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PubMed1983

HDL-cholesterol increase in normolipaemic subjects on khellin: a pilot study.

An evaluation has been made of the action of khellin, a furochromone derivative from Ammi visnaga, at the dose of 50 mg q.i.d. during four weeks, on the plasma lipids of 20 non-obese normolipaemic male subjects after a placebo period of two weeks. The plasma lipids were measured each week and one week after discontinuation of treatment; 14 subjects were evaluable. Plasma total cholesterol and triglycerides concentrations remained unchanged throughout the study, whereas HDL-cholesterol levels were significantly increased from the first week until one week post-medication. A lowering of the LDL-C/HDL-C ratio was shown during the same period. No specific effect on plasma LCAT activity was obtained. Compliance, checked by the plasma khellin determination, was good. Some untoward effects were observed. Nausea and vomiting were responsible for the withdrawal of four volunteers, and elevation of SGOT and SGPT for that of two others. It can be concluded that khellin at this dosage induces an important shift of cholesterol to the HDL fraction which is maintained until one week post-medication.

Adult↗

PubMed1978

Spectrophotometric determinations of 3-dimethylaminomethylkhellin hydrochloride and khellin.

Spectrophotometric assays are proposed for the determination of 3-dimethylaminomethylkhellin hydrochloride and khellin in bulk chemical and dosage forms. The acid dye method, using methyl orange at pH5, is applied to assay the amine in the form of an ion-pair extractable in chloroform with maximum abosrbance at 420 nm. The perchloric acid method, depending on formation and extraction of the oxonium salts of both compounds, is used to assay the amine and khellin at 333 or 430 nm and at 325 or 410 nm, respectively. The reineckate method can be used to assay the amine as the reineckate derivative in acetone with maximum absorbance at 530 nm. However, small amounts of the amine (1.5--3 mg) can be determined as the reineckate in methanol with maximum absorbance at 245 nm. Stability determination of the two compounds can be done by the acid dye and perchloric acid methods. The three methods are sufficiently accurate, sensitive, and precise.

Drug Stability↗

PubMed1995

Khellin, but not 8-methoxypsoralen, inhibits adenylyl cyclase system in HeLa cells.

Until recently, the therapeutic effects of furocoumarins and furochromones plus UV-A light were thought to be due to their ability to form photoadducts with DNA in the cell nuclei; now it appears that membrane effector systems may be involved as targets. Here we show that in HeLa cells khellin at 1 and 5 microM final concentration, in combination with UV-A light, inhibits NaF-stimulated adenylyl cyclase activity and Pertussis Toxin (PT)-catalyzed ADP-ribosylation of alpha-subunits of inhibitory guanine nucleotide regulatory proteins (Gi) and increases GTPase activity. In the same experimental conditions, 8-methoxypsoralen (8-MOP), either alone or plus UV-A, does not affect adenylyl cyclase and GTPase activities. Our results suggest that in HeLa cells, through an interaction with a receptor and the mediation of Gi proteins, the adenylyl cyclase system is a target for khellin but not for 8-MOP.

Adenosine Diphosphate Ribose↗

PubMed1993

Determination of khellin in serum by gas chromatography.

A rapid gas chromatographic assay has been developed for the separation and determination of khellin in human serum. Using a DB-17 capillary column and a simple chloroform extraction, khellin and an internal standard, trioxsalen, were separated from endogenous substances without further clean-up. Spiked serum samples in the range 0.11-1.1 micrograms/ml were assayed and a linear calibration curve obtained.

Chromatography, Gas↗

PubMed2006

Ultraviolet photoionization of the photosensitizers khellin and visnagin in aqueous solution and in micelles: one-photon ionization is a minor process.

One-photon ionization, leading to formation of hydrated electrons and radical cations, has been proposed as a possible mechanism of action of some sensitizers in photobiology. In this contribution, we have investigated this proposal for the compounds khellin and visnagin, used in photomedical applications. Nanosecond transient absorption spectroscopy covering a wide range of laser pulse energies was employed to measure the formation of radical cations and hydrated electrons in aqueous solution and in cationic (CTAB) as well as anionic (SDS) micellar solutions. A model allowing for simultaneous one- and two-photon processes and fully accounting for the nonlinearity of the pulse energy dependence was used to simulate the data. The results did not support the hypothesis of a significant role of one-photon ionization, the upper limits of the quantum yields of radical cation formation being phi < 0.01 for visnagin and phi < 0.004 for khellin.

