Two new xanthone glycosides, corymbiferin 3-O-beta-D-glucopyranoside (1) and swertiabisxanthone-I 8'-O-beta- d-glucopyranoside (2), were isolated from Gentianella amarella ssp. acuta, along with eight known xanthones: triptexanthoside C, veratriloside, corymbiferin 1-O-glucoside, swertianolin, norswertianolin, swertiabisxanthone-I, bellidin, and bellidifolin, four of them identified for the first time in G. amarella ssp. acuta. The isolation was conducted mainly by centrifugal partition chromatography, and the structures of the isolated compounds were established on the basis of spectrometric data including 2D NMR and mass spectrometry. Xanthones were weakly active against acetylcholinesterase (AChE), except triptexanthoside C, which inhibited AChE with an IC(50) of 13.8 +/- 1.6 microM. Some compounds were active against monoamine oxidases (MAO): bellidin and bellidifolin showed interesting inhibitory activity of MAO A, while swertianolin, the 8-O-glucopyranoside form of bellidifolin, gave 93.6% inhibition of MAO B activity at 10(-5) M.

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Diblock copolymers were prepared by condensation of benzoyl-terminated poly(p-benzamide) [PhCO(PBA)] and anilino-terminated poly(m-phenylene isophthalamide) [PhNH(MPD-I)]. The copolymers were freed from unreacted prepolymers and also partially fractionated by selective extraction techniques. The formation of the nematic phase was investigated for three copolymers having a similar length of the rigid PhCO(PBA) block and a fraction β of flexible segment covering a range from 0.5 to 0.7. In the N,N-dimethylacetamide (DMAc) containing 3% LiCl solvent the critical volume fraction v 2 i of the PhCO(PBA) prepolymer was largely unaffected by copolymerization with a similar length of the flexible PhNH(MPD-I) block. At the largest β value only a 25% increase in the critical composition of PhCO(PBA) was observed. The mesophase appears capable of admitting much longer flexible sequences than anticipated. These results are qualitatively in line with a reduced flexibility of the flexible segment due to the self-consistent orientational field of the mesophase. However, comparison of data in aggregating and nonaggregating solvents suggests that mesophase formation should be described in terms of supramolecular assemblies rather than molecularly dispersed units.