Chemotaxonomic features associated with flavonoids of cannabinoid-free cannabis (Cannabis sativa subsp. sativa L.) in relation to hops (Humulus lupulus L.)

The major flavonoids present in the leaves and flowers of the cannabinoid-free cannabis (Cannabis sativa subsp. sativa L.) cultivars Felina and Futura are orientin (1), vitexin (2), luteolin-7-O-beta-D-glucuronide (3), and apigenin-7-O-beta-D-glucuronide (4), while prenylated flavonoids, to which the potent estrogenicity of hops (Humilus lupulus L.) is associated, are absent. The different composition of flavonoids has chemotaxonomic value.     

Congresses,Conferences, Symposia,Meetings, and Seminars in the Field of Chemical Sciences held in 1995–1996

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Congresses, Conferences, Symposia, Meetings, and Seminars in the Field of Chemical Sciences held in 1995–1996     

Oil core-polymer shell microcapsules prepared by internal phase separation from emulsion droplets. I. Characterization and release rates for microcapsules with polystyrene shells

Microcapsules with an oil core surrounded by a polymeric shell have been prepared by the controlled phase separation of polymer dissolved within the oil droplets of an oil-in-water emulsion. The dispersed oil phase consists of the shell polymer (polystyrene), a good solvent for the polymer (dichloromethane), and a poor solvent for the polymer (typically hexadecane). Removal of the good solvent results in phase separation of the polymer within the oil droplets. If the three interfacial tensions between the core oil, the shell-forming polymer, and the continuous phase are of the required relative magnitudes, a polymer shell forms surrounding the poor solvent. A UV-responsive organic molecule was added to the oil phase, prior to emulsification, to investigate the release of a model active ingredient from the microcapsules. This molecule should be soluble in the organic core but also have some water solubility to provide a driving force for release into the continuous aqueous phase. As the release rate of the active ingredient is a function of the thickness of the polymeric shell, for controlled release applications, it is necessary to control this parameter. For the preparative method described here, the thickness of the shell formed is directly related to the mass of polymer dissolved in the oil phase. The rate of volatile solvent removal influences the porosity of the polymer shell. Rapid evaporation leads to cracks in the shell and a relatively fast release rate of the active ingredient. If a more gentle evaporation method is employed, the porosity of the polymer shell is decreased, resulting in a reduction in release rate. Cross-linking the polymer shell after capsule formation was also found to decrease both the release rate and the yield of the active ingredient. The nature of the oil core also affected the release yield.     

Direct probing of zwitterion formation in unsolvated peptides

Molecular beam electric deflection measurements have been used to determine electric susceptibilities for small unsolvated alanine-based peptides. The electric susceptibility provides information about the charge distribution within the peptide and can be used to distinguish between zwitterionic and canonical forms. Measured electric susceptibilities for WAn peptides (n = 1-5) are similar to those for capped Ac-WAn-NH2 peptides (which cannot form zwitterions). Susceptibilities calculated using a simulated tempering-based approach are substantially larger for the zwitterionic form than for the canonical form. The measured susceptibilities are in good agreement with those calculated for the canonical form. For the larger peptides, the lowest potential energy structure found in the simulations is hairpin-like, while the lowest free energy structure found at room temperature is extended. The zwitterionic form is constrained by intramolecular interactions which make it entropically unfavorable.     

Anisotropic local motions and location of amide protons in proteins

A new method has been developed to obtain dynamic and structural information about peptide planes in proteins by a combination of measurements of weak short-range cross-correlation rates R(H(N)N/NC') that are due to concerted fluctuations of the H(N)-N and N-C' dipole-dipole interactions and stronger long-range cross-correlation rates R(C'H(N)/H(N)N) and R(NH(N)/H(N)C(alpha)). The rates were interpreted using the axially symmetric Gaussian axial fluctuation model (GAF). The oscillation amplitudes as well as the positions of H(N) atoms with respect to peptide planes in ubiquitin were determined. Most N-H(N) bonds were found not to lie exactly along the bisector of the N-C' and N-C(alpha) bonds but to be slightly tilted toward the carbon-terminal side of the peptide.     

