Takashi Tokuyama

Steroidal alkaloids (batrachotoxins and 4β-hydroxybatrachotoxins), “indole alkaloids” (calycanthine and chimonanthine) and a piperidinyldipyridin

Abstract Skin extracts from the Colombian poison-dan frog Phytlobates terribilis contain three major steroidal alkaloids; Batrachotoxin, homobatrachotoxin and batrachotoxinin A. Minor congeners of batrachotoxin and homobalrachotoxin containing a 4β-OH substituent are identified based on mass spectra and proton and carbon-13 NMR. Two “indole alkaloids” 1-calycanthine and d-chimonanthine, enantiomeric to the same compounds from plants, and noranabasamine (5-(2-piperidyl)2,3-dipyridine), a des-N-Me analog of the plant alkaloid anabasamine, are present as minor constituents.

New classes of amidine, indolizidine and quinolizidine alkaloids from a poison-frog, Dendrobates pumilio (Dendrobatidae)

Abstract Skin extracts from the Panamanian poison-frog Dendrobates pumilio afforded three major alkaloids of known structure, namely the 6-ylidene-8-hydroxy-8-methylindolizidines pumiliotoxin A and B and the cis -decahydroquinoline pumiliotoxin C. Other alkaloids include congeners 307F and 321 of pumiliotoxin A, allopumiliotoxins 267A, 323B and 339A, a 7-alkylidene-9-hydroxy-9-methylquinolizidine 223G, homologous to the pumiliotoxin-A class of dendrobatid alkaloids, a 5-alkynyl-8-methylindolizidine 205A, a 5-alkenyl-8-methyl-indolizidine 235B, a 3,6,8-trimethyl-12-azatricyclo[7.2.1.05,12]-2-(dodecene 205B, a 6-hydroxy analog (211A) of the cis-decahydroquinoline pumiliotoxin C, and three tricyclic amidines 222, 236, 252. The allopumiliotoxins 323B and 339A are 7-axial-hydroxy congeners of pumiliotoxin A and B, respectively, and allopumiliotoxin 267A is the 7-axial-hydroxy analog of pumiliotoxin 251D. Structures are proposed for 307F, 321, 223G, 205A, 235B, 205B, 211A, 222, 236 and 252, based primarily on mass and nuclear magnetic resonance spectral analysis.

Alkaloids from dendrobatid poison frogs: trans-decahydroquinolines and indolizidines

Abstract Skin extracts from one population of the Colombian poison-frog Dendrobates histrionicus contain a variety of histrionicotoxins (2,7-disubstituted 1-azaspiro(5.5)-undecan-8-ols) and other alkaloids. Two of tha major alkaloids are trans-dacahydro-quinolines whose gross structures based on mass and nuclear magnetic resonance spectral analysis are 2,5-diallyl- trans -dacahydroquinoline 219A and 2-allyl-5-pent-2-en-4-ynyl- trans -dacahydroquinoline 243A. A minor isomer, 243A°, is also present. X-ray crystalloraphic analysis of 219A-HC1 raveals the absolute configuration as [2S,4aS,5S,8aS]2,5-diallyl- trans -decahydroauinoline. A dihydroxydihydro-219A was also isolated and shown by nuclear magnetic resonance spectral analyais to be 2-allyl-5-(2,3-dihydroxypropyl)- trans -decahydroquinoline (253D). Four of the alkaloids from Dendrobates histrionicus are indolizidines namely (5E,9E)-3-n-butyl-5-n-propylndolizidine 223AE, its two ω-hydroxy congeners 239AE (hydroxypropyl) and 239CD (hydroxybutyl), and (5E,9E)-3-n-butyl-5-mathylindolizidine 195E. Structures are based on nuclear magnetic resonance spectral analysis.

Isolation of an activator for prostaglandin hydroperoxidase from bovine vesicular gland cytosol and its identification as uric acid

Abstract The enzymatic conversion of prostaglandin G 1 to H 1 was stimulated by an activator present in the cytosol of bovine vesicular gland. The activator was purified by Sephadex G-25 gel filtration and Dowex 1 column chromatography. The purified activator was identified to be uric acid by thin layer chromatography, ultraviolet and infrared absorption spectroscopy and combined gas chromatography-mass spectroscopy. Among various purine compounds tested, only uric acid and 2,8-dihydroxyadenine were active.

Alkaloids from dendrobatid poison frogs: Further cis-decahydroquinolines and 8-methylindolizidines

Abstract Skin extracts from one population of the poison frog Dendrobates auratus contain a variety of alkaloids, including 2,5-disubstituted-cis-decahydroquinolines and 5-substituted-8-methylindolizidines. Three of the major alkaloids are cis-decahydroquinolines, whose structures based on NNR spectral analyses are 2,5-diallyl-cis-decahydroquinoline (cis- 219A ), 2-allyl-5(pent-2-en-4-ynyl)-cis-decabydroquinoline (cis- 243A ) and 5-methyl-2-propyl-cis-decahydroquinoline (cis- 195A ; the last is identical with “pumiliotoxin C” previously isolated from the poison frog Dendrobates pumilio . Alkaloids cis- 219A and cis- 243A differ fron cis- 195A in configuration at the C-2 position. Another poison frog, Dendrobates histrionicus , was previously shown to produce nearly exclusively trans-decahydroquinoline isomers of 219A and 243A . NMR analyses indicate that the structure of a minor alkaloid from Dendrobates auratus is 5-(pent-2-en-4-ynyl)-8-methylindolizidine ( 203A ). Two additional 8-methylindolizidines isolated from Dendrobates pumilio are 5-(hept-4,6-dienyl)-8-methylindolizidine ( 233D ) and 5-(hept-6-hydroxy-4-enyl)-8-methylindolizidine ( 251B ). FTIR spectral analyses distinguish cis- and trans-decahydroquinolines and provide evidence for configurations of indolizidines.

