Benzopyranones and their sulfate esters from Pelargonium sidoides.

Investigation of the benzopyranones from the roots of PELARGONIUM SIDOIDES led to the identification of 15 benzopyranones, among them the novel compounds 12 and 14. Furthermore, benzopyranones 4 and 15 were detected in PELARGONIUM SIDOIDES for the first time. Structure determinations were performed by one- and two-dimensional NMR spectroscopy. An HPLC system for the discrimination of these benzopyranones has been developed.

A detailed view on the constituents of EPs 7630.

Extracts of PELARGONIUM SIDOIDES, commonly known as EPs 7630, are produced by extraction of milled roots with 11 % (w/w) ethanol in water. This solvent leads to a spectrum of constituents which differs significantly from extracts obtained by extraction with non-polar solvents. EPs 7630 is composed of six main groups of constituents, namely unsubstituted and substituted oligomeric prodelphinidins, monomeric and oligomeric carbohydrates, minerals, peptides, purine derivatives and highly substituted benzopyranones. The oligoprodelphinidins, frequently supposed to be compounds with unspecific tanning interactions, show, in contrast to other polyphenols, an amazing variety of substructures and connectivities which results in an uncommon diversity even at a low degree of polymerization. Three distinct purine derivatives, second messengers and probably intermediates of DNA synthesis, were identified and characterized by phytochemical means. The main benzopyranones of EPs 7630 are highly oxygenated at the phenyl moiety (three to four oxygens) and in addition sulfated at distinct positions. A disulfate of 6,7,8-trihydoxybenzopyranone has been identified for the first time in plants. Taken together, these constituents amount to about 70 to 80 % of the total weight of EPs 7630, the active ingredient of the phytopharmaceutical Umckaloabo (Iso Arzneimittel Ettlingen).

Unpaired spin densities from NMR shifts and magnetic anisotropies of pseudotetrahedral cobalt(II) and nickel(II) vinamidine bis(chelates).

The distribution of unpaired electron spin over all regions of the organic ligands was extracted from the large positive and negative 1H and 13C NMR paramagnetic shifts of the title complexes. Owing to benevolent line broadening and to very high sensitivities of approximately 254,000 and approximately 201,000 ppm/(unpaired electron spin) for Co(II) and Ni(II), respectively, at 298 K in these pseudotetrahedral bis(N,N'-chelates), spin transmission through the sigma- (and orthogonal pi)-bonding system of the ligands could be traced from the chelate ring over five to nine sigma bonds. Most of those "experimental" spin densities DeltarhoN (situated at the observed nuclei) agree reasonably well with quantum chemical DeltarhoDFT (DFT = density functional theory) values and provide an unsurpassed number of benchmark values for the quality of certain types of modern density functionals. The extraction of DeltarhoN became possible through the unequivocal separation of the nuclear Fermi contact shift components from the metal-centered pseudocontact shifts, which are proportional to the anisotropy Deltachi of the magnetic susceptibility: Experimental Deltachi values were obtained in solution from measured deuterium quadrupole splittings in the 2H NMR spectra of two deuterated model complexes and were found to be nonlinear functions of the reciprocal temperature. This provided the reliable basis for predicting metal-centered pseudocontact shifts for any position of a topologically well-defined ligand at varying temperatures. The related ligand-centered pseudocontact shifts were sought by using the criterion of their expected nonlinear dependence on the reciprocal temperature. However, their contributions could not be differentiated from other small effects close to the metal center; otherwise, they appeared to be smaller than the experimental uncertainties. The free activation energy of N-aryl rotation past a vicinal tert-butyl substituent in the Ni(II) vinamidine bis(N,N'-chelates) is DeltaG++(+74 degrees C) approximately 17.0 kcal/mol and past a vicinal methyl group DeltaG++(-6 degrees C) approximately 13.1 kcal/mol.

Coumarin derivatives with tumor-specific cytotoxicity and multidrug resistance reversal activity.

A preliminary exploration of coumarin derivatives as novel multidrug resistance (MDR) modulators was carried out to determine the basic features of the structure responsible for the MDR reversal activity. Among 44 coumarins, 14 compounds moderately induced the reversal of MDR (fluorescence activity ratio (FAR) values > 1). The most active compound, 6-hydroxy-3-(2-hydroxyethyl)-4-methyl- 7-methoxycoumarin [C34], was equally potent as a MDR modulator verapamil. These data show a relationship between the chemical structure and MDR-reversal effect on tumor cells. All coumarins tested were more cytotoxic against tumor cells than normal cells. Several compounds displayed potent cytotoxic activities (CC50 15 - 29 microg/mL in HSC cells), comparable with that of gallic acid (CC50 = 24 microg/mL). Both 6-hydroxy- 7-methoxy-4-methyl-3-isopropylcoumarin [C43] and 3-ethyl-6-hydroxy- 7-methoxy-4-methylcoumarin [C44] showed the highest tumor-specific cytotoxicity (SI value = 4.1 and 3.6, respectively). We conclude that coumarins are potentially potent new MDR modulators with low toxicity against normal cells. A deeper understanding of the relationship between their structures and their potency will contribute to the design of optimal agents.

Structural requirements of hydroxylated coumarins for in vitro anti-Helicobacter pylori activity.

We have previously found that a 7-hydroxycoumarin derivative has potent anti-Helicobacter pylori (H. pylori) activity, comparable with metronidazole. In this report, we describe the structural requirement for the anti-H. pylori activity of several hydroxylated coumarins (1-23). It was found that 7-hydroxy-4-methylcoumarin (6), 6,7-dihydroxy-4-methylcoumarin (8), 6-hydroxy-7-methoxy-4-methylcoumarin (10) and 5,7-dihydroxycyclopentanocoumarin (21) showed comparable anti-H. pylori activity with metronidazole. The presence of 7- and/or 6-hydroxyl groups seems to be essential to display higher anti-H. pylori activity. Their activities depended on the number and position of the hydroxyl group on the benzenoid ring of the coumarin system. Methylation of the hydroxy group generally diminished the activity. In hydroxylated coumarins, the methyl group at C-4 position enhanced the activity. The inhibitory activity of coumarins (1-23) against jack bean urease was examined, but no coumarins showed any inhibition at 160 micrograms/mL.

Structure-cytotoxic activity relationships of simple hydroxylated coumarins.

Several hydroxylated and/or methoxylated coumarin derivatives were tested for their relative cytotoxicity on four human tumor cell lines (oral squamous cell carcinoma HSC-2, HSC-3, melanoma A-375 and promyelocytic HL-60) and three normal human cells (gingival fibroblast HGF, periodontal ligament fibroblast HPLF and pulp cell HPC). Tumor cell-specific cytotoxicity was detected in all 6,7-dihydroxy-substituted coumarins only. The observations indicate that the tumor-specific cytotoxicity of the naturally occurring coumarin esculetin can be further enhanced by proper substitutions at 3- and/or 4-position(s) of the molecule. Agarose gel electrophoresis revealed that esculetin and its derivatives with tumor-specific cytotoxicity induce internucleosomal DNA fragmentation in HL-60 cells.