Free Radicals↗

PubMed1990

[The effect of khellin and timefurone on secretion and catabolism of lipoproteins by cultured human and rabbit hepatocytes].

Using human and rabbit hepatocyte cultures, the effects of khellin and timefurone on lipoprotein metabolism were studied with special reference to the following parameters: i) binding and degradation of 125I-labeled low density lipoproteins (LDL); ii) apoprotein B (apo-B) secretion measured by immunoenzymatic assay, iii) [35S]methionine labeled apo-B and apo-E within the composition of very low density lipoproteins (VLDL); iiii) total cholesterol synthesis and cholesterol secretion within the composition of VLDL. The therapeutic concentrations (0.1-10 micrograms/ml) of the above drugs had no appreciable effect on the binding and degradation of 125I-LDL but inhibited the secretion of apo-B VLDL, leaving the apo-E VLDL unaffected. This was paralleled with inhibition of cholesterol synthesis (by 30-50%) and VLDL secretion. These results suggest that khellin and timefurone mediate the hypolipidemic effect via the reduction of the intracellular synthesis of cholesterol and secretion of apo-B containing VLDL by hepatocytes.

Animals↗

PubMedDate not supplied

High performance liquid chromatography analysis of the furanochromones khellin and visnagin in various organs of Ammi visnaga (L.) Lam. at different developmental stages.

The content of the furanochromones khellin and visnagin, in the organs of Ammi visnaga (L.) Lam. at different developmental stages, has been examined. Determinations have been performed by means of a high performance liquid chromatography (HPLC) technique which allows both the separation and the quantitative determination of these chromones. Unripe fruits are the richest in both chromones, but the collection of ripe dry fruits--as it occurs in Egyptian folk-medicine--seems more reasonable because they might not undergo degradation processes during desiccation and storage.

Chromatography, High Pressure Liquid↗

PubMed1997

Studies on the photobiological activity of two naturally occurring furochromones, visnagin and khellin, in Chlamydomonas reinhardtii.

Irradiation of arg-1 cells of the green alga Chlamydomonas reinhardtii with UV-A in the presence of visnagin (10 microg/ml) produced weak mutagenic effects when a fluence rate of 5.1 W/m2 and fluences of 1.5-36.7 kJ/m2 were applied. A maximum number of revertants was obtained at approximately 9.2 kJ/m2. When a fluence rate of 20.4 W/m2 was used the photomutagenicity of visnagin was markedly enhanced with fluences of > or = 36.7 kJ/m2. In survival experiments with a fluence rate of 5.1 W/m2 the surviving fraction decreased continuously to approximately 4%. In experiments with a fluence rate of 20.4 W/m2, however, higher survival rates were observed compared at equal UV-A doses. Visnagin was much less phototoxic and photomutagenic than bergapten when compared at equimolar concentrations and equal UV-A doses. Re-irradiation with UV-A in the absence of unbound visnagin did not alter survival and mutagenicity which had been induced by the first treatment. The mutation frequency plotted versus the UV-A fluence exhibited second-order kinetics. Khellin showed only marginal photosensitizing capacity and no significant mutagenicity up to a concentration of 100 microg/ml and a total UV-A fluence of 73.4 kJ/m2.

5-Methoxypsoralen↗

PubMed2004

Treatment of vitiligo with local khellin and UVA: comparison with systemic PUVA.

Vitiligo is an idiopathic leukoderma often with a progressive course causing destruction of melanocytes. The best methods for achieving cosmetically acceptable re-pigmentation of affected skin appear to be both local and systemic PUVA. They may, however, cause serious side effects, which is an argument for conducting research into new, equally effective photo-chemotherapeutic agents. One of these agents is khellin. We conducted a pilot study in 33 patients to evaluate the effectiveness of local KUVA and systemic PUVA therapy for vitiligo and to compare them in terms of the degree of re-pigmentation, duration of treatment, number of procedures, total UVA dose and side effects. Local KUVA required longer duration of treatment and higher UVA doses. KUVA-induced re-pigmentation depended on the age of the patients (r = -0.61, P = 0.001), and better results were achieved with younger individuals [% re-pigmentation = 81.76 - (1.48 x age in years)]. No side effects were observed in cases of local KUVA treatment. Erythema, itching and gastro-intestinal disturbances occurred with some patients treated with PUVA. The results demonstrate that local KUVA may effectively induce re-pigmentation of vitiligo-affected skin areas to a degree comparable to that achieved when using systemic PUVA, provided that treatment duration is long enough.