Decahydroquinoline alkaloids: Noncompetitive blockers for nicotinic acetylcholine receptor-channels in pheochromocytoma cells andTorpedo electroplax

In pheochromocytoma PC12 cells, (+)-cis-decahydroquinoline 195A (5-methyl-2-propyl-cis-decahydroquinoline) and (+)-perhydro-cis-decahydroquinoline 219A (2,5-dipropyl-cis-decahydroquinoline) inhibit carbamylcholine-elicited sodium flux with IC50 values of 1.0 and 1.5 μM, respectively. Both of these decahydroquinolines appear to enhance desensitization, although apparent lack of complete removal of (+)-perhydro-cis-219A by washing complicates interpretation of the effects of that agent. A series of cis- and trans-decahydroquinolines with substituents in the 2- and 5-position also exhibit structure-dependent inhibition of carbamylcholine-elicited sodium flux in PC12 cells and all of the decahydroquinolines inhibit binding of the noncompetitive blocking agent [3H]perhydrohistrionicotoxin to muscle-type nicotinic acetylcholine receptor-channels in membranes fromTorpedo electroplax. The Ki values in electroplax membranes range from 1.4 to 7.9 μM, making these alkaloids comparable in potencies to the histrionicotoxins. Potencies are increased 2- to 3-fold in the presence of an agonist, carbamylcholine. The profile of activities are similar in PC12 cells and electroplax membranes. The cis- and trans-decahydroquinolines represent another class of noncompetitive blockers for acetylcholine receptor-channels with similar activity for both muscle-type and ganglionic type nicotinic receptors.

Applanoxidic acids A, B, C and D, biologically active tetracyclic triterpenes from Ganoderma applanatum

Abstract Four novel polyoxygenated lanostanoid triterpenes, named applanoxidic acids A, B, C, and D, have been isolated from an Indonesian tropical fungus, Ganoderma applanatum. Their structures were determined by spectrocopic and chemical methods. Biological activity as an anti-tumour promoter was observed for these components.

5,8-disubstituted indolizidines: a new class of noncompetitive blockers for nicotinic receptor-channels.

A series of 8-methyl-5-substituted indolizidines inhibit binding of the noncompetitive blocking agent [3H]perhydrohistrionicotoxin to muscle-type nicotinic acetylcholine receptor-channels in membranes fromTorpedo electroplax. The Ki values range from 0.16 to 1.12 μM, making these alkaloids among the most potent ligands for this site. Unlike most noncompetitive blockers, the potencies of the 8-methyl-5-substituted indolizidines arereduced in the presence of carbamylcholine. Indolizidine 205A (8-methyl-5-(4-pentynyl)indolizidine) is unique in enhancing binding of [3H]perhydrohistrionicotoxin by 1.5-fold. The enhancement is at a maximum at 0.01 to 0.1 μM, followed by progressive inhibition with an IC50 of about 20 μM. In the presence of carbamylcholine, which itself enhances binding of [3H]perhydrohistrionicotoxin, indolizidine 205A causes only an inhibition of binding with an IC50 of about 10 μM. Indolizidines with a hydroxy substituent on the 8-methyl group have very low activity. None of the indolizidines affect binding of [125I]α-bungarotoxin to acetylcholine recognition sites. In pheochromocytoma PC12 cells, indolizidine 205A has no agonist activity, but only inhibits carbamylcholine-elicited22Na+ influx. The profile of potencies for the 8-methyl-5-substituted indolizidines is similar in electroplax membranes and PC12 cells. Indolizidines 205A and 209B (8-methyl-5-pentylindolizidine) have no apparent effect on desensitization of receptors in PC12 cells. The 5,8-disubstituted indolizidines appear to represent an atypical and potent class of noncompetitive blockers for muscle-type and ganglionic nicotinic receptor-channels.

Malonate half-esters of homolanostanoid from an asian Ganoderma fungus

Abstract From the fruit body of an Indonesian Ganoderma species (Polyporaceae), malonic acid half-esters of two new homolanostanoid triterpene hydroxyacids have been isolated along with carboxyacetylquercinic acid, and characterized as their methyl esters. The stereochemistry of carboxyacetylquercinic acid was established by the X-ray crystallography of its methyl ester, and the structures of the two new components were determined by spectral analysis and comparisons with the methyl ester of carboxyacetylquercinic acid. An anti-tumour promoting activity of these quercinic acid derivatives is also reported.

Identification of histrionicotoxins by GC-MS and GC-FTIR: Photo- and chemical-artefacts and revised 13C NMR assignments

Abstract GC-mass and CG-FTIR spectral data together permit the rapid identification of the histrionicotoxin (HTX) alkaloids. 13C-NMR chemical shifts (δc) are reported for HTX 235A and revised δc are tabulated for nine HTXs and a perhydro-derivative. A butylboronic acid HTX derivative offers GC-MS and GC-FTIR advantages. Artefactural trans diene photoisomers of the HTX class are described as are formaldehyde condensation products. Two new HTX alkaloids 261 and 265E, are characterized by mass and FTIR spectra.