Makoto Ojika

Ptaquiloside, a novel norsesquiterpene glucoside from bracken, Pteridium aquilinum var. latiusculum

An unstable norsesquiterpene glucoside with a novel illudane skeleton, ptaquiloside (1) has been isolated from bracken fern, Pteridium aquilinum var. latiusculum and the planar structure has been established on the basis of spectral and chemical means.

Firefly luciferase is a bifunctional enzyme: ATP‐dependent monooxygenase and a long chain fatty acyl‐CoA synthetase

Firefly luciferase can catalyze the formation of fatty acyl‐CoA via fatty acyl‐adenylate from fatty acid in the presence of ATP, Mg2+ and coenzyme A (CoA). A long chain fatty acyl‐CoA (C16–C20), produced by luciferase from a North American firefly (Photinus pyralis) and a Japanese firefly (Luciola cruciata), was isolated and identified by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analysis. Of a number of substrates tested, linolenic acid (C18:3) and arachidonic acid (C20:4) appear to be suitable for acyl‐CoA synthesis. This evidence suggests that firefly luciferase within peroxisomes of the cells in the photogenic organ may be a bifunctional enzyme, catalyzing not only the bioluminescence reaction but also the fatty acyl‐CoA synthetic reaction.

Ptaquiloside, a potent carcinogen isolated from bracken fern pteridiumaquilinum var. latiusculum: structure elucidation based on chemical and spectral evidence, and reactions with amino acids, nucleosides, and nucleotides

Abstract The structure of ptaquiloside (1), a potent carcinogenic compound isolated from bracken fern, Pteridium aquilinum var. latiusculum has been elucidated on the basis of chemical and spectral evidence. The dienone 3 generated from 1 under alkaline conditions was shown to be a strong alkylating agent. For the purpose of obtaining the preliminary information on chemical modification of biopolymers such as proteins and DNA with the dienone 3, reactions of 3 with amino acids, nucleosides, and nucleotides have been carried out and the alkylated products have been characterized.

Cystothiazoles C-F, new bithiazole-type antibiotics from the myxobacterium Cystobacter fuscus

Abstract Bithiazole-type antifungal products, cystothiazoles C-F (3–6), have been isolated from a culture broth of the myxobacterium Cystobacter fuscus as minor components. These are structurally related to cystothiazole A (1), which was isolated as a cytotoxic antibiotic from the same microorganism in our previous work. The structures of these compounds were elucidated by spectroscopic analyses. These new compounds inhibit the phytopathogenic fungus, Phytophthora capsici, but are less active than 1.

Specific binding of okadaic acid, a new tumor promoter in mouse skin.

The tumor promoteradaic acid binds specifically to a particulate as well as a cytosolic fraction of various mouse tissues, e.g., skin, brain, lung and colon. The K D value was 21.7 nM for receptors in the particulate fraction and 1.0 nM for those in the cytosolic fraction of mouse skin. The specific binding of [3H]okadaic acid to the particulate fraction of mouse skin was inhibited dose‐dependently byadaic acid, but notaidaic acid tetramethyl ether, an inactive compound, or by other tumor promoters, such as 12‐O‐tetradecanoylphorbol‐13‐acetate and teleocidin. The results suggest a new pathway of tumor promotion mediated through theadaic acid receptor(s).

Production of antibodies and development of a radioimmunoassay for okadaic acid.

An okadaic acid immunogen, prepared by conjugation of okadaic acid to bovine albumin with carbodiimide, was used to immunize two rabbits. The rabbits responded by producing antibodies that neutralized okadaic acids stimulation of arachidonic acid metabolism and this neutralization increased during the course of immunization. The immune sera bound 3H-okadaic acid and this binding also increased with repeated immunization. After absorption of the rabbit IgG with a goat anti-rabbit IgG, binding was reduced greater than 99%. The binding of okadaic acid to the antibodies in one antiserum was inhibited by as little as 0.2 pmoles of unlabelled okadaic acid. The apparent association constant for binding with this antiserum was 4.17 x 10(9) M-1 (35 degrees C). Maitotoxin, teleocidin, 12-O-tetradecanoylphorbol-13-acetate, aplysiatoxin, palytoxin and brevetoxin B when tested at 29, 228, 168, 169, 3.7 and 112 pmole levels, respectively, did not inhibit binding. The serologic and biological activities of okadaic acid after incubation for 60 min in 0.01 N HCl at 35 degrees C or at 100 degrees C at pH 7.2 were unaffected.

