Novel cytotoxic, alkylated hydroquinones from Lannea welwitschii.

Two novel natural products, lanneaquinol (1) and 2'(R)-hydroxylanneaquinol (2), were isolated from the organic extract of the plant Lannea welwitschii (Hiern) Engl. Their structures were solved by spectroanalytical methods and confirmed by comparison to synthetic models. The absolute configuration of 2 was determined by the modified Mosher method. Both compounds exhibited modest cytotoxicity against the NCI panel of 60 human tumor cell lines. The structures of two isomeric 4,5-dihydroxy-5-alkyl-2-cyclohexenones (7 and 8), which appear to be biogenetic precursors of 1 and 2, were also elucidated.

Anticonvulsant efficacy of ADCI (5-aminocarbonyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine) after acute and chronic dosing in mice.

ADCI (5-aminocarbonyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5, 10-imine), a low-affinity uncompetitive N-methyl-D-aspartate (NMDA) antagonist, is a broad-spectrum anticonvulsant with a favorable side-effect profile. In the present study, we sought to determine if tolerance develops to the anticonvulsant activity of ADCI, using the maximal electroshock (MES) test to assess seizure protection. Mice were treated with three daily injections of a 2 x ED50 dose for MES protection (18 mg/kg, intraperitoneally, i.p.) or vehicle for 7 or 14 days. On the day after the chronic treatment protocol, all animals received a challenge dose of ADCI (18 mg/kg) and 15 min later were evaluated in the MES test. In control animals, 83-94% of animals were protected and the ADCI plasma levels immediately after the MES test were 5.5-9.7 micrograms/ml. In treated animals, 29 and 0% of animals were protected at 7 and 14 days, respectively, and the ADCI plasma levels were 77 and 52% of the control values. [3H]Dizocilpine binding to brain NMDA receptors was unaltered by the chronic drug treatment. In subsequent experiments, we determined that 14-day chronically treated animals could be completely protected by increased doses of ADCI (ED50 28.9 mg/kg). In both naive and chronically treated animals receiving a challenge dose of ADCI, plasma drug levels decreased in two phases, the first with a time constant of approximately 55 min and the second with a much slower rate. The estimated plasma concentrations of ADCI reflecting threshold (3-5 micrograms/ml) and 50% protection (5-7.5 micrograms/mg) were similar in naive and chronic animals.(ABSTRACT TRUNCATED AT 250 WORDS)

FAB-MS/MS spectrometry in determining the primary structure of gamma-glutamyl-containing peptides.

Positive fast atom bombardment tandem mass spectrometry (FAB-MS/MS) was applied for peptide sequencing, particularly for determining the gamma glutamyl linkage involved in metal-binding peptides such as Cadystin (gamma EC)3G = Cadystin A and Cadystin (gamma EC)2G = Cadystin B (MW 771 and 539, respectively). The fragmentation patterns between the natural gamma glutamyl peptide and the synthetic alpha glutamyl one were clearly distinguishable. FAB-MS/MS was proved to be a good method for determining these peptides, since it needed no chemical degradation and only a small amount of the peptide was needed for determination.

Mycotoxin analysis by fast atom bombardment tandem mass spectrometry.

Positive fast atom bombardment tandem mass spectrometry is demonstrated to be an effective technique for determination of crude aflatoxins and sterigmatocystin-related compounds. The molecular ion was selected by the first system and bombarded to produce characteristic daughter ions that could be used to identify mycotoxins in mixtures and with the same molecular weight.

Dyakia bioluminescence--1. Bioluminescence and fluorescence spectra of the land snail, D. striata.

The luminescent land snail Dyakia striata displayed a bioluminescence spectrum with a maximum wavelength of 515 nm. A green fluorescent substance extracted from the photogenic organ of an adult snail had a similar wavelength maximum but its fluorescence spectrum differed from that of flavin chromophore substances involved in light emission in some other luminescent organisms.

Lampteromyces bioluminescence--1. Identification of riboflavin as the light emitter in the mushroom L. japonicus.

The bioluminescence of the luminous mushroom, Lampteromyces japonicus, was studied by using the mushroom gills and also the luminous mycelia, the latter being cultured from the isolated spores and grown in a potato sucrose medium. The luminescence intensity of the mushroom gills and the cultured mycelia was measured in an aqueous suspension under various conditions. The original intensity was enhanced by exposing the luminous cells to oxygen for several hours or to acids or bases for a short period. This enhancement enabled measurement of their bioluminescence spectra which were identical to the fluorescence spectrum of riboflavin, having a maximum at 524 nm. The green fluorescent substance was extracted with cold water from the mushroom and it was identified as riboflavin by spectroscopic and chromatographic analyses. Riboflavin was concluded to be the light emitter of this mushroom.