Problems with Paleocene Palynozones in the Rockies: Hell's Half Acre Revisited

The scheme of palynostratigraphic zonation most widely applied to interbasinal correlation of Paleocene rocks in the Rocky Mountain region of North America is fundamentally flawed. In its initial publication (based on juglandaceous fossil pollen), basic principles of biostratigraphy were violated, the taxonomy was typological, and the phylogenetic analysis was methodologically unsound. Youngest parts of Paleocene time were not sampled during development of the zonation, and the basal two zones involved strata of Cretaceous age. Implications of paleoenvironmental influences on sequences of palynostratigraphic occurrences were not considered. Subjective assertions at many levels remain neither verifiable nor falsifiable, because data from specimens utilized in the published formulation of Paleocene palynozones P1–P6 cannot be reliably tied in their defining area to identifiable stratigraphic sequences at known positions in actual rocks. A rigorous and geologically useful palynological zonation for Paleocene strata in the Rockies is possible, and its development should be pursued. Procedurally, however, any such scheme must (1) be constructed according to sound principles of biostratigraphy; (2) contain accurate information about locations and stratigraphic positions of all samples; and (3) provide publicly accessible and verifiable taxonomic data on compositions of all samples.     

Evidence for a radical mechanism of halogenation of monochlorodimedone catalyzed by chloroperoxidase

A radical species of monochlorodimedone has been characterized by its high reactivity with molecular O2. Horseradish peroxidase greatly accelerated O2 uptake by acidic solutions of this substrate; the enzymatic reaction required exogenous H2O2 only with freshly prepared substrate solutions, and the total substrate oxidized was equal to the sum of H2O2 added and O2 consumed. However, with excess Br- and horseradish peroxidase, or high Br- or Cl- and chloroperoxidase, a 1:1 stoichiometry between H2O2 and substrate was observed. In the absence of halide, the stoichiometry of the chloroperoxidase-catalyzed oxidation of monochlorodimedone changed to two molecules of the organic donor per H2O2. Moreover, in the absence of halide, at substrate:H2O2 ratios greater than 2.0, chloroperoxidase catalyzed significant O2 uptake; this enzyme-dependent autoxidation of monochlorodimedone also occurred in the presence of Cl- or Br-, when H2O2 was limiting. These data, and recent evidence from this laboratory for free hypohalous acid as the first product of chloroperoxidase-catalyzed halide oxidation [B. W. Griffin (1983) Biochem. Biophys. Res. Commun. 116, 873-879], strongly support a mixed enzymatic/nonenzymatic radical chain process as the mechanism for halogenation of monochlorodimedone by chloroperoxidase. Both horseradish peroxidase and chloroperoxidase can catalyze either bromination or oxidation of this substrate, depending on the experimental conditions. Implications of these results for the mechanism of HOCl formation catalyzed by chloroperoxidase are considered.     

A comprehensive metabolite profiling of Isatis tinctoria leaf extracts

A broad-based characterisation of a pharmacologically active dichloromethane extract from Isatis tinctoria leaves was carried out. For a comprehensive picture we also included the polar constituents of I. tinctoria (MeOH extract) and for comparative purposes, the taxonomically closely related plant I. indigotica. Diode array detector, evaporative light scattering detector, atmospheric pressure chemical ionisation and electrospray ionisation mass spectrometry, and electrospray ionisation time-of-flight mass spectrometry detectors were used in parallel to ensure a wide coverage of secondary metabolites with highly diverging analytical properties. Off-line microprobe nuclear magnetic resonance spectroscopy after peak purification by semi-preparative high-pressure liquid chromatography served for structure elucidation of some minor constituents.More than 65 compounds belonging to various structural classes such as alkaloids, flavonoids, fatty acids, porphyrins, lignans, carotenoids, glucosinolates and cyclohexenones were unambiguously identified, and tentative structures were proposed for additional compounds. Numerous compounds were identified for the first time in the genus Isatis, and an indolic alkaloid was discovered.