Antifungal activity of microbial secondary metabolites.

Secondary metabolites are well known for their ability to impede other microorganisms. Reanalysis of a screen of natural products using the Caenorhabditis elegans-Candida albicans infection model identified twelve microbial secondary metabolites capable of conferring an increase in survival to infected nematodes. In this screen, the two compound treatments conferring the highest survival rates were members of the epipolythiodioxopiperazine (ETP) family of fungal secondary metabolites, acetylgliotoxin and a derivative of hyalodendrin. The abundance of fungal secondary metabolites indentified in this screen prompted further studies investigating the interaction between opportunistic pathogenic fungi and Aspergillus fumigatus, because of the ability of the fungus to produce a plethora of secondary metabolites, including the well studied ETP gliotoxin. We found that cell-free supernatant of A. fumigatus was able to inhibit the growth of Candida albicans through the production of a secreted product. Comparative studies between a wild-type and an A. fumigatus ΔgliP strain unable to synthesize gliotoxin demonstrate that this secondary metabolite is the major factor responsible for the inhibition. Although toxic to organisms, gliotoxin conferred an increase in survival to C. albicans-infected C. elegans in a dose dependent manner. As A. fumigatus produces gliotoxin in vivo, we propose that in addition to being a virulence factor, gliotoxin may also provide an advantage to A. fumigatus when infecting a host that harbors other opportunistic fungi.

Characterisation of the binding of digitoxin and acetyldigitoxin to human serum albumin by high-performance affinity chromatography.

Zonal elution and high-performance affinity chromatography were used to examine interactions of the drugs digitoxin and acetyldigitoxin with the protein human serum albumin (HSA). This was done by injecting small amounts of digitoxin and acetyldigitoxin onto an immobilized HSA column in the presence of mobile phases that contained various concentrations of digitoxin, acetyldigitoxin or other solutes as competing agents. A fixed concentration of beta-cyclodextrin was also present in the mobile phase as a solubilising agent. It was found that digitoxin and acetyldigitoxin each had strong interactions at a single common binding site on HSA, but with slightly different equilibrium constants for this region. Neither compound showed any competition with warfarin or L-tryptophan, which were used as probes for binding at the warfarin-azapropazone and indole-benzodiazepine sites of HSA. These results confirmed the presence of a separate binding region on HSA for digitoxin-related compounds.

Separation of cardiac glycosides by micellar electrokinetic chromatography and microemulsion electrokinetic chromatography.

The interest of micellar electrokinetic chromatography (MEKC) and microemulsion electrokinetic chromatography (MEEKC) for the resolution of four cardiac glycosides is demonstrated. First, the influence of some parameters on the resolution of the solutes in MEKC such as the concentration of the surfactant, pH, addition of organic modifiers and urea is discussed. Then, results are compared with those obtained in MEEKC using different microemulsion compositions. Results indicate that MEEKC possesses several advantages over MEKC for the separation of relatively hydrophobic compounds such as digitalic compounds. First, microemulsions allow a better manipulation of the migration time window and of the retention of the solutes. Moreover, efficiency is improved with shorter analysis time.

High-performance liquid chromatography-ionspray mass spectrometry for the specific determination of digoxin and some related cardiac glycosides in human plasma.

An original method based upon high-performance liquid chromatography coupled to ionspray mass spectrometry (HPLC-ISP-MS) has been developed for the identification and quantification in plasma of several cardiac glycosides, namely digoxin, digitoxin, lanatoside C and acetyldigitoxin. After single-step liquid-liquid extraction by chloroform-2-propanol (95:5, v/v) at pH 9.5 using oleandrin as an internal standard, solutes are separated on a 4 microm NovaPak C18 (Waters) column (150x2.0 mm, I.D.), using a gradient of acetonitrile-2 mM NH4COOH, pH 3 buffer (flow-rate 200 microl/min, post-column split 1:3). Detection is done by a Perkin-Elmer Sciex API-100 mass analyzer equipped with an ISP interface. In most instances the major ion observed is not [M+H]+ as expected, but [M+NH4]+. The mean retention times (min) are: lanatoside C, 5.74; digoxin, 6.00; digitoxin, 8.08, oleandrin, 8.30, acetyldigitoxin, 8.66 and 9.01 (isomers alpha and beta, respectively). The lower limits of detection in single ion monitoring mode range from 0.15 ng/ml (alpha- and beta-acetyldigitoxin) to 0.60 ng/ml (lanatoside C), making the method less sensitive than radioimmunoassay, whereas it is much more specific.

