Germination stimulant from root exudates of Vigna unguiculata

Root exudate of Vigna unguiculata was extracted from a soil system consisting of charcoal and vermiculite. Germination stimulating activity for Striga gesnerioides was found in extracts of the soil system, and an active compound was isolated. The chemical structure of the active ingredient was determined to be (+)-4-O-acetylorobanchol, based on analysis of the spectral data of 1-D and 2-D NMR together with nuclear Overhauser effect (NOE) experiments. Application of the active compound to the seeds of S. gesnerioides at a concentration of 0.35 × 10⁻⁹ mol/disk led to 69% germination. The germination observed with application of GR-24, a positive control, at 0.57 × 10⁻¹⁰ mol/disk was 80%.     

Exogenous quinones inhibit photosynthetic electron transfer in Chloroflexus aurantiacus by specific quenching of the excited bacteriochlorophyll c antenna.

In the photosynthetic green filamentous bacterium Chloroflexus aurantiacus, excitation energy is transferred from a large bacteriochlorophyll (BChl) c antenna via smaller BChl a antennas to the reaction center. The effects of substituted 1,4-naphthoquinones on BChl c and BChl a fluorescence and on flash-induced cytochrome c oxidation were studied in whole cells under aerobic conditions. BChl c fluorescence in a cell suspension with 5.4 microM BChl c was quenched to 50% by addition of 0.6 microM shikonin ((R)-2-(1-hydroxy-4-methyl-3-pentenyl)-5,8-dihydroxy-1, 4-naphthoquinone), 0.9 microM 5-hydroxy-1,4-naphthoquinone, or 4 microM 2-acetyl-3-methyl-1,4-naphthoquinone. Between 25 and 100 times higher quinone concentrations were needed to quench BChl a fluorescence to a similar extent. These quinones also efficiently inhibited flash-induced cytochrome c oxidation when BChl c was excited, but not when BChl a was excited. The quenching of BChl c fluorescence induced by these quinones correlated with the inhibition of flash-induced cytochrome c oxidation. We concluded that the quinones inhibited electron transfer in the reaction center by specifically quenching the excitation energy in the BChl c antenna. Our results provide a model system for studying the redox-dependent antenna quenching in green sulfur bacteria because the antennas in these bacteria inherently exhibit a sensitivity to O(2) similar to the quinone-supplemented cells of Cfx. aurantiacus.     

High-performance Liquid Chromatography of Aflatoxins with Fluorescence Detection

Aflatoxins B_l, B₂, G₁ and G₂ were quantitatively detected by high-performance liquid chromatography on a 12 µl flow-cell in the fluorometric detector using the mobile phase of toluene system instead of chloroform, dichloromethane or methanol system. Various kinds of columns and mobile phases were tested, and fine mutual separation of all the four aflatoxins without quenching their fluorescence was achieved by using sHica gel column and toluene- ethyl acetate-formic acid-methanol (89.0: 7.5: 2.0: 1.5 v/v/v/v). The relationship between the fluorescence peak area and the amount injected was linear in the range of 0.3 ng to 120 ng. This method, as applied to food and feed extracts, is sensitive at the 10~20 ppb levels of the four kinds of aflatoxins.     

Automated high-performance liquid chromatographic method for determination of furosemide in dog plasma

An automated high-performance liquid chromatographic method for the determination of the diuretic drug furosemide has been established. Dog plasma was injected directly into a two-column system with a BSA—ODS (ODS column coated with bovine serum albumin) precolumn and a C₁₈ analytical column for the separation of furosemide. The two columns were automatically switched. Furosemide remained trapped on the precolumn while proteins were eluted to waste. After column switching, furosemide was washed onto the analytical column and analysed without interference. The greatest advantage of the method is its easy performance without manual sample preparation; it requires no extraction or deproteinization. The method allows determination of 0.1–10 μg/ml of furosemide with accuracy and precision comparable with previously reported values. The coefficients of variation obtained from replicate measurements of 1 μg/ml and 5 μg/ml samples were 1.65% and 2.40%, respectively. This method was used to measure the plasma levels of furosemide in beagle dogs to whom the drugs was administered, as a reference, in a toxicological study.     

Occurrence of a New Enzyme Reducing Metmyoglobin in Dolphin Muscle

A new enzyme has been obtained in a crystalline state from the muscle of blue white dolphin. This enzyme resembles to methemoglobin reductase from erythrocyte with respect to (a) elution pattern of DEAE-Sephadex column chromatography, (b) absorption spectra, (c) molecular weight and (d) activity of reducing methemoglobin, metmyoglobin and ferric cytochrome c. However, distinct differences can be observed between two enzymes with regard to (a) sedimentation coefficient, (b) diffusion coefficient, (c) frictional ratio, (d) pH-mobility curve and (e) specific activity of reducing the above three substrates. It is advocated that enzyme is termed metmyoglobin reductase.