Fungistatic activity of iron-free bovin lactoferrin against several fungal plant pathogens and antagonists

Lactoferrin (LF) is a member of the transferrin family of iron-binding glycoproteins. It is also a multifunctional protein of 80 kDa that is synthesized by glandular epithelial cells and secreted into mucosal fluid. High levels of LF are present in colostrom and milk and low levels in tears, saliva, and gastrointestinal and reproductive secretions. Data regarding the antifungal effects of LF are limited. Studies have been performed on Candida albicans, which demonstrated that LF inhibits the growth of this fungus. This study reports the results of experiments carried out in order to evaluate the effects of LF on the growth of 11 fungi, which were isolated from plants and soils. These experiments employed the methods of amended agar utilizing nine different concentration levels of LF (0, 0.001, 0.01, 0.1, 1, 10, 100, 1000, 5000 mg L(-1)). The effects of LF on the growth of these fungi were based on measures of the radial growth of the fungal colonies expressed both as percentage of inhibition and as IC(50) values (the concentration at which the fungal growth was inhibited by 50% relative to controls). LF had no effects on Alternaria alternata, Gliocladium roseum, Fusarium solani and Colletotrichum lindemuthianum. It did, however, inhibit the growth of Aspergillus niger, Trichoderma viride, Sclerotinia sclerotiorum, Sclerotium rolfsii, Rhizoctonia solani and Phoma exigua to the point that their IC(50) values ranged from 31.1 mg L(-1) for S. sclerotiorum to 952 mg L(-1) for T. viride.     

A new in vitro approach for the simultaneous determination of phase I and phase II enzymatic activities of human hepatocyte preparations

Primary hepatocytes are still the best qualified in vitro system to anticipate drug metabolism in man. Recent advances in hepatocytes cryopreservation have notably increased their use not only for drug metabolism studies, but also for other applications such as cell transplantation. Evaluation of the drug-metabolizing competence of each hepatocytes preparation is needed. To date, the metabolic characterization of hepatocytes preparations relies on the assessment of phase I activities and the role of phase II enzymes receives little attention. A novel approach for the rapid assessment of the metabolic functionality of hepatocytes has been developed. A five-probe cocktail was used to simultaneously determine the enzymatic activities of major human phase I CYPs (CYP1A2, CYP2A6, CYP2C9, CYP2E1, CYP3A4), as well as two phase II enzymes: glucuronidase (UGTs) and sulfotransferase (SULT). Liquid chromatography/tandem mass spectrometry was used as the technique of choice for the determination of the enzymatic activities in a single run. Results showed that the method described herein permits a rapid assessment of the metabolic capabilities of human hepatocyte preparations as well as an estimation of the quality of freshly isolated or cryopreserved hepatocytes.     

Temperature Dual Enantioselective Control in a Rhodium‐Catalyzed Michael‐Type Friedel–Crafts Reaction: A Mechanistic Explanation

By changing the temperature from 283 to 233 K, the S (99 % ee) or R (96 % ee) enantiomer of the Friedel–Crafts (FC) adduct of the reaction between N‐methyl‐2‐methylindole and trans‐β‐nitrostyrene can be obtained by using (S_Rh,R_C)‐[(η⁵‐C₅Me₅)Rh{(R)‐Prophos}(H₂O)][SbF₆]₂ as the catalyst precursor. This catalytic system presents two other uncommon features: 1) The ee changes with reaction time showing trends that depend on the reaction temperature and 2) an increase in the catalyst loading results in a decrease in the ee of the S enantiomer. Detection and characterization of the intermediate metal–nitroalkene and metal–aci‐nitro complexes, the free aci‐nitro compound, and the FC adduct‐complex, together with solution NMR measurements, theoretical calculations, and kinetic studies have allowed us to propose two plausible alternative catalytic cycles. On the basis of these cycles, all the above‐mentioned observations can be rationalized. In particular, the reversibility of one of the cycles together with the kinetic resolution of the intermediate aci‐nitro complexes account for the high ee values achieved in both antipodes. On the other hand, the results of kinetic measurements explain the unusual effect of the increment in catalyst loading.     

Asymmetric 1,3-dipolar cycloaddition reaction of α,β-unsaturated nitriles with nitrones catalyzed by chiral-at-metal rhodium or iridium complexes

The aqua complexes (S_M,R_C)-[(η⁵-C₅Me₅)M{(R)-Prophos}(H₂O)](SbF₆)₂ (M = Rh, Ir; (R)-Prophos = 1,2-bisdiphenylphosphino propane) catalyze the 1,3-dipolar cycloaddition reaction (DCR) of nitrones with α,β-unsaturated nitriles with low-to-moderate enantioselectivity. The involved catalysts [(η⁵-C₅Me₅)M{(R)-Prophos}(α,β-unsaturated nitrile)](SbF₆)₂, isolated as mixtures of the (S_M,R_C)- and (R_M,R_C)-diastereomers, have been fully characterized, and the molecular structure of the complexes (S_Rh,R_C)-[(η⁵-C₅Me₅)Rh{(R)-Prophos}(cis-2-pentenenitrile)](SbF₆)₂ and (S_Ir,R_C)-[(η⁵-C₅Me₅)Ir{(R)-Prophos}(acrylonitrile)](SbF₆)₂ has been determined by X-ray diffraction. The (R)-at-metal epimers isomerize to the (S)-at-metal counterparts. Diastereopure (S_M,R_C)-[(η⁵-C₅Me₅)M{(R)-Prophos}(α,β-unsaturated nitrile)](SbF₆)₂ complexes catalyze the above-mentioned DCR in a stoichiometric manner with up to 97% ee. The results make clear the influence of the metal configuration on the catalytic stereochemical outcome. The catalysts can be recycled without significant loss of either activity or selectivity.     

Transmission of trans effects in dinuclear complexes.

The substitution of a terminal hydride ligand in the complexes [Ir(2)(mu-H)(mu-Pz)(2)H(3)(L)P(i)Pr(3))(2)] (L = NCCH(3) (1) or pyrazole (3)) by chloride provokes a significant change in the lability of the L ligand, despite the fact that the substituted hydride and the L ligand lie in opposite extremes of the diiridium(III) complexes. Detailed structural studies of complex 3 and its chloro-trihydride analogue [Ir(2)(mu-H)(mu-Pz)(2)H(2)Cl(HPz)(P(i)Pr(3))(2)] (4) have shown that this behavior is a consequence of the transmission of ligand trans effects from one extreme of the molecule to the other, with the participation of the bridging hydride. Extended Hückel calculations on model diiridium complexes have suggested that such trans effect transmissions are due to the formation of molecular orbitals of sigma symmetry extended along the backbones of the complexes. This is also an expected feature for metal-metal bonded complexes. The feasibility of the transmission of ligand trans effects and trans influences through metal-metal bonds and its relevance to the understanding of both the reactivity and structures of metal-metal bonded dinuclear compounds have been substantiated through structural studies and selected reactions of the diiridium(II) complexes [Ir(2)(mu-1,8-(NH)(2)naphth)I(CH(3))(CO)(2)(P(i)Pr(3))(2)] (isomers 6 and 7) and their cationic derivatives [Ir(2)(mu-1,8-(NH)(2)naphth)(CH(3))(CO)(2)(P(i)Pr(3))(2)](CF(3)SO(3)) (isomers 8 and 9).