[Guidelines for prescription of the assay of digitalis glycosides by immunologic methods]. / Règles de prescription du dosage des digitaliques par méthodes immunologiques.

Digoxin, digitoxin and acetyldigitoxin are the most widely prescribed of cardiotonic glycosides. Analytical exploration can be performed by a single assay when only one compound is prescribed or by multiple assays in cases of imprecise prescription or when several glycosides are given concomitantly. In addition, the metabolic transformation of digitoxin into digoxin and the presence of endogenous "digitalis-like compounds" mean that a number of precautions must be taken during prescription. These examples underline the ambiguity of the so-called "digitalinaemia" prescriptions and the need for biologists to be supplied with maximum information by clinicians.

Effects of digoxin and acetyl-digitoxin on basal and CO2-stimulated ventilation.

Eight healthy volunteers were studied to ascertain the effect of digoxin and the relatively more lipophylic cardiac glycoside, acetyl-digitoxin on ventilation. Baseline ventilation as well as the response to the inspiration of 2.2% and 4.8% carbon dioxide were assessed. Digoxin produced a depression of minute volume and oxygen consumption whereas acetyl-digitoxin produced the opposite effect. This could be the result of a relatively greater vagomimetic effect with digoxin and a greater symphatomimetic effect with acetyl-digitoxin. These findings might have clinical implications in cardiac patients who have pulmonary disease.

Adverse drug reactions (ADRs) in patients with heart diseases. Comparison between patients without and with heart failure.

Adverse drug reactions (ADRs) may be more frequent in patients who present some diseases. By means of an intensive prospective drug surveillance work, 492 patients with heart diseases, hospitalized at the Department of Medicine of the Clinical Hospital of the University of Chile, were studied in order to determine the frequency and characteristics of ADRs. ADRs were significantly more frequent in patients with heart failure (HF) (30.0%) than in those without HF (22.7%)(p less than 0.05). Patients presenting HF developed more metabolic disturbances than patients not presenting HF (p less than 0.001). Furosemide was the most frequently used drug in both groups, but treatment with it was longer in patients with HF who presented a significantly higher frequency of adverse reactions to this diuretic (p less than 0.05). 89.9% of ADRs in patients without HF and 93.8% of ADRs in those with HF, were dose-related effects. Analyses of some predisposing factors to ADRs, such as age, number of drugs administered, duration of hospitalization, ADR or allergy histories and presence of a renal failure, did not explain differences found between ADRs in patients without and with HF. These findings suggest that heart failure may be a determinant of frequency and characteristics of ADRs.

[Pharmacokinetics and cardiac effect of beta-acetyldigoxin and digitoxin in combination therapy with nifedipine]. / Pharmakokinetik und kardiale Wirksamkeit von beta-Acetyldigoxin und Digitoxin unter einer Kombinationstherapie mit Nifedipin.

The effect of nifedipine (N) on the pharmacokinetics and pharmacodynamics of beta-acetyldigoxin (AD; n = 11) and digitoxin (DGT; n = 10) was studied in 21 patients with cardiac insufficiency stage II-III NYHA. Glycoside plasma concentration and renal excretion as well as electrocardiogram heart rate, atrioventricular transconduction time (PQ), duration of electrical systole corrected for heart rate (QTc), mean amplitude of T waves in leads V2 to V6 (TV2-6) and systolic time intervals total electromechanical systole index (QS21), left ventricular ejection time index (LVETI), pre-ejection period index (PEPI), PEP/LVET-ratio were recorded repeatedly before and during co-administrations of 40-60 mg/day N. Plasma AD concentrations were 0.64 +/- 0.22 ng/ml (mean +/- SD) before and 0.61 +/- 0.21 ng/ml during co-administration of N over 10-14 days, plasma DGT concentrations 13.9 +/- 4.1 ng/ml before and 13.7 +/- 4.5 ng/ml during co-administration of N over 4-6 weeks. Daily glycoside excretion was not affected by treatment with N. Heart rate and PQ-interval were not significantly changed during co-administration of N whereas T-wave flattening was intensified and QT-duration was lengthened. Concomitant treatment of AD and N led to an increase of PEPI and PEP/LVET compared to AD alone in ten patients whereas the systolic time intervals after concomitant treatment of DGT and N in most patients did not differ from those after DGT alone. From our findings we conclude that N had no clinically significant effect on pharmacokinetics and pharmacodynamics of AD or DGT.