Facile Preparation of (±)-12-Epiprostaglandins from 7-Oxabicyclo[2.2.1]hept-5-en-2-one via an all-cis-formyllactone related to Corey lactone

The bicyclic monoselenoacetal 7 , easily obtained from (±)-7-oxabicyclo[2.2.1]hept-5-en-2-one ( 6 ) via a radical addition-acyl migration sequence, was converted to racemic 12-epiprostaglandins 3 and 4 . The key intermediate was the all-cis-formyllactone 2b related to Corey lactone (see 12 ; Scheme 1). The presence of a (tert-butyl)-dimethylsilyl protective group for the 11-OH substituent (prostaglandin numbering) was found to be crucial in avoidingβ -elimination and epimerization during the Wittig-Horner reaction (Scheme 2). Epimerization at C(12) at the formyllactone stage (see 2b ) was also possible and gave the known precursor 1b of naturally occurring prostaglandins and analogs.     

Countercurrent chromatographic isolation of lolitrem B from endophyte-infected ryegrass (Lolium perenne L.) seed

This paper describes a new method of purification of the Lolitrem B, a tremorgenic mycotoxin produced in planta by the endophytic fungus Neotyphodium lolii. The method is based on the large-scale isolation of the toxin by countercurrent chromatography (CCC). The lolitrem B content in endophyted ryegrass seed, 11 microg/g or 11 ppm, is extracted by stirring finely ground seeds with ethanol for 3 h at room temperature. The concentrated crude extract contains about 0.6 mg/g or 600 ppm of lolitrem B. It is then submitted to CCC purification with a biphasic four-solvent liquid system. A 160-fold enrichment was obtained in one step producing a raffinate containing 10% or 100 mg/g of the toxin. Further purifications were then performed by thin layer and low pressure liquid chromatography. Twenty-eight micrograms of lolitrem B with a 96% purity grade were obtained from 8 kg of seeds (yield 32%).     

Formation et réactivité de carbanions α phosphoramides. Mise en évidence d'une nouvelle réaction d'élimination

The reactivity of (diethoxy)-N-methyl-N-benzyl phosphoramide (I) and bis(dinethylamino)-N-methyl-N-benzylphosphoramide (II) when treated with strong bases (RLi, R₂NLi) is very different: (I) gives a novel elimination, whereas (II) under the same experimental conditions gives a stable carbanion whose reactivity has been investigated.     

POLARIZED OPTICAL PROPERTIES OF PHYCOBILISOMES FROM Anabaena, Nostoc and Synechococcus

Polarized absorption, photoacoustic, fluorescence excitation and fluorescence emission spectra of phycobilisomes were measured when embedded in polyvinyl alcohol films. The phycobilisomes were isolated from the following organisms: Anabaena cylindrica, Nostoc punctiforma and Synechococcus elongatus. The ratio of photoacoustic spectra to absorption was taken as a measure of thermal dissipation of excitation energy. The isotropic samples and those oriented by the film stretching were investigated. The stretching of the sample strongly influences the efficiency of excitation energy transfer occurring among biliproteins in phycobilisomes, as is seen from the dramatic changes in the fluorescence and thermal dissipation spectra. The effect of stretching the film depends on the shape of phycobilisomes and on the strength of interactions between biliproteins in phycobilisomes.     

The [CH2CHOH.+, CH3CHO] solvated enol radical cation

The bimolecular reaction of the CH₂CHOH^.+ enol ion (m/z 44) with acetaldehyde gives a strongly dominant product,m/z 45, formed mainly by proton transfer from the ion to the molecule. The abundance of the product coming from a H^. abstraction reaction from the neutral, albeit more exothermic, is negligible. In order to explain this result, the long lived [CH₂CHOH^.+, CH₃CHO] solvated ion was generated by reaction of the CH₂CHOH^.+ enol ion with (CH₃CHO) _n in the cell of a Fourier transform ion cyclotron resonance mass spectrometer. The structure of this solvated ion was clearly established. Labeling indicates that [CH₂CHOH^.+, CH₃CHO], upon low energy collisions, reacts by H^. abstraction more rapidly than by H⁺ transfer to the neutral moiety. This shows that the entropic factors are determinant when the enol ion reacts directly with acetaldehyde.