Allelopathy in the natural and agricultural ecosystems and isolation of potent allelochemicals from Velvet bean (Mucuna pruriens) and Hairy vetch (Vicia villosa).

We have studied on allelopathy of plants and developed methods to identify the effective substances in root exudates, leaf leacheate, and volatile chemicals emitted from plants. We found traditional cover plants that show allelopathic activity are useful for weed control. It could eliminate the use of synthetic chemicals for this purpose. Allelopathy is a natural power of plants to protect themselves by producing natural organic chemicals. Some endemic plants in Asia, already known by farmers in the region, as either cover crops used in intercropping, hedgerow, or agroforestry, were found to possess strong allelopathic abilities. Our group identified several allelochemicals from these plants. These allelopathic cover crops, mostly leguminous plants, provide protein rich food, and grow easily without artificial fertilizers, herbicides, insecticides and fungicides. In this regards, these allelopathic cover crops could save food shortage in rural area, and are useful for environmental conservation. Screenings of allelopathic plants by specific bioassays and field tests have been conducted. Hairy vetch (Vicia villosa) and Velvet bean (Mucuna pruriens) are two promising species for the practical application of allelopathy. An amino acid, L-DOPA, unusual in plants, plays an important role as allelochemical in Velvet bean (Mucuna pruriens). Hairy vetch is the most promising cover plant for the weed control in orchard, vegetable and rice production and even for landscape amendment in abandoned field in Japan. We have isolated "cyanamide", a well known nitrogen fertilizer, from Hairy vetch. This is the first finding of naturally produced cyanamide in the world.     

Balance of Activities of Alcohol Acetyltransferase and Esterase in Saccharomyces cerevisiae Is Important for Production of Isoamyl Acetate

Isoamyl acetate is synthesized from isoamyl alcohol and acetyl coenzyme A by alcohol acetyltransferase (AATFase) in Saccharomyces cerevisiae and is hydrolyzed by esterases at the same time. We hypothesized that the balance of both enzyme activities was important for optimum production of isoamyl acetate in sake brewing. To test this hypothesis, we constructed yeast strains with different numbers of copies of the AATFase gene (ATF1) and the isoamyl acetate-hydrolyzing esterase gene (IAH1) and used these strains in small-scale sake brewing. Fermentation profiles as well as components of the resulting sake were largely alike; however, the amount of isoamyl acetate in the sake increased with an increasing ratio of AATFase/Iah1p esterase activity. Therefore, we conclude that the balance of these two enzyme activities is important for isoamyl acetate accumulation in sake mash.     

Second sphere coordination behavior of aquo and amine ligands bound to a η-benzeneruthenium(II) cation

The bis(oxazoline) ligand, 2,2-bis[4(R)-phenyl-1,3-oxazolon-2-yl]propane (bpop), was introduced to the η⁶-benzenemthenium(II) moiety on treatment with [Ru(η⁶-C₆H₆)Cl₂]₂ to give [Ru(η⁶-C₆H₆)(bpop)Cl]⁺. Aquo and amine complexes [Ru(η⁶-C₆H₆)(bpop)(L)]²⁺ (L = H₂O (1), NH₂R; R = H (2) , Me (3) , and n-Bu (4) ) were prepared by treating the chloride complex with AgBF₄ in the presence of L. X-ray structure determinations of 1 and 3 were carried out. Both complexes possessed a three-leg piano stool structure with the N or O donors located at the three comers of a pseudo octahedron. The aquo complex 1 exhibited a dynamic NMR feature in which two magnetically nonequivalent oxazoline parts observed at lower temperatures were interchanged with each other at higher temperatures. This observation was ascribed to the formation of a C₂-symmetric 16-electron intermediate via Ru-OH₂ cleavage, which is slower in acetone than in dichloromethane owing to more effective solvation by acetone around hydrogens of the coordinated water molecule. The two diastereotopic N-hydrogens of 4 underwent deuterium exchange with CD₃OD with greatly different rates from each other owing to different energy of NHO (D) (CD₃) interaction. Carboxylate and sulfonate ions (A⁻) formed second sphere complexes with 4 by means of NHA⁻ hydrogen bonding, as evidenced by continuous shift of NH₂ resonances with increasing amounts of the anions added.     

