Covalent anthocyanin-flavone dimer from leaves of Oxalis triangularis.

The anthocyanin-flavone C-glycoside, (malvidin 3-O-(6(II)-O-alpha-rhamnopyranosyl(AIV)-beta-glucopyranoside(AII))-5-O-beta-glucopyranoside(AIII)) (apigenin 6-C-(2(II)-O-beta-glucopyranosyl(FIII)-beta-glucopyranoside(FII))) malonate(AV) (A(IV)-4-->A(V)-1, F(III)-6-->A(V)-3) (1), has been isolated from leaves of Oxalis triangularis A. St.-Hil. In the 1D (1)H NMR spectrum of 1 dissolved in CD(3)OD-CF(3)CO(2)D (95:5), MTFA, recorded 45 min after sample preparation, this covalently linked dimer occurred mainly as flavylium cation (38%) and two equilibrium forms assigned to be quinonoidal bases (54%), whereas only minor amounts of the hemiacetal forms were present. After five days storage at 300 K, the hemiacetals (39%) and flavylium cation (38%) constituted the main forms of 1. More simple anthocyanins are normally considered to be on the flavylium cation form in acidified deuterated methanol. The cross-peaks observed in NOESY NMR spectra of 1 indicated the presence of vertical 'pi-pi' stacking between the B-ring of the flavone unit and the A-ring of each of the two forms assigned to be quinonoidal bases. It was not possible to discriminate between inter- or intramolecular association mechanisms. The equilibria between the various forms of 1 were studied by two-dimensional NOESY and ROESY NMR spectroscopy. 2D HSQC-TOCSY NMR spectroscopy was among the methods used for characterization of the various forms.

Acylated anthocyanins from leaves of Oxalis triangularis.

The novel anthocyanins, malvidin 3-O-(6-O-(4-O-malonyl-alpha-rhamnopyranosyl)-beta-glucopyranoside)-5-O-beta-glucopyranoside (2), malvidin 3-O-(6-O-alpha-rhamnopyranosyl-beta-glucopyranoside)-5-O-(6-O-malonyl-beta-glucopyranoside) (3), malvidin 3-O-(6-O-(4-O-malonyl-alpha-rhamnopyranosyl)-beta-glucopyranoside)-5-O-(6-O-malonyl-beta-glucopyranoside) (4), malvidin 3-O-(6-O-(4-O-malonyl-alpha-rhamnopyranosyl)-beta-glucopyranoside) (5) and malvidin 3-O-(6-O-(Z)-p-coumaroyl-beta-glucopyranoside)-5-O-beta-glucopyranoside (6), in addition to the 3-O-(6-O-alpha-rhamnopyranosyl-beta-glucopyranoside)-5-O-beta-glucopyranoside (1) and the 3-O-(6-O-(E)-p-coumaroyl-beta-glucopyranoside)-5-O-beta-glucopyranoside (7) of malvidin have been isolated from purple leaves of Oxalis triangularis A. St.-Hil. In pigments 2, 4 and 5 a malonyl unit is linked to the rhamnose 4-position, which has not been reported previously for any anthocyanin before. The identifications were mainly based on 2D NMR spectroscopy and electrospray MS.

Alpha 2C-adrenoceptor mediated regulation of cortical EEG arousal.

Alpha2-adrenergic drugs modulate cortical arousal and EEG. However, the role of individual alpha2-adrenoceptor (alpha(2)-AR) subtypes in these functions is not clear. We investigated the role of alpha(2C)-ARs in the modulation of baseline cortical EEG activity and EEG responses to the alpha(2)-AR selective agonist, dexmedetomidine (3-300 microg/kg, s.c.), and antagonist, atipamezole (3-1000 microg/kg, s.c.), by using alpha(2C)-AR knockout (KO) and wildtype (WT) mice. The overall amplitude (1-30 Hz) was not significantly altered in KO mice although the activity of theta band (4-8 Hz) was increased in these mice. The main finding was that dexmedetomidine (30-300 microg/kg) more effectively slowed and atipamezole (30-1000 microg/kg) less effectively increased cortical EEG arousal in KO mice compared to WT controls. Importantly, autoradiographical results showed no compensatory increase in other alpha(2)-AR subtypes in cortical, thalamic or other brain structures of KO mice. Furthermore, there were no differences between the genotypes in the levels of hippocampal choline acetyltransferase, monoamines or their metabolites. Altered baseline cortical EEG activity and EEG responses to alpha(2)-AR selective drugs in KO mice indicate that alpha(2C)-ARs are involved in regulation of cortical arousal. These results suggest that alpha(2C)-ARs may antagonize the sedative effect of alpha(2)-AR agonists mediated by activation of alpha(2A)-ARs.