Characterization of proanthocyanidins from grape seeds.

Leucoselect (grape seed selected proanthocyanidins) was analyzed. HPLC thermospray mass spectrometry (TSP-MS) allowed the detection of monomeric flavan-3-ols and dimeric proanthocyanidins. Fractionation over Sephadex LH-20 resin and analysis of the isolated fractions by gel permeation chromatography (GPC) and electrospray mass spectrometry (ESI-MS) led to the complete characterization of the proanthocyanidin constituents of Leucoselect. The analysis revealed the presence of approximately 15% of (+)-catechin (1) and (-)-epicatechin (2), 80% of (-)-epicatechin 3-O-gallate (3), dimers, trimers, tetramers and their gallates and 5% of pentamers, hexamers, heptamers and their gallates.

Evaluation of an automatic gas chromatographic system for the identification of bacterial infective agents.

The potential clinical application of gas chromatography to microbial identifcation was evaluated. A completely automated system, the MIS (Microbial Identification System; Hewlett- Packard) can analyse and identify pure strains by comparison of their cellular fatty acids patterns (C(9)-C(20)) with the reference parameters stored in a library. Three hundred and sixty-seven strains were tested, comparing the gas chromatographic results with those obtained by the traditional microbiological methods in the bacteriology laboratory of our Institute. A standardized extractive procedure was followed to obtain the fatty acid methyl esters (FAMEs), but some modifications to the recommended procedure were introduced in the bacterial growth procedures: colonies harvested not only from the recommended growth media but also from selective media routinely used in the bacteriology laboratory were successfully examined. These modifications did not influence the results but improved the ease for the user; good agreement with the comparison method was observed as far as identifications of genus and species are concerned for 238 cases. The major advantages of this computerized system are a reduction in the time required to obtain the final results, the elimination of human errors by using the autosampler and a better inter-laboratory comparability of results owing to a higher degree of objectivity. On the other hand, the limited throughput of MIS (only 40 samples in 24 h) prevents its use in a large routine laboratory; this technology is appropriate in emergency cases, in taxonomic studies and as a confirmatory method.

Reduction of acetaldehyde to ethanol by some micro-organisms and its stereospecificity.

The stereochemical course of the reduction of acetaldehyde to ethanol was investigated by evaluating, with the enzymic system yeast alcohol dehydrogenase/diaphorase and g.c.-m.s., the configuration of [1-2H]ethanol obtained from [1-2H]acetaldehyde with different micro-organisms. Although only S-[1-2H]ethanol was formed, all the micro-organisms showed evidence of the existence of alcohol dehydrogenases with opposite stereospecificity.

Electron impact mass spectrometry of maleimycin.

The mass spectrometric behaviour of maleimycin, a bicyclic maleimide antibiotic, is discussed in detail with the aid of exact mass measurements, metastables (linked scans B/E and B2/E), ionization and appearance energy measurements and deuterium labelling experiments. The unusual loss of NH3 from the molecular ion is highlighted and a possible mechanism is proposed.