Comparison of the Phytotoxic Effects of Usnic Acid on Cultures of Free-Living Alga <Emphasis Type="Italic">Scenedesmus quadricauda</Emphasis> and Aposymbiotically Grown Lichen Photobiont <Emphasis Type="Italic">Trebouxia erici</Emphasis>

The phytotoxic effects of the lichen secondary metabolite—usnic acid on cultures of free living alga—Scenedesmus quadricauda (UTEX 76) and aposymbiotically grown lichen photobiont Trebouxia erici (UTEX 911) were assessed. We found a relatively strong inhibition effect of usnic acid on the growth of alga Scenedesmus, accompanied by an increase of cell size, an alteration of assimilation pigment composition, followed by strong degradation of chlorophyll a, a decrease of chlorophyll a fluorescence, and an increase of reactive oxygen species in the cells. The content of soluble proteins remained a stable parameter. Phytotoxicity of usnic acid on cultures of Trebouxia photobiont was significantly lower. Usnic acid in lichens may act as an allochemical that controls the division of photobiont cells, thereby regulating the balance between the photobiont and mycobiont forming thallus. Higher tolerance to usnic acid in Trebouxia cultures may be an adaptation resulting from the long term co-evolution of these algae with fungi that produce secondary metabolites.     

Biocatalysis of linoleic acid to conjugated linoleic acid

CLA refers to a group of geometrical and positional isomers of linoleic acid (LA) with conjugated double bonds. CLA has been reported to have diverse health benefits and biological properties. Traditional organic synthesis is highly capital-intensive and results in an isomeric mixture of CLA isomers. Biotechnology presents new alternatives to traditional lipid manufacturing methods. The objective of this study was to examine the effect of protein isolation procedures on linoleate isomerase (LAI) recovery from microbial cells and biocatalysis of LA to CLA. Protein isolation experiments were carried out using Lactobacillus acidophilus L1 and two strains of Lactobacillus reuteri (ATCC 23272 and ATCC 55739). Under the same assay conditions, ATCC 55739 had the highest LAI activity among the microbial cultures examined in this study. Efficiency of cell lysis methods, which included various combinations of lysozyme and mutanolysin treatments in combination with sonication and osmotic rupture of cells with liquid nitrogen, was very low. Although treatment of cell material with a detergent (octylthioglucoyranoside) freed a significant amount of LAI activity into the solution, it was not sufficient to recover all the LAI activity from the residual cells. Crude LAI preparations produced mainly the cis-9,trans-11 CLA isomer. Time and substrate/protein ratio had a significant effect on biocatalysis of LA to CLA. It appears that the mechanism and kinetics of enzymatic conversion of LA to CLA are quite complex and requires further research using pure LAI preparations. Published with approval of the Director, Oklahoma Agricultural Experiment Station.     

Umsetzung von 1-(2-Benzoxazolon-3-yl)-2-propanonen mit Hydrazinhydrat

Reaction of 1-(2-Benzoxazolon-3-yl)-2-propanones with Hydrazinhydrate . The reaction of 1-(2-benzoxazolon-3-yl)-2-propanones 1a–g with hydrazinhydrate is studied. It is shown that according to the reactional conditions are obtained hydrazones 2a–b , azines 4a–b and 6-Methyl-4-(2-hydroxyphenyl)-2,3,4,5-tetrahydro-1,2,4-triazine-3-ones 6a–g . The structure of the products is discussed on the base of i.r. and n.m.r.-spectras.