A comprehensive view on 4-methyl-2-quinazolinamine, a new microbial alkaloid from Streptomyces of TCM plant origin.

In the course of our chemical and biological screening program for yet unidentified microbial metabolites, we selected plants of Traditional Chinese Medicine (TCM) as habitats for talented Streptomycetes producer strains for the first time. Liquid pure cultures of strain Streptomyces sp. GS DV232 were found to contain 4-methyl-2-quinazolinamine (1), a potent alkaloid yet unknown from nature. In this study, we investigated the chemical and crystal structure of 1, as well as its antiproliferative bioactivity, and addressed the unusual biosynthesis using feeding experiments.

Infrared spectroscopy of acetic acid and formic acid aerosols: pure and compound acid/ice particles.

Acetic acid aerosol particles, formic acid aerosol particles and mixed acid/ice particles were generated in a collisional cooling cell at a temperature of 78 K and investigated using in situ rapid scan Fourier transform infrared spectroscopy. The infrared spectra reveal that the internal structure of the particles critically depends on the particle formation conditions and, especially for the mixed particles, on the composition. The acetic acid particles are likely to have only a partially crystalline structure whereas the formic acid particles are likely to have an overall crystalline structure. The existence of acid in the mixed acid/ice particles prevents the ice from crystallization even at low acid concentrations (less than 10%). Mid-infrared refractive index data were derived from the different particle spectra, which can be helpful for remote sensing of such systems.

Biosynthetic origin of the methoxyl extender unit in bafilomycin and concanamycin using stereospecifically labeled precursors.

The microbial macrolides bafilomycin A1, B, and concanamycin A from Streptomyces spp. are potent and specific inhibitors of V-ATPases. The question of the biosynthetic origin of the two uncommon "glycolate units" of each of the macrolide structures was addressed by feeding experiments with stereospecifically 13C-labeled precursors. Our studies clearly indicate that glycerol is a source for the methoxylated C2-units and determines the orientation of the incorporation. Products from the carboxylic acid pool or TCA cycle are ruled out as key precursors. The data suggest the action of a glycerol kinase and point to phosphoglycerate as an intermediate in their biosynthesis. However, glycerate itself is not accepted as a precursor. We present the likely biosynthetic pathway and show the value of stereospecifically labeled presursors as an important tool for biosynthetic investigations.