Antispasmodic Effect of Asperidine B, a Pyrrolidine Derivative, through Inhibition of L-Type Ca2+ Channel in Rat Ileal Smooth Muscle

Antispasmodic agents are used for modulating gastrointestinal motility. Several compounds isolated from terrestrial plants have antispasmodic properties. This study aimed to explore the inhibitory effect of the pyrrolidine derivative, asperidine B, isolated from the soil-derived fungus Aspergillus sclerotiorum PSU-RSPG178, on spasmodic activity. Isolated rat ileum was set up in an organ bath. The contractile responses of asperidine B (0.3 to 30 µM) on potassium chloride and acetylcholine-induced contractions were recorded. To investigate its antispasmodic mechanism, CaCl2, acetylcholine, Nω-nitro-l-arginine methyl ester (l-NAME), nifedipine, methylene blue and tetraethylammonium chloride (TEA) were tested in the absence or in the presence of asperidine B. Cumulative concentrations of asperidine B reduced the ileal contraction by ~37%. The calcium chloride and acetylcholine-induced ileal contraction was suppressed by asperidine B. The effects of asperidine B combined with nifedipine, atropine or TEA were similar to those treated with nifedipine, atropine or TEA, respectively. In contrast, in the presence of l-NAME and methylene blue, the antispasmodic effect of asperidine B was unaltered. These results suggest that the antispasmodic property of asperidine B is probably due to the blockage of the L-type Ca2+ channel and is associated with K+ channels and muscarinic receptor, possibly by affecting non-selective cation channels and/or releasing intracellular calcium.

Absolute structure of the chiral pyrrolidine derivative (2S)-methyl (Z)-5-(2-tert-butoxy-1-cyano-2-oxoethylidene)pyrrolidine-2-carboxylate, a compound with low resonant scattering

The enantiopure monopyrrolidine derivative (2S)-methyl (Z)-5-(2-tert-butoxy-1-cyano-2-oxoethylidene)pyrrolidine-2-carboxylate, C₁₃H₁₈N₂O₄, (1), represents a potential ligand and an attractive intermediate for the synthesis of chiral metal complexes. At the molecular level, the compound features an intramolecular N-H...O hydrogen bond; neighbouring molecules interact via N-H...N contacts to form chains along [100]. Due to its elemental composition, resonant scattering of the target compound is entirely insignificant for diffraction experiments with Mo Kα and small even for Cu Kα radiation. A preliminary study with the harder radiation type confirmed the chiral space group and the suitability of the single crystal chosen; as expected, the results concerning the absolute structure remained completely inconclusive. A second data collection with the longer wavelength gave satisfactory quality indicators for the correct handedness of the molecule, albeit with high standard uncertainties. The absolute configuration has been assessed independently: CD spectra for both enantiomers of the target molecule were calculated and the spectrum for the S-configured stereoisomer was in agreement with the experiment. The Cotton effect of (1) may be ascribed to π-π* transitions from HOMO to LUMO and from HOMO to LUMO+1. As both independent techniques agree with respect to the handedness of the target molecule, the absolute structure may be assigned with a high degree of confidence.

Crystal structure of 15-(2-chloro-phen-yl)-6b-hy-droxy-17-methyl-6b,7,16,17-tetra-hydro-7,14a-methanona-phtho[1',8':1,2,3]pyrrolo-[3',2':8,8a]azuleno[5,6-b]quinolin-14(15H)-one

In the title compound, C₃₄H₂₅ClN₂O₂, the fused pyrrolidine ring adopts an envelope conformation with the N atom as the flap. The two adjacent cyclo­pentane rings also adopt envelope conformations. The mean plane of the pyrrolidine ring makes dihedral angles of 40.53 (10) and 80.23 (10)° with the mean planes of the cyclo­pentane rings. The dihedral angle between the mean planes of the cyclo­pentane rings is 46.71 (9)°. An intra­molecular O—H⋯N hydrogen bond is observed. In the crystal, mol­ecules are linked by C—H⋯O, C—H⋯N and C—H⋯π inter­actions, forming a layer parallel to (10-2).