene from a cuparenyl cation and hydroxylation to the aromatic ring of cuparene with an NIH shift to generate 2-cuparenol and 2,3-dihydroxycuparene. The NIH shift was also confirmed in the formation of 2,5-cuparenoquinone.One novel labdane-type diterpene, named ptychantin O and two known diterpenes, ptychantin G and F have been isolated from cultured cells of the liverworts, Ptychanthus striatus, and their structures were determined by NMR analyzes.Degradation of BPA, 2,2-bis(4-hydroxyphenyl)propane, an endocrine disturbing chemical, by the cultured cells of liverworts, P.striatus and Heteroscyphus planus, was examined. About 95% of BPA initially present (0.12 mM) decreased in 5 days of culture of these liverwort cells. BPA was degraded to-4-propenylphenol,4-propylphenol,4-hydroxyacetophenone,4-isopropyl-2-hydroxyphenol, and also was biotransformed to 4,4'-isopropilidenediphenol-O-β-D-(6"-O-methyl)-glucopyranoside. Biodegradation mechanism of BPA was also examined by feeding [^2H_<14>]-BPA. The degradation products of BPA were assumed to be formed by the one-electron oxidation of the substrate by extracellular peroxidases. Less