New hydroxylated metabolites of 4-monochlorobiphenyl in whole poplar plants

Two new monohydroxy metabolites of 4-monochlorobiphenyl (CB3) were positively identified using three newly synthesized monohydroxy compounds of CB3: 2-hydroxy-4-chlorobiphenyl (2OH-CB3), 3-hydroxy-4-chlorobiphenyl (3OH-CB3) and 4-hydroxy-3-chlorobiphenyl (4OH-CB2). New metabolites of CB3, including 2OH-CB3 and 3OH-CB3, were confirmed in whole poplars (Populus deltoides × nigra, DN34), a model plant in the application of phytoremediation. Furthermore, the concentrations and masses of 2OH-CB3 and 3OH-CB3 formed in various tissues of whole poplar plants and controls were measured. Results showed that 2OH-CB3 was the major product in these two OH-CB3s with chlorine and hydroxyl moieties in the same phenyl ring of CB3. Masses of 2OH-CB3 and 3OH-CB3 in tissues of whole poplar plants were much higher than those in the hydroponic solution, strongly indicating that the poplar plant itself metabolizes CB3 to both 2OH-CB3 and 3OH-CB3. The total yield of 2OH-CB3 and 3OH-CB3, with chlorine and hydroxyl in the same phenyl ring of CB3, was less than that of three previously found OH-CB3s with chlorine and hydroxyl in the opposite phenyl rings of CB3 (2'OH-CB3, 3'OH-CB3, and 4'OH-CB3). Finally, these two newly detected OH-CB3s from CB3 in this work also suggests that the metabolic pathway was via epoxide intermediates. These five OH-CB3s clearly showed the complete metabolism profile from CB3 to monohydroxylated CB3. More importantly, it's the first report and confirmation of 2OH-CB3 and 3OH-CB3 (new metabolites of CB3) in a living organism

Halide effects in the hydrolysis reactions of (±)-7β,8α-dihydroxy- 9α, 10α-epoxy-7,8,9,10-tetrahydrobenzo-[α]pyrene

Rates of reaction of (±)-7β,8α-dihydroxy-9α,10α-epoxy-7,8,9,10- tetrahydrobenzo[α]pyrene (DE-2) have been determined in 1:9 dioxane-water solutions containing 1.0 M KC1, 0.5 M KBr, and 0.1 M NaI over the pH range 4- 13. These pH-rate profiles are more complicated than those for reaction of DE-2 in 0.2 M NaC1O4 solutions and are interpreted in part by mechanisms in which halide ion attacks the diol epoxide as a nucleophile at intermediate pH, resulting in the formation of a trans-halohydrin. Reaction of DE-2 in these halide solutions at pH 12, the rate of reaction of DE-2 increases due to a second- order reaction of HO- with DE-2.link_to_subscribed_fulltex

Quantitative aspects of the effects of halide and azide ions on the acid-catalyzed hydrolysis of (±)-7β,8α-dihydroxy-9α,10α-epoxy-7,8,9,10- tetrahydrobenzo[a]pyrene

Mechanisms of the acid-catalyzed reactions of (±)-7β,8α-dihydroxy-9α,10α-epoxy-7,8,9,10- tetrahydrobenzo[a]pyrene (1) in 1:9 dioxane-water solutions containing varying concentrations of KCl, KBr, NaI, NaN3 and NaClO4 are discussed.link_to_subscribed_fulltex

Change of rate limiting step in general acid-catalyzed benzo[a]pyrene diol epoxide hydrolysis

The rates of reaction of (±)-7β,8α-Dihydroxy-9α,10α-epoxy-7,8,9,10- tetrahydrobenzo[a]pyrene (1) in 1:9 dioxane-water buffer solutions containing primary amines whose pK(a) values span the range of 5.410.7 have been determined. For those amines with pK(a) values ca. 8, both acid and base forms of the buffer react with 1. The magnitude of the kinetic term in the base form of the amine (RNH2) increases with amine pK(a) and is attributed to nucleophilic addition of the amine to the epoxide group. Curvatures in plots of the kinetic term due to buffer (k(buff)) as a function of the mole fraction of buffer acid for substituted ammonium ions with pK(a) > 8 are interpreted in terms of a change in rate-limiting step of the general acid-catalyzed pathway from epoxide ring opening at low amine base concentrations to reaction of amine base acting as either a general base or nucleophile with an α-hydroxycarbocation at higher amine base concentrations. Thus, epoxide ring opening of I in buffer solutions of the more basic amines is a reversible reaction. Rate and product studies of the reaction of 1 in acid solutions (pH 5.5) and in Tris buffer solutions containing sodium azide show that azide ion is effective in trapping the α- hydroxycarbocation intermediate, subsequent to its rate-limiting formation by reaction of 1 with either H+ or Tris-H+. These results demonstrate that the intermediate formed from epoxide ring opening of 1 with acids has a sufficient lifetime so that its reaction with azide ion competes with its reaction with solvent.link_to_subscribed_fulltex