Adolescent↗

PubMed1998

Photophysical properties and photobiological activity of the furanochromones visnagin and khellin.

The larger photobiological activity of visnagin (VI) versus khellin (KH) toward several living organisms, including fungi, viruses, yeasts and bacteria, induced a detailed investigation of the photophysical properties of these naturally occurring furanochromones, using laser-flash-photolysis, photoacoustic calorimetry and fluorescence (steady-state and time-resolved) techniques in solvents with different polarity and content of water, including micelles and vesicles. The results have shown that the magnitude of all the three rate constants out of S1 (radiative, kf; internal conversion, kic and intersystem crossing, kisc) for VI and KH strongly depend on the solvent, namely on its hydrogen bonding ability and polarity. The changes of kf and kisc are due to the solvent-assisted mixing and/or inversion of the two first singlet excited states (1n, pi and 1 pi, pi), while kic increases with a decrease of the S0-S1 energy gap. As a consequence, the quantum yield of triplet formation (phi T) strongly decreases from values of approximately 0.8 in dioxane to < 0.05 in water for both compounds. The magnitude of solvent polarity/hydrogen bonding ability required, at which the state order is inverted and phi T starts to decrease, is greater for VI than for KH and consequently phi T (VI) >> phi T (KH) over a broad range of water content including that appropriate to the environment of the compounds in a living system. These facts account for the larger photobiological activity of VI with respect to KH, regarding both the fungus Fusarium culmorum L. and the wild strain of Escherichia coli, studied by us.

Chemical Phenomena↗

PubMedDate not supplied

Long-term results in the treatment of vitiligo with oral khellin plus UVA.

This study was performed to assess the effectiveness and short-term and long-term safety of oral khellin plus UVA (KUVA) in patients with vitiligo. Twenty-eight patients (13 males and 15 females; mean age, 34 years; [age range, 15-51 years]) most with extensive generalized vitiligo of more than 6 months duration had received KUVA at sometime during a 14-year period. The response to treatment (i.e. repigmentation of depigmented areas) was rated retrospectively comparing photographs taken before and after therapy and correlation analysis revealed that it was statistically significantly linked to the number of KUVA treatments (r = 0.833, P = 0.001) and to total cumulative UVA dose (r = 0.840, P = 0.001). Of 17 patients who had continued therapy for longer than 3 months, 7 (41%) had a good response (i.e., more than 70% repigmentation of lesional skin) after a mean of 194 treatments (range, 69-386 treatments) and a mean cumulative UVA dose of 2,036 J/cm2 (range, 690-4,411 J/cm2), whereas lower response grades were observed in the patients with lower treatment numbers. The most common short-term side effect was mild nausea, occurring in 8 of 28 patients (29%), and mainly in the first week(s) of treatment. Follow-up assessment at a mean of 40 months (range, 4-110 months) after the end of KUVA therapy available in 23 of 28 patients revealed no skin cancers or actinic skin damage in any patient. These data indicate that KUVA seems to be safe as well as effective for vitiligo, provided treatment is administered long enough.

Adolescent↗

PubMed2002

From khellin to sodium cromoglycate--a tribute to the work of Dr. R. E. C. Altounyan (1922-1987).

Sodium cromoglycate, which was launched in 1968 by the British company Fisons for the treatment of allergies and asthma, was an absolute novelty in chemical, pharmacological as well as therapeutic respects. The khellin derivative meanwhile did not owe its discovery to the usual strategies for finding drugs. On the contrary, the protective effect of the substance was discovered in a self trial through systematic antigen-induced provocation tests of the medicinal doctor and allergic Roger Ernest Collingwood Altounyan (1922-1987). The only subsequently formed hypothesis of a mast cell stabilising effect of Sodium cromoglcycate did not prove to be valid for the search for similar or more effective substances. A further development of this drug class could not take place because of the lack of suitable pharmacological models.

Anti-Asthmatic Agents↗

PubMed1952