Sugar composition of the moss Rhodobryum ontariense (Kindb.) Kindb

Although the second biggest terrestrial group of plants, bryophytes remain poorly known chemically compared to the angiosperms. In this article, the sugars of the moss Rhodobryum ontariense, an unstudied representative of the medicinally known genus, are reported. The chemical analysis revealed the usual plant sugar sucrose, and a new sugar, fructooligosaccharide 1-kestose, which is reported first not only for the genus Rhodobryum, but also for mosses. The trisaccharides have been scantily reported in bryophytes hitherto. This gives more significance to this study for further investigation of its role in the moss species. The health-promoting effect of 1-kestose is also briefly discussed.     

Mass spectrometric study of some 4-pyrimidine carboxylic acids

Mass spectrometry has been applied in order to study the main fragmentation routes of some 4-pyrimidene carboxylic acids. Differences in fragmentation were caused by the nature of the substituent in position 2 of the pyrimidine ring, while the methyl group in position 1, 3 or 6 did not influence the fragmentation route.     

Composition and antimicrobial activity of Seseli globiferum essential oil

The essential oil from aerial parts of Seseli globiferum Vis. obtained by hydrodistillation with Clevenger-type apparatus was analyzed by GC-MS. Twenty-eight compounds were identified, representing 99.4% of the total oil. The main components of the oil were sabinene (38.0%), alpha-pinene (21.2%) and beta-phellandrene (13.5%). The microbial growth inhibitory properties of the isolated essential oil were determined using the broth microdilution method against seven bacterial species: Salmonella typhimurium (ATCC 13311), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), Enterobacter cloacae (clinical isolates), Bacillus cereus (clinical isolates), Staphylococcus aureus (ATCC 25923), Staphylococcus epidermidis (ATCC 12228), Micrococcus flavus (ATCC 10240) and three fungal species: Aspergillus niger (ATCC 6275), Aspergillus versicolor (ATCC 11730), Trichoderma viride (IAM 5061) and Penicillium funiculosum (ATCC 36839). The essential oil showed activity against bacteria P. aeruginosa, followed by M flavus, L. monocytigenes and E. coli, and all investigated fungal species.     

Conformational Analysis of Guaianolide-Type Sesquiterpene Lactones by Low-Temperature NMR Spectroscopy and Semiempirical Calculations

Conformational analysis of 9-acetoxycumambrine A 1 and 8-O-isobutiryl-9-acetoxycumambrine B 2 was carried out by low-temperature NMR studies. Results suggested that lactones 1 and 2 are mixtures of two distinctive conformers, I and II. Based on low-temperature ¹H NMR spectra, in four solvents, the thermodynamic parameters of I II exchange process were assessed. Energy of activation of I II reaction was obtained by dynamic NMR simulations for both compounds. Results revealed that conformational exchange of lactones 1 and 2 occurs due to chair twisted chair interconversion of a heptane ring. The same PM3 semiempirical method was applied for geometry optimization of lactones 1 and 2, as well as of 9-hydroxycumambrine A 3, 9-acetoxycumambrine B 4, and cumambrine B 5.     

Stereochemistry and conformations of natural 1,2-epoxy-guaianolides based on 1D and 2D NMR data and semiempirical calculations

From detailed study of 1D and 2D NMR spectra of ten natural 1,2-epoxyguaianolides (bis-1,2:3,4-epoxyguaianolides and guaianolide-1,2-epoxychlorohydrins), we identified general spectral traits helpful for stereochemical assignment of such sesquiterpene lactones. We found that the chemical shifts of certain (1)H and (13)C nuclei are consistently dependent on the configuration of 1,2-epoxy-ring which could be used as a simple rule for establishing this configuration. Then, from 1D and 2D (COSY, NOESY, HMQC, HMBC) NMR data, applying the observed rule, the structure and stereochemistry of two new, diastereomeric guaianolide-1,2-epoxychlorohydrins, isolated from Achillea serbica, are determined. The NMR data, namely, nuclear overhauser enhancement (NOE) correlations, pointed out two conformations of guaianolide's cycloheptane ring. The semiempirical calculations (AM1 and PM3 methods), performed in order to gain additional information regarding conformations, resulted in three geometries of investigated lactones. Even so, the conformations derived from the NMR data agreed well with those calculated by semiempirical methods.