Identification of a New Antibacterial Sulfur Compound from Raphanus sativus Seeds.

Raphanus sativus L. (radish), a member of Brassicaceae, is widely used in traditional medicine in various cultures for treatment of several diseases and disorders associated with microbial infections. The antibacterial activity of the different plant parts has been mainly attributed to several isothiocyanate (ITC) compounds. However, the low correlation between the ITC content and antibacterial activity suggests the involvement of other unknown compounds. The objective of this study was to investigate the antibacterial potential of red radish seeds and identify the active compounds. A crude ethanol seed extract was prepared and its antibacterial activity was tested against five medically important bacteria. The ethanol extract significantly inhibited the growth of all tested strains. However, the inhibitory effect was more pronounced against Streptococcus pyogenes and Escherichia coli. Bioassay-guided fractionation of the ethanol extract followed by HPLC, 1H-NMR, 13C-NMR, 15N-NMR, and HMBC analysis revealed that the active fraction consisted of a single new compound identified as [5-methylsulfinyl-1-(4-methylsulfinyl-but-3-enyl)-pent-4-enylidene]-sulfamic acid, which consisted of two identical sulfur side chains similar to those found in ITCs. The minimal inhibitory concentration values of the isolated compound were in the range of 0.5-1 mg/mL. These results further highlight the role of radish as a rich source of antibacterial compounds.

NMR-based screening of membrane protein ligands.

Membrane proteins pose problems for the application of NMR-based ligand-screening methods because of the need to maintain the proteins in a membrane mimetic environment such as detergent micelles: they add to the molecular weight of the protein, increase the viscosity of the solution, interact with ligands non-specifically, overlap with protein signals, modulate protein dynamics and conformational exchange and compromise sensitivity by adding highly intense background signals. In this article, we discuss the special considerations arising from these problems when conducting NMR-based ligand-binding studies with membrane proteins. While the use of (13)C and (15)N isotopes is becoming increasingly feasible, (19)F and (1)H NMR-based approaches are currently the most widely explored. By using suitable NMR parameter selection schemes independent of or exploiting the presence of detergent, (1)H-based approaches require least effort in sample preparation because of the high sensitivity and natural abundance of (1)H in both, ligand and protein. On the other hand, the (19)F nucleus provides an ideal NMR probe because of its similarly high sensitivity to that of (1)H and the lack of natural (19)F background in biologic systems. Despite its potential, the use of NMR spectroscopy is highly underdeveloped in the area of drug discovery for membrane proteins.

Parallel synthesis of arrays of amino-acid-derived isocyanoamides useful as starting materials in IMCR.

Arrays of amino-acid-derived isocyanoamides are conveniently produced on a multigram scale in one step by the solventless aminolysis of the corresponding methyl esters with primary or secondary aliphatic amines. Most of the corresponding isocyanides precipitate during the reaction and can be filtered to yield highly pure, colorless, and odorless solids. They are potentially useful in the combinatorial chemistry of multicomponent reactions.

Total Synthesis of Uvaricin.

The first total synthesis of naturally occurring (+)-uvaricin was achieved using three consecutive Sharpless asymmetric dihydroxylation (AD) reactions to place the necessary oxygen functions on a "naked" carbon skeleton in a regio- and enantioselectively controlled manner. The appropriate bis-THF ring system was constructed using a Williamson type etherification reaction on a functionalized bis-mesylate intermediate.