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PubMed1998

Inhibition of metabolic activation of the promutagens, benzo[a]pyrene, 2-aminofluorene and 2-aminoanthracene by furanochromones in Salmonella typhimurium.

Khellin, a naturally occurring furanochromone (Ammi visnaga fruits), inhibited the mutagenicity of the promutagens benzo[a]pyrene, 2-aminofluorene and 2-aminoanthracene in Salmonella typhimurium TA98. The effect varied greatly and depended on the S9 fraction used. Cytosolic activation of 2-aminoanthracene was also inhibited. Khellin produced no effect or only weak activity against the direct acting mutagens 2-nitrofluorene, 4-nitro-o-phenylenediamine, 1-nitropyrene and ethylmethane sulfonate (in TA100). Daunomycin mutagenicity was inhibited to a greater extent. Visnagin was more toxic, but showed similar effects. Khellol and its glucoside were inactive against all the mutagens tested. We conclude that khellin acts as an inhibitor or the microsomal cytochrome P450 sub-enzymes analogous to the related furanocoumarins and is also capable of inhibiting cytosolic enzymes. The extract from Ammi visnaga fruits showed a higher inhibition potency than khellin alone against 2-aminoanthracene, 1-nitropyrene and daunomycin. This might be due to additional inhibitors, e.g. coumarins, or to the synergistic effects of accompanying compounds.

Animals↗
PubMedDate not supplied

Effect of benzopyrone derivatives on drug activity and metabolism.

In female rats, zoxazolamine paralysis time and mortality caused by indomethacin were significantly reduced by pretreatment with khellin, 7,8-benzoflavone or rutin. Pretreatment with khellin and 7,8-benzoflavone increased the in vitro zoxazolamine and ethylmorphine metabolism. These results were compared with those obtained by equimolar doses of phenobarbital, pregnenolone-16 alpha-carbonitrile and spironolactone in experiments performed simultaneously. It was concluded: Khellin, 7,8-benzoflavone and rutin increased the body's resistance to drugs via induction of the drug metabolizing enzymes of the liver, this action has about the same magnitude with that of phenobarbital and pregnenolone-16 alpha-carbonitrile. For the benzopyrone derivatives, some common structural features have been indicated as probable structural requirements for drug metabolizing enzyme inductive activity in this group of compounds.

Animals↗
PubMed1990

Solvent spin-labelling for investigating the interaction of biological ligands with macromolecules. A 1H paramagnetic relaxation study.

The paramagnetic contributions to the spin-lattice relaxation rates of khellin protons, induced by the presence in an aqueous solution of TEMPO nitroxide, have been analyzed in the interaction of the furochromone with DNA. The relaxation data obtained at different temperatures, nitroxide and DNA concentrations indicate that the average solvent exposure of the furanic moiety of khellin is lower than that of the pyranic group. This feature suggests that the former is the main site of approach of khellin to DNA.

DNA↗
PubMed1995

Provocation of porphyria cutanea tarda by KUVA-therapy of vitiligo.

Therapy with khellin and UVA irradiation (KUVA) is a therapeutic approach to vitiligo. Little is known about the photobiological properties of khellin and its long-term side-effects after prolonged administration. A 47-year-old woman suffering from acral vitiligo since the age of 3 is reported, who developed blisters on hands and fingers during KUVA-therapy. Laboratory findings were consistent with hereditary porphyria cutanea tarda. Electron microscopic examination of a blister revealed clefting below the basement membrane. It is proposed that khellin in some way provoked the porphyria cutanea tarda in this patient.

Basement Membrane↗
PubMedDate not supplied

Inhibition of cAMP phosphodiesterase by some phototherapeutic agents.

The behaviour of cyclic-3',5'-AMP phosphodiesterase has been studied in the presence of psoralen, 8-methoxy-psoralen (8-MOP), 4,5',8-trimethylpsoralen (TMP) (usually used in PUVA therapy), 4,6,4'-trimethylangelicin (TMA) and khellin recently proposed for the same therapeutical use. TMP and TMA exhibit a significant inhibitory effect on cyclic AMP phosphodiesterase; a light inhibition is produced by khellin at rather high concentration.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1976

On the solubilization properties of surfactant-polymer complexes.

Polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP) affect the solubilization properties of sodium dodecyl sulphate (SDS). When these polymers are added to SDS solution, its solubilization power for riboflavin, khellin and propyl p-hydroxybenzoate is markedly decreased. In case of riboflavin and khellin, the polymer effect is more pronounced at high surfactant concentrations; for propyl p-hydroxybenzoate, the polymer effect is inversely proportional to the surfactant concentration. On the other hand, the solubilization power of SDS towards methyl and butyl p-hydroxybenzoate is greatly enhanced by PEG or PVP. In case of methyl p-hydroxybenzoate the effect of PEG is more pronounced at high surfactant concentrations; the effect of PVP is not significantly dependent on the surfactant concentration. For butyl p-hydroxybenzoate, the polymer effect decreases markedly with increasing surfactant concentration.

Khellin↗
PubMedDate not supplied

Photosynthesis of furocoumarin- and furochromone-types potential intercalative alkylating and oxidizing agents of DNA through photooxidations using gamma-ray.

The photooxygenation of imperatorin (1a) under gamma-ray irradiation afforded the hydroperoxides 2a and 3a. Similarly, the photooxygenation of alloimperatorin (1b) gave the hydroperoxide (2b). Visnagin (1c) was also photooxygenated to give the hydroperoxide (2c) as sole product. On the other hand, the photooxygenation of khellin (1d) gave the endoperoxide (2d) as a sole product. The epoxidation of imperatorin (1a) using hydrogen peroxide under gamma-ray irradiation afforded the epoxide 5a. Similarly visnagin (1c) and khellin (1d) were epoxidized to give the epoxides 5c and 5d.

Alkylating Agents↗
PubMed2003

Effect of psoralens on Fenton-like reaction generating reactive oxygen species.

Psoralens (psoralen, 5-methoxypsoralen, 8-methoxypsoralen, khellin, and visnagin) in 1 mM doses were shown to enhance the generation of reactive oxygen species, such as the hydroxyl radical (HO*), the superoxide anion radical (O2(-)), and singlet oxygen ((1)O(2)), from the system generating chemiluminescence (CL), as well as free radicals in the absence of light. The system that generated CL was made up of CoCl(2) and H(2)O(2). Incubation of psoralens in 0.2 mM doses with the generating system showed that only 8-methoxypsoralen and khellin have antioxidative effects. Antioxidative effects were also observed in the case of visnagin but in low concentration (0.05 mM). High doses of psoralens (1 mM) showed prooxidative effects. Measurements were done using a deoxyribose assay, the CL method, and spin-trapping with 5,5-dimethyl-1-pyrroline-N-oxide and 2,2,6,6-tetramethylpiperidine combined with electron spin resonance spectroscopy and spectrophotometry methods.

Electron Spin Resonance Spectroscopy↗
PubMed1994

The involvement of a Ca2+ channel blocking mode of action in the pharmacology of Ammi visnaga fruits.

Based on a screening program of medicinal plants for their possible calcium antagonistic mode of action, the most active lipophilic extract of Ammi visnaga fruits (DAB 10) was fractionated by CC and investigated pharmacologically at K+ (60 mM)-depolarized guinea-pig aortic strips. Visnadin, khellin, and visnagin were identified and determined as the effective principles in this testing model with the dihydropyranocoumarin visnadin being the most active. Further selectivity tests against norepinephrine (100 microM)-induced contractions evaluated a possible pharmacological differentiation between these compounds as the furanochromones khellin and visnagin inhibited both spasms to a similar extent while visnadin's activity was significantly higher against K(+)-spasms, suggesting an involvement of a calcium channel blocking mode of action for visnadin.

Animals↗
PubMed2002

A new synthesis of oxadiazole, thiazolidinone, N-phthalimidoamino carbonyl and arylidene derivatives with potential antimicrobial activity.

Condensation of carbohydrazide derivatives Ia, b with dimethyl acetylenedicarboxylate and acetylenedicarboxylic acid yielded benzofuran derivatives II a-d. Reaction of Ib with aromatic aldehydes formed products III a-d. Treatment of compounds III a-d with mercaptoacetic acid yielded the cyclocondensation products (IVa-d). Phthalic anhydride reacted with compounds (Ia, b)to form products (Va, b). It has been found that both khellin and visnagin (VIa, b)react with aromatic aldehydes to give arylidene derivatives (VIIa-e). Condensation of diphenyl nitrilamine with 2-arylidene furochromones VII derivatives afforded cyclo-adducts (VIII a-i). The antibacterial activities of the selected compounds were tested against Staphylococcus aureus, B. subtilis, E. coli, Pseudomonas, Salmonella and Erwinia with good results.

Anti-Bacterial Agents↗