Kenneth J. Friesen

Aqueous solubilities of selected 2,3,7,8-substituted polychlorinated dibenzofurans (PCDFs)

Abstract Aqueous solubilities are reported for a series of 2,3,7,8-chlorinated dibenzofurans, 2,3,7,8-tetra-, 2,3,4,7,8-penta-, 1,2,3,6,7,8-hexa-, 1,2,3,4,7,8-hexa-, and 1,2,3,4,6,7,8-heptachlorodibenzofuran, at 22.7°C. The solubilities of the solid solutes decrease approximately 8-fold for each additional chlorine in the structure, ranging from 419 ± 15 ng/L for 2,3,7,8-T4CDF to 1.35 ± 0.17 ng/L for 1,2,3,4,6,7,8-H7CDF.

Quantum yields of the direct Phototransformation of 1,2,4,7,8‐penta‐ and 1,2,3,4,7,8‐hexachlorodibenzofuran in aqueous Acetonitrile and their sunlight half‐lives∗

Photochemistry of two polychlorodibenzofurans (PCDFs), 1,2,4,7,8‐pentachlorodibenzofuran (1,2,4,7,8‐P5CDF) (1) (3.870 × 10‐6M) and 1,2,3,4,7,8‐H6CDF (2) (1.272 × 10‐6M) dissolved in water‐acetonitrile (1:1 v/v) was investigated using wavelengths near 313nm. The quantum yields for the direct phototransformation of P5CDF 1 and H6CDF 2 were found to be (1.295±0.087) x 10‐2 and (6.964±0.234) × 10‐4, respectively. The quantum yields and absorption spectral data for PCDFs 1 and 2 together with solar intensity data from the literature were used to determine the direct sunlight (environmental) photolytic transformation first‐order rate constants of these pollutants present in aquatic systems under conditions of varying sunlight during spring, summer, fall, and winter season. For instance, in summer, the calculated midday, midseason sunlight photolysis first‐order rate constants for furans 1 and 2 near the surface of water bodies at 40° north latitude were 3.082 ±0.207 and (11.630 ± 0.391)× 10‐2h‐1, respectively; ...

Antimicrobial Compounds from Drypetes staudtii

Antimicrobial‐directed phytochemical investigation of the MeOH extract of Drypetes staudtii afforded two new compounds, 4,5‐(methylenedioxy)‐o‐coumaroylputrescine (1), 4,5‐(methylenedioxy)‐o‐coumaroyl‐4′‐N‐methylputrescine (2), along with seven known natural products 4α‐hydroxyeremophila‐1,9‐diene‐3,8‐dione (3), drypemolundein B (4), friedelan‐3β‐ol (5), erythrodiol (6), ursolic acid (7), p‐coumaric acid (8), and β‐sitosterol (9). Structures of compounds 1 – 9 were elucidated with the aid of extensive NMR and mass spectral studies. All of the isolates exhibited antibacterial activity against Gram‐positive and Gram‐negative bacteria with minimum inhibitory concentration (MIC) in the range of 8 – 128 μg/ml. Compounds 1 – 2 were also moderately active against Candida albicans with an MIC value of 32 μg/ml.