Liver injury suppressing compounds from avocado (Persea americana).

To evaluate the protective activity of fruits against liver injury, 22 different fruits were fed to rats with liver damage caused by D-galactosamine, a powerful liver toxin. As measured by changes in the levels of plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST), avocado showed extraordinarily potent liver injury suppressing activity. Five active compounds were isolated and their structures determined. These were all fatty acid derivatives, of which three, namely, (2E,5E,12Z,15Z)-1-hydroxyheneicosa-2,5,12,15-tetraen-4-one, (2E,12Z,15Z)-1-hydroxyheneicosa-2,12,15-trien-4-one, and (5E,12Z)-2-hydroxy-4-oxoheneicosa-5,12-dien-1-yl acetate, were novel.

A lectin from an edible mushroom Pleurotus ostreatus as a food intake-suppressing substance.

In an experiment in which rats were allowed free access to food and water, the rats did not eat the diet containing a mushroom Pleurotus ostreatus even if they were emaciated. A P. ostreatus lectin (POL) was isolated from the mushroom as the food intake-suppression principle. In hemagglutination inhibition assays, Me-alphaGalNAc was the most potent inhibitor among the monosaccharides tested. Among all the sugars tested, 2'-fucosyllactose (Fucalpha1-->2Galbeta1-->4Glc) was the strongest inhibitor and its inhibitory potency was five times greater than that of Me-alphaGalNAc. POL exhibited a binding ability to bovine submaxillary mucin (BSM) and asialo-BSM and the other glycoproteins were inert to the binding. The food intake-suppressing activity of POL was dependent on the dose. The diet containing 0.1% POL caused a 50% decrease in the food intake of rats against the control.

The pir gene of Erwinia chrysanthemi EC16 regulates hyperinduction of pectate lyase virulence genes in response to plant signals.

The plant pathogenic bacterium Erwinia chrysanthemi secretes pectate lyase proteins that are important virulence factors attacking the cell walls of plant hosts. Bacterial production of these enzymes is induced by the substrate polypectate-Na (NaPP) and further stimulated by the presence of plant extracts. The bacterial regulator responsible for induction by plant extracts was identified and purified by using a DNA-binding assay with the promoter region of pelE that encodes a major pectate lyase. A novel bacterial protein, called Pir, was isolated that produced a specific gel shift of the pelE promoter DNA, and the corresponding pir gene was cloned and sequenced. The Pir protein contains 272 amino acids with a molecular mass of 30 kDa and appears to function as a dimer. A homology search indicates that Pir belongs to the IclR family of transcriptional regulators. Pir bound to a 35-bp DNA sequence in the promoter region of pelE. This site overlaps that of a previously described negative regulator, KdgR. Gel shift experiments showed that the binding of either Pir or KdgR interfered with binding of the other protein.

Dietary eritadenine modifies plasma phosphatidylcholine molecular species profile in rats fed different types of fat.

The effect of dietary eritadenine on plasma phosphatidylcholine (PC) molecular species composition was investigated in relation to its hypocholesterolemic action in rats fed different types of fats (olive oil, corn oil and linseed oil; 100 g/kg diet). Eritadenine supplementation (50 mg/kg diet) significantly decreased the plasma total cholesterol concentration, irrespective of dietary fat sources, and without change in the order of plasma cholesterol concentration among the fat groups (corn oil > olive oil > linseed oil). Eritadenine significantly decreased the ratio of phosphatidylcholine (PC) to phosphatidylethanolamine (PE) in liver microsomes of all the fat groups, while the PC:PE ratio was unaffected by dietary fat type. The fatty acid and molecular species composition of plasma PC was affected either directly or indirectly by the fatty acid composition of dietary fats. The proportion of linoleic acid and linoleic acid-containing molecular species (16:0-18:2 and 18:0-18:2) in plasma PC was the highest in rats fed linseed oil, despite the fact that linoleic acid concentration of linseed oil was only 1/3 that of corn oil. Eritadenine supplementation significantly increased the proportion of linoleic acid and linoleic acid-containing molecular species, especially 16:0-18:2, in plasma PC, irrespective of dietary fat source. Altered plasma PC molecular species composition, as represented by an increase in 16:0-18:2 PC, might contribute to the hypocholesterolemic action of eritadenine.

Effect of capsianoside, a diterpene glycoside, on tight-junctional permeability.

Previous work (Hashimoto et al., (1994) Biosci. Biotech. Biochem. 58, 1345) revealed that a sweet pepper extract enhanced the tight-junctional (TJ) permeability of a human intestinal Caco-2 cell monolayer. In the present study, the substance which modulated the TJ permeability was chromatographically purified from the extract. The active substances were identified as capsianosides A-F, diterpene glycosides. Treatment of the cells with capsianoside F, the most active compound, decreased the cellular G-actin content by 40% and increased the F-actin content by 16%. The effect of capsianoside F was significantly suppressed by disturbing the cytoskeletal structure with cytochalasin D at a low dose (50 ng/ml). These results suggest that capsianosides affected the cytoskeletal function by modulating the reorganization of actin filaments, by which the TJ structure and permeability were changed. The possible involvement of a PKC inhibition in the mechanism of an increase in TJ permeability is also suggested.

A lectin from mycelia of the fungus Ganoderma lucidum.

A lectin (GLL-M) was isolated from mycelia of Ganoderma lucidum using affinity chromatography on BSM-Toyopearl. GLL-M is a monomer in its native form with a M(r) of 18,000. Another lectin was also purified from fruiting bodies of the same fungus. The two lectins were partially compared with each other.

A pyradine-derivative from the mushroom Albatrellus confluens.

A novel pyradine-derivative was isolated from the mushroom Albatrellus confluens. This compound promoted melanin synthesis by B16 melanoma cells.

A sialic acid-binding lectin from the mushroom Hericium erinaceum.

A lectin was isolated from the mushroom Hericium erinaceum. This lectin is composed of two different subunits of 15 and 16 kDa and the molecular mass of the intact lectin was estimated to be 54 kDa by gel filtration. It exhibits specificity towards sialic acids, especially N-glycolylneuraminic acid.

Isolation of plasma cholesterol-lowering components from ningyotake (Polyporus confluens) mushroom.

The present study was undertaken to isolate component(s) which contributes to the hypocholesterolemic action of Ningyotake (Polyporus confluens) mushroom. The mushroom powder was extracted with 80% ethanol, and the extract and residue were fractionated into five fractions according to the solubility to solvents. When each fraction was added to a diet containing 1% cholesterol and 0.25% sodium cholate and fed to rats, the plasma cholesterol level was significantly decreased only by ethyl acetate-soluble fraction. Therefore, ethyl acetate-soluble fraction was further fractionated by silica gel column chromatography. Two major compounds, which comprised 45.0% and 28.5% of the ethyl acetate-soluble fraction, were obtained in a pure form by the chromatography, and the compounds were identified as grifolin (2-trans, trans-farnesyl-5-methylresorcinol) and neogrifolin (4-trans, trans-farnesyl-5-methylresorcinol), respectively. The addition of grifolin and neogrifolin to the high cholesterol diet was found to lower plasma cholesterol level significantly.