Some cyst-forming nematodes, such as potato cyst nematode (Globodera rostochiensis) and soybean cyst nematode (Heterodera glycines), are known as serious pests in agriculture. The eggs in these cysts remain dormant until hatching is stimulated by root exudates from host plants. Since the first discovery by Baunacke (1922) of this phenomenon for the potato cyst nematode, the isolation of the stimulus has been the object of considerable research. However, its extremely low concentration and relative instability have prevented its isolation. In this article, we describe how we have isolated the first hatching stimulus, glycinoeclepin A, from the dried roots of kidney bean (Phaseolus vulgaris), one of the host plants of the nematode. This substance is active at the concentration of 10-11-12g/ml in vitro against the soybean cyst nematode.
Simple anthocyanins are unstable in dilute aqueous solutions around pH 4-7, but some highly acylated anthocyanins were found to be stable in such solutions Structures of several highly acylated anthocyanins have been elucidated mainly by means of 1H-NMR including the NOE relief method. Stability of the anthocyanins has been assumed to come from intramolecular sandwich-type stacking of anthocyanidin nucleus and two aromatic acyl moieties.
The presence of a molt-inhibiting hormone (MIH) in crustaceans versus the molting hormone (ecdysteroids) has been biologically demonstrated, however, only a little of the chemical nature of MIH is known so far Our attempt to isolate MIH produced in the X-organ of the eyestalks (ES) resulted in the characterization of xanthurenic acid as an ecdysone biosynthesis inhibitor (EBI) In addition, it was found that 3-hydroxy-L-kynurenine (3-OH-K) present in the X-organ of ES was also biotransformed into xanthurenic acid. The inhibitory action was shown in the cultured Y-organ-complex homogenate as well as in the crayfish by injection of 3-OH-K that revealed the delay of ecdysis. The preliminary study of ED50 of the active compounds appeared to account for most of but not the full potency of ES extract. Therefore, a molt-inhibiting phenomena is probably the result of the action by the multiple factors including EBI. After the mode of inhibitory action of the recently isolated sinusgland neuropeptide is shown, the involvement of a hormone in the negative control of molting will be clarified.
Since the discovery of 1, 25-dihydroxyvitamin D3, our knowledge of the metabolic activation and the mode of action of vitamin D has expanded dramatically during the past 15 years. About 40 kinds of the metabolites were isolated. Many analogs of those metabolites have been synthesized in order to obtain higher activity and to separate various biological activities. Recently, a specific receptor for 1, 25- (OH) 2D3 was demonstrated in many tissues and tumor cells, and the induction of cell differentiation of myeloid leukemia cells by 1, 25- (OH) 2D3 was reported. Vitamin D analogs have been tested for the activity. Usually parallel activities were observed for the calcium regulation effect and cell differentiation. Synthetic analogs, 24-homo-1, 25- (OH) 2D3, 26, 27-diethyl-1, 25- (OH) 2D3, and 24, 24-F2-24-homo-1, 25- (OH) 2D3 were found to be 10 fold more potent than 1, 25- (OH) 2D3 in inducing differentiation of HL-60 cells, but almost inactive in calcium regulation. Thus, the separation of two major actions of 1, 25- (OH) 2D3 could be achieved.
Biosynthetic means using 13C labeled precursors were applied to the structure elucidation of new polyketide antibiotics which have been discovered in our laboratory. It was demonstrated that intra- and intermolecular 13C-13C couplings in 13C NMR spectrum of antibiotics highly enriched with 13C precursors afforded useful informations for structure elucidation. Microbial transformation of macrolide antibiotics under the presence of a polyketide biosynthetic inhibitor, cerulenin, led to the production of new “hybrid” macrolides. Further, production of the new hybrid antibiotic mederrhodins by a genetically engineered strain of Streptomyces is described.
It has been known since 1892 that a cell wall outermost layer of Gram-negative bacteria possesses an endotoxin which exhibits very multiple biological activities related to a self-defence mechanism of human being. Endotoxin activity is located in lipid A part in lipopolysaccharide (LPS) of cell wall. We could propose a chemical structure of E.coli lipid A and achieved a total synthesis of it, resulting in a first clarification of the chemical entity of endotoxin. Furthermore, syntheses of Salmonella and Chromobacterium type lipid As as well as several biosynthetic precursors were also performed. Structure-activity relationship was discussed from biological activities of the synthetic lipid A analogs.
Recent aspects of synthetic studies on oligosaccharides of N-glycoproteins are described in three parts ; (1) synthesis of core structure, (2) synthesis of variable region, (3) coupling between core structure and variable region. Synthesis of core structure, the trisaccharides containing one β-D-mannopyranosyl residue and two 2-acetamide-2-deoxy-β-D-glucopyranosyl residues, was designed by employing a protected chitobiosyl derivative and a di-O-allyl-di-O-benzyl-mannopyranosyl donor The β-mannopyranosylations were achieved by use of Paulsen's promotor. Synthesis strategies for variable region of both high-mannose type and complex type were developed mainly by taking advantage of new regioselective protective procedures. Coupling between the core structure and variable regions were successfully achieved by use of oligosaccharide halides as well as trichloroacetoimidates as the glycosyl donors.