New PEG2 type polyethylene glycol derivatives for protein modification

Although proteins with 2,4-bis (o-methoxypolyethylene glycol)-6-chloro-s-triazine (PEG2-Cl) as a divalent PEG modification have some advantages compared to proteins with the linear PEG modification, PEG2Cl cannot react with amino groups at neutral pH. Therefore, we have prepared new PEG2 derivatives that have an activated ester as the functional group. We confirmed that these derivatives are useful for the divalent modification of proteins, such as bSOD and rhG-CSF. © Rapid Science Ltd. 1998     

Isolation and identification of potent allelopathic substances in rattail fescue

Aqueous methanol extracts of rattail fescue (Vulpia myuros) inhibited the growth of roots and shoots of cress (Lepidium sativum), lettuce (Lactuca sativa), alfalfa (Medicago sativa), timothy (Phleum pratense), Digitaria sanguinalis and Lolium multiflorum. Increasing the extract concentration increased the inhibition, suggesting that rattail fescue may have growth inhibitory substances and possess allelopathic potential. The aqueous methanol extract of rattail fescue was purified and two main inhibitory substances were isolated and identified by spectral data as (−)-3-hydroxy-β-ionone and (+)-3-oxo-α-ionol. Both substances inhibited root and shoot growth of cress at concentrations greater than 0.3 μM. The concentrations required for 50% growth inhibition on root and shoot growth of cress, lettuce, alfalfa, timothy, D. sanguinalis and L. multiflorum were 2.7–19.7 μM for (−)-3-hydroxy-β-ionone, and 2.1–34.5 μM for (+)-3-oxo-α-ionol. The concentration of (−)-3-hydroxy-β-ionone and (+)-3-oxo-α-ionol, respectively, in rattail fescue was 7.8 and 3.7 μg g⁻¹ fresh weight. Considering the endogenous level and the inhibitory activity, (−)-3-hydroxy-β-ionone and (+)-3-oxo-α-ionol may work as allelopathic substances in rattail fescue through the growth inhibition of neighboring plant species.     

Efficient extraction of thioreodoxin from Saccharomyces cerevisiae by ethanol

Thioredoxin, an antioxidant protein, is a promising molecule for development of functional foods because it protects the gastric mucosa and reduces the allergenicity of allergens. To establish a method for obtaining an ample amount of yeast thioredoxin, we found here that thioredoxin is released from Saccharomyces cerevisiae by treatment with 20% ethanol. We also found that Japanese sake contains a considerable amount of thioredoxin.     

Collagen vitrigel membrane useful for paracrine assays in vitro and drug delivery systems in vivo

We previously succeeded in converting a soft and turbid disk of type-I collagen gel into a strong and transparent vitrigel membrane utilizing a concept for the vitrification of heat-denatured proteins and have demonstrated its protein-permeability and advantage as a scaffold for reconstructing crosstalk models between two different cell types. In this study, we observed the nano-structure of the type-I collagen vitrigel membrane and verified its utility for paracrine assays in vitro and drug delivery systems in vivo. Scanning electron microscopic observation revealed that the vitrigel membrane was a dense network architecture of typical type-I collagen fibrils. In the crosstalk model between PC-12 pheochromocytoma cells and L929 fibroblasts, nerve growth factor (NGF) secreted from L929 cells passed through the collagen vitrigel membrane and induced the neurite outgrowth of PC-12 cells by its paracrine effect. Also, the collagen vitrigel membrane containing vascular endothelial growth factor (VEGF) showed sustained-release of VEGF in vitro and its subcutaneous transplantation into a rat resulted in remarkable angiogenesis. These data suggest that the collagen vitrigel membrane is useful for paracrine assays in vitro and drug delivery systems in vivo.     

Improvement of tolerance to freeze-thaw stress of baker's yeast by cultivation with soy peptides

The tolerance to freeze–thaw stress of yeast cells is critical for frozen-dough technology in the baking industry. In this study, we examined the effects of soy peptides on the freeze–thaw stress tolerance of yeast cells. We found that the cells cultured with soy peptides acquired improved tolerance to freeze–thaw stress and retained high leavening ability in dough after frozen storage for 7 days. The final quality of bread regarding its volume and texture was also improved by using yeast cells cultured with soy peptides. These findings promote the utilization of soy peptides as ingredients of culture media to improve the quality of baker’s yeast.