[Acute fatal non-occlusive intestinal ischemia during treatment with a cardiotonic glucoside]. / Ischémie intestinale aiguë non occlusive mortelle au cours d'un traitement par glucoside cardiotonique.

After presenting the case of a 70 year old woman who presented a massive mesenteric infarction as a result of non-occlusive intestinal ischaemia ( NOII ), the authors review the principal features of this particular form of intestinal ischaemia. This condition is seen principally in elderly people with a syndrome of low cardiac output, resulting in marked mesenteric vasoconstriction. It is a complication of either severe decompensated heart disease treated with digitaloids or to a state of hypovolaemic or septic shock. The diagnosis of NOII should be suggested by the combination of abdominal signs with a state of shock and/or treated heart disease. The diagnosis is confirmed by selective mesenteric arteriography which reveals a patent but spastic vessel. The treatment is initially medical, consisting of the correction of haemodynamic disturbances and the in situ injection of vasodilator products, which may need to be completed by a surgical operation. However, the prognosis of NOII remains serious, particularly because of the frequent delay in making the diagnosis.

[Pharmacological properties of adicin, Soviet alpha-acetyldigitoxin]. / Farmakologicheskie svoistva aditsina--otechestvennogo al'fa-atsetildigitoksina.

Adicin, Soviet alpha-acetyldigitoxin, obtained from Digitalis lanata Ehrh., c. Scrophulariaceae after isolation from it of celanid is a highly effective cardiotonic of the digitalis type of action. It exerts a favourable ino- and tonotropic and an adverse chronotropic action on the heart. This action is brought up in varied animal species and can be observed for a long time (over 3 hours). Adicin produces no adverse effect on the coronary blood flow and it is conducive to the improvement of venous circulation. The drug does not differ considerably from acedoxin (Hungarian alpha-acetyldigitoxin) from the standpoint of the cardiotonic effect, cumulative properties, elimination rate, biological activity and toxicity. Adicin is recommended for clinical trials with a purpose of replacing imported drugs.

Measurement of plasma glycoside level following pengitoxin administration.

16-Acetyl-gitoxin, the cardioactive metabolite of pengitoxin, was estimated by the 86Rb uptake technique. In 70 consecutive patients taking an oral maintenance dose of pengitoxin 0.4 mg (Pentagit), the mean plasma concentration was 20.8 +/- 6.7 ng/ml. Toxic signs were not observed up to plasma levels of 40 ng per ml.

Pharmacokinetic investigations in man of two acetyl derivatives of 16alpha-gitoxin.

3H-16-acetyl-16alpha-gitoxin or 3H-penta-acetyl-16alpha-gitoxin were injected iv or administered po to 15 volunteers and 3 patients. The elimination half-life and excretion in urine within 4 days were estimated as a percentage of the administered radioactivity, and metabolic studies on the fate of the administered glycosides were performed. In volunteers the following results were obtained: 3H-16-acetyl-16alpha-gitoxin 1 mg iv.: 50 +/- 11 h, 28.3 +/- 4.1%; 3H-16-acetyl-16alpha-gitoxin 1mg po: 48 +/- 8 h, 25.4 +/- 2.8%; 3H-penta-acetyl-16alpha-gitoxin 2 mg po: 51 +/- 12 h, 20.7 +/- 3.2%, respectively. In 3 patients with a cannulated bile duct 9.9% (mean) of the administered 3H-16-acetyl-16alpha-gitoxin was excreted. By comparison of the radioactivity excreted in urine following the 2 routes of 16-acetate administration, the percentage absorption was calculated to be 88.5%. In serum and urine 16-acetyl-16alpha-gitoxin and 16alpha-gitoxin were found as possible metabolites of both glycosides, in the ratio of 75-85:15-25, and both metabolites were also found in bile. Within 16 h after penta-acetate administration, two additional metabolites (bis-acetyl-derivatives of 16alpha-gitoxin) were detected in serum and urine within 16 h after administration of penta-acetate.