Antimycobacterial flavones from Haplopappus sonorensis.

Crude extracts of Haplopappus sonorensis (A. Gray) S.F. Blake (Asteraceae), showed activity against Mycobacterium tuberculosis H(37)Rv. By assay-guided fractionation, 5-hydroxy-3,7,4'-trimethoxyflavone (1). 5,7-dihydroxy-3,4'-dimethoxyflavone (2). and 5,4'-dihydroxy-3,7-dimethoxyflavone (3). were identified as the antimycobacterial principles. Compound 2 was the most active compound.

Intramolecular homolytic substitution at selenium: synthesis of novel selenium-containing vitamin E analogues.

Treatment of 1-(benzylselenenyl)-5-butyl-5-nonanol (10) with oxalyl chloride followed by the sodium salt of N-hydroxypyridine-2-thione afforded the corresponding pyridine-2-thione-N-oxycarbonyl (PTOC) oxalate ester which was not isolated but immediately heated to provide 2,2-dibutylselenane (7). This transformation presumably involves a tertiary alkyl radical that undergoes intramolecular homolytic substitution at selenium with loss of the benzyl radical to provide the selenium-containing ring system (7). A similar protocol, when applied to 1-(2-benzylselenenyl-5-methoxyphenyl)-3-methyl-3-heptanol (18) and 1-(2-benzylselenenyl-5-methoxyphenyl)-3,7,11,15-tetramethyl-3-hexadecanol (19), followed by deprotection, afforded the selenium-containing alpha-tocopherol analogues 4 and 1f, respectively, in moderate yields. To the best of our knowledge, these transformations represent the first examples of tertiary radicals involved in homolytic substitution chemistry at selenium.

Recording properties and biocompatibility of chronically implanted polymer-based intrafascicular electrodes.

We implanted polymer-based longitudinal intrafascicular electrodes (polyLIFEs) in feline dorsal rootlets acutely and for periods of two to six months to evaluate their electrical properties and biocompatibility. A total of 38 implanted electrodes were analyzed. Some 25 of the 38 electrodes were implanted with an insulative flexible polymer cuff, which was required for recording of afferent activity in situ. Electrode impedances remained stable for the duration of the experiments. The distributions of axons were measured at three levels of the implanted rootlets: the implant level, 1-2 mm proximal to the implant with respect to the cell body, and 1-2 mm distal to the implant with respect to the cell body. Similar measurements were made in five samples of fascicles neighboring an implant and six samples of control tissue from animals in which no implants were placed. The polyLIFEs demonstrated a high degree of biocompatibility, as no adverse effects on axon size were observed in either the implanted fascicle or neighboring neural tissue. However, the insulative cuffs were found to be a source of compression, resulting in necrosis of the neural tissue.