Bioactive alkaloids from Brunsvigia radulosa.

A phytochemical investigation of the bulbs of Brunsvigia radulosa yielded the new alkaloid 1-O-acetylnorpluviine, together with the known structures 1-epideacetylbowdensine, crinamine, crinine, hamayne, lycorine, anhydrolycorin-6-one and sternbergine. All structures were established by spectroscopic evidence. Some of the 13C assignments which were reported for crinamine and hamayne were corrected by means of 2D NMR techniques. In order to provide a further structure for biological testing, crinamine was converted to apohaemanthamine. The alkaloids were tested for activity against two strains of cultured Plasmodium falciparum and for cytotoxicity with BL6 mouse melanoma cells.

Cytotoxic and antimalarial alkaloids from Brunsvigia littoralis.

Four known alkaloids, lycorine (1), 1,2-di-O-acetyllycorine (2), ambelline (3), and crinine (4) were isolated from the bulbs of Brunsvigia littoralis (Amaryllidaceae). 1H- and 13C-NMR spectra of 2 were completely assigned by means of 1D- and 2D-NMR techniques. The alkaloids (1-4) together with the synthesised 11-O-acetylambelline (3a) and 3-O-acetylcrinine (4a) were tested for antimalarial activity with two strains of cultured Plasmodium falciparum and for cytotoxicity with BL6 mouse melanoma cells. Structures 1 and 2 exhibited both antimalarial and cytotoxic activity.

Composition and antimalarial activity in vitro of the essential oil of Tetradenia riparia.

The essential oil from the leaves and stems of Tetradenia riparia was analysed by GC and GC/MS and 35 components were identified. The main constituents were alpha-terpineol (22.6%), fenchone (13.6%), beta-fenchyl alcohol (10.7%), beta-caryophyllene (7.9%), and perillyl alcohol (6.0%). Moderate antimalarial activities were recorded against two strains of Plasmodium falciparum.

Structures of the glycopeptidolipid antigens of serovars 25 and 26 of the Mycobacterium avium serocomplex, synthesis of allyl glycosides of the outer disaccharide units and serology of the derived neoglycoproteins.

The pentasaccharide hapten released from the glycopeptidolipid (GPL) antigen of M. avium serovar 26 has been characterized as O-(2,4-di-O-methyl-alpha-L-fucopyranosyl)-(1-->4)- O-beta-D-glucopyranosyluronic acid-(1-->4)-O-(2-O-methyl-alpha-L-fucopyranosyl)-(1-->3)-alpha-L- rhamnopyranosyl-(1-->2)-6-deoxy-L-talose. The allyl glycosides of the outer glycosyl and glycobiosyl units of this hapten have been synthesized, the latter by a route involving oxidation of the corresponding D-glucopyranose derivative. Conjugation of allyl glycosides to protein by ozonolysis and reductive coupling afforded neoantigens (neo 26-1 and 26-2), both of which interacted with antibodies to M. avium serovar 26. The terminal sugar residue of the pentasaccharide hapten of the serovar 25 GPL had been shown to have the galacto configuration on the basis of 1H-13C NMR correlation spectroscopy, but absolute configurational assignment for the sugar awaited the synthesis, as for neo 26, of two glycobiosyl NGPs bearing the terminal sugar in the D and L enantiomeric forms, respectively. Only the glycobiosyl NGP bearing the terminal sugar as the D-enantiomer interacted with antibodies to M. avium serovar 25, thus providing evidence for the absolute configuration of the sugar, and showing that the complete oligosaccharide hapten has the structure, O-(4-acetamido-4,6-dideoxy-2-O-methyl-alpha-D- galactopyranosyl)-(1-->4)-O-beta-D-glucopyranosyluronic acid-(1-->4)-O-(2-O-methyl-alpha-L-fucopyranosyl)-(1-->3)-O-alpha-L- rhamnopyranosyl-(1-->2)-6-deoxy-L-talose.

Synthesis of allyl glycosides for conversion into neoglycoproteins bearing epitopes of mycobacterial glycolipid antigens.

Neoglycoproteins bearing key glycosyl substituents of several glycopeptidolipid antigens of pathogenic Mycobacterium species have been synthesized. Allyl glycosides of the terminal 6-deoxyhexose-containing units of the antigens were prepared, with appropriate ether and ester substituents in place. Ozonolysis of the allyl glycosides was then followed by reductive coupling with epsilon-amino groups of lysine residues in bovine serum albumin, using sodium cyanoborohydride at pH 7.8. The resulting neoglycoproteins emulated the antigenicity of the native molecule in several serological tests.

Correlations between in vitro and in vivo mechanisms of pyrethroid insecticide action.

Classical neuropharmacological procedures have been used to elucidate insecticide mode of action in vitro. A good deal has thus been learned about pyrethroids but novel techniques have been necessary to explain the toxicology and symptomology. The free-walking, electrode-implanted cockroach technique, which was developed for this purpose, is described. It enabled correlations to be made between symptomology and effects on specific nerves. The negative temperature coefficient of toxicity of allethrin (the first pyrethroid) was explained in terms of repetitive firing in peripheral (sensory) nerves rather than by nerve blockage, which had been suggested from previous in vitro studies. The elucidation of target sites in vivo and the most useful parameter to study, i.e., repetitive firing in nerve axons, enabled the definition of a pyrethroid resistance mechanism in a major insect pest. It also showed two modes of action for permethrin and cypermethrin, its alpha-cyano analog. A structure-activity relationship for a range of pyrethroids, combining in vitro and in vivo approaches, confirmed two distinct types of pyrethroid action. Studies of poisoning signs and nerve disruptions in vivo in the mouse and cockroach, using diazepam in conjunction with pyrethroids, implicated the GABA-receptor complex as a target for alpha-CN-phenoxybenzyl pyrethroids. This was confirmed by making conductance measurements in crayfish claw opener muscle fibers in vitro.

A new pyrethroid insecticide with remarkable potency on nerve axons.

The analog of cis-tetramethrin with a 2,2-dimethyl-cyclopropyl replacement for the 2-methyl-1-propenyl group, i.e., "methanotetramethrin", is one of the most neuroactive compounds ever described. It is 10(3)- to greater then 10(5)-fold more potent than tetramethrin in inducing repetitive firing following stimulation in a cockroach cercal sensory nerve in vitro, and the repetitive firing is considerably more persistent. Also, it is more toxic to the cockroach and the housefly. The remarkable potency of methanotetramethrin, giving consistent repetitive firing in this nerve assay at 10(-18) M, and the speculation that it may undergo reversible covalent binding via Michael addition indicate that it could be a useful neurophysiological probe and candidate affinity label for the sodium channel.