Separation of carcinogenic fraction of bracken fern

Isolation of the carcinogen in the boiling water extract of bracken fern was conducted by following the active principle with a carcinogenicity bioassay. Fractionation of the bracken extract was carried out using adsorption on resin (Amberlite XAD-2 and TOYOPEARL HW-40 (c] and organic solvent extraction. A diet containing each of the fractions was given to 7 female Charles River Sprague-Dawley rats (CD rats) of 4 weeks old, except for the second fraction. All 7 rats given the last carcinogenic fraction developed mammary and intestinal tumors and 5 rats had urinary bladder tumors. Ptaquiloside (PT) which induced mammary cancer in female CD rats and rho-hydroxystyrene glycosides were isolated from this fraction.

AMPHIMIC ACIDS AND RELATED LONG-CHAIN FATTY ACIDS AS DNA TOPOISOMERASE I INHIBITORS FROM AN AUSTRALIAN SPONGE, AMPHIMEDON SP. : ISOLATION, STRUCTURE, SYNTHESIS, AND BIOLOGICAL EVALUATION

Abstract Several C 27 –C 30 unsaturated fatty acids have been isolated from an Australian sponge, Amphimedon sp., as human DNA topoisomerase I inhibitors. Three of them, amphimic acids A ( 1 )-C ( 3 ), are unusual fatty acids possessing a cyclopropylidene group, and one is a new C 30 fatty acid 4 . Their structures were elucidated by spectroscopic analysis and chemical degradation. The enantioselective synthesis of 1 was carried out to determine the absolute configuration of amphimic acids. The inhibitory activity of DNA topoisomerase I was evaluated for these natural products and synthetic derivatives.

Isolation, structure, and synthesis of dolastatin D, a cytotoxic cyclic depsipeptide from the sea gare Dolabella auricularia

Abstract Dolastatin D ( 1 ), a cytotoxic cyclic depsipeptide possessing the novel β-amino acid (2 R ,3 R )-3-amino-2-methylbutanoic acid [(2 R ,3 R ]- 3 ] as a component, has been isolated from the Japanese sea hare Dolabella auricularia . The absolute stereostructure of 1 was elucidated on the basis of spectroscopic analysis and chemical degradation and was further confirmed by synthesis.

Coffee and Caffeine Ameliorate Hyperglycemia, Fatty Liver, and Inflammatory Adipocytokine Expression in Spontaneously Diabetic KK-Ay Mice

Epidemiological surveys have demonstrated that habitual coffee consumption reduces the risk of type 2 diabetes. The aim of this work was to study the antidiabetic effect of coffee and caffeine in spontaneously diabetic KK-A(y) mice. KK-A(y) mice were given regular drinking water (controls) or 2-fold diluted coffee for 5 weeks. Coffee ingestion ameliorated the development of hyperglycemia and improved insulin sensitivity. White adipose tissue mRNA levels of inflammatory cytokines (MCP-1, IL-6, and TNFalpha), adipose tissue MCP-1 concentration, and serum IL-6 concentration in the coffee group were lower than the control group. Moreover, coffee ingestion improved the fatty liver. Caffeine ingestion as drinking water also caused an amelioration of hyperglycemia and an improvement of fatty liver. These results suggest that coffee exerts a suppressive effect on hyperglycemia by improving insulin sensitivity, partly due to reducing inflammatory cytokine expression and improving fatty liver. Moreover, caffeine may be one of the effective antidiabetic compounds in coffee.