Synthesis of Photoactivatable Acyclic Analogues of the Lobatamides

[structure: see text] The lobatamides and related salicylate enamide natural products are potent mammalian V-ATPase inhibitors. To probe details of binding of the lobatamides to mammalian V-ATPase, three photoactivatable analogues bearing benzophenone photoaffinity labels have been prepared. The analogues were designed on the basis of a simplified acyclic analogue 2. Late-stage installation of the enamide side chain and tandem deallylation/amidation were employed in synthetic routes to these derivatives. Simplified analogue 2 showed strong inhibition against bovine clathrin-coated vesicle V-ATPase (10 nM). Analogues 3-5 were also evaluated for inhibition of bovine V-ATPase in order to select a suitable candidate for future photoaffinity labeling studies.

[Simultaneous determination of aspirin and salicyclic acid by synchronous fluorescence spectrometry]

A simple, rapid and inexpensive fluorimetric method for simultaneously determining ASA and SA in a single scan of the co-existing specimen had been established. When the wavelength interval (delta lambda) is 80 nm for scaning, the amounts of ASA and AS could be quantitatively determined respectively. The fluorescence intensity was linearly related to the aspirin concentration in the range of 4.0 x 10(-6)-1.0 x 10(-4) mol x L(-1) with correlation coefficient 0.9949; the fluorescence intensity was linearly related to the salicyclic acid concentration in the range of 8.0 x 10(-7)-1.0 x 10(-4) mol x L(-1) with correlation coefficient 0.9975, the determination limit was 4.0 x 10(-7) mol x L(-1). The method is simple, rapid and inexpensive, it can be used for medicament analysis.

Exposure of lima bean leaves to volatiles from herbivore-induced conspecific plants results in emission of carnivore attractants: active or passive process?

There is increasing evidence that volatiles emitted by herbivore-damaged plants can cause responses in downwind undamaged neighboring plants, such as the attraction of carnivorous enemies of herbivores. One of the open questions is whether this involves an active (production of volatiles) or passive (adsorption of volatiles) response of the uninfested downwind plant. This issue is addressed in the present study. Uninfested lima bean leaves that were exposed to volatiles from conspecific leaves infested with the spider mite Tetranychus urticae, emitted very similar blends of volatiles to those emitted from infested leaves themselves. Treating leaves with a protein-synthesis inhibitor prior to infesting them with spider mites completely suppressed the production of herbivore-induced volatiles in the infested leaves. Conversely, inhibitor treatment to uninfested leaves prior to exposure to volatiles from infested leaves did not affect the emission of volatiles from the exposed, uninfested leaves. This evidence supports the hypothesis that response of the exposed downwind plant is passive. T. urticae-infested leaves that had been previously exposed to volatiles from infested leaves emitted more herbivore-induced volatiles than T. urticae-infested leaves previously exposed to volatiles from uninfested leaves. The former leaves were also more attractive to the predatory mite, Phytoseiulus persimilis, than the latter. This shows that previous exposure of plants to volatiles from herbivore-infested neighbors results in a stronger response of plants in terms of predator attraction when herbivores damage the plant. This supports the hypothesis that the downwind uninfested plant is actively involved. Both adsorption and production of volatiles can mediate the attraction of carnivorous mites to plants that have been exposed to volatiles from infested neighbors.

6-Alkylsalicylic Acids and 6-Alkylresorcylic Acids from Ants in the Genus Crematogaster from Brunei

The defensive chemistry of two species of ants from Brunei in the genus Crematogaster (Physocrema group) has been investigated. Ants in this group release a white secretion from hypertrophied metapleural glands on their thorax when they are disturbed. Previously, one species in this group has been shown to produce alkylphenols and alkylresorcinols. In the present investigation, similar compounds along with salicylic acids and resorcylic acids that are anacardic acid and olivetolic acid homologs, respectively, are described from two species. The structures of these compounds were suggested by their spectroscopic data and confirmed by direct comparison with synthetic samples. Some of these compounds occur in lichens and have well documented physiological activities.

Improved detection of low vapor pressure compounds in air by serial combination of single-sided membrane introduction with fiber introduction mass spectrometry (SS-MIMS-FIMS)

The use of two methods in tandem, single-sided membrane introduction mass spectrometry (SS-MIMS) and fiber introduction mass spectrometry (FIMS), is presented as a technique for field analysis. The combined SS-MIMS-FIMS technique was employed in both a modified commercial mass spectrometer and a miniature mass spectrometer for the selective preconcentration of the explosive simulant o-nitrotoluene (ONT) and the chemical warfare agent simulant, methyl salicylate (MeS), in air. A home-built FIMS inlet was fabricated to allow introduction of the solid-phase microextraction (SPME) fiber into the mass spectrometer chamber and subsequent desorption of the trapped compounds using resistive heating. The SS-MIMS preconcentration system was also home-built from commercial vacuum parts. Optimization experiments were done separately for each preconcentration system to achieve the best extraction conditions prior to use of the two techniques in combination. Improved limits of detection, in the low ppb range, were observed for the combination compared to FIMS alone, using several SS-MIMS preconcentration cycles. The SS-MIMS-FIMS response for both instruments was found to be linear over the range 50 to 800 ppb. Other parameters studied were absorption time profiles, effects of sample flow rate, desorption temperature, fiber background, memory effects, and membrane fatigue. This simple, sensitive, accurate, robust, selective, and rapid sample preconcentration and introduction technique shows promise for field analysis of low vapor pressure compounds, where analyte concentrations will be extremely low and the compounds are difficult to extract from a matrix like air.

Potentiometric Membrane Electrode for Salicylate Based on an Organotin Complex with a Salicylal Schiff Base of Amino Acid

A novel salicylate-selective electrode based on an organotin complex with a salicylal Schiff base of amino acid salicylaldehydeaminoacid-di-n-butyl-Sn(IV) [Sn(IV)-SAADB] as ionophore is described, which exhibits high selectivity for salicylate over many other common anions with an anti-Hofmeister selectivity sequence: Sal- >> PhCOO- > SCN- > Cl04- > I- > NO3- > NO2- > Br- > Cl- > CH3COO-. The electrode, based on Sn(IV)-SAADB, with a 30.44 wt% PVC, a 65.45 wt% plasticizer (dioctyl phthalate, DOP), a 3.81 wt% ionophore and a 0.3 wt% anionic additive is linear in 6.0 x 10(-6) - 1.0 x 10(-1) mol l(-1) with a detection limit of 2.0 x 10(-6) mol l(-1) and a slope of 62.0 +/- 1.2 mV/decade of salicylate concentration in a phosphate buffer solution of pH 5.5 at 25 degrees C. The influence on the electrode performances by lipophilic charged additives was studied, and the possible response mechanism was investigated by UV spectra. The electrode was applied to medicine analysis and the result obtained has been satisfactory.

Detection of fortification of ginkgo products using nanoelectrospray ionization mass spectrometry

We report here a negative ionization nanoelectrospray ionization mass spectrometry (nanoESI-MS) technique that simultaneously detects active components, terpenes and intact flavonol glycosides, and toxic ginkgolic acids in ginkgo products. Unlike the conventional methods that hydrolyze flavonol glycosides to flavonoids for analysis, this technique directly detects intact flavonol glycosides, enabling differentiation of these natural glycosides from the synthetic flavonoids. Thus, it allows the detection of fortification of ginkgo products, alleviating a common problem encountered by the conventional methods. Analysis of 14 commercial ginkgo products using this technique demonstrates large variations and deviation from the well-accepted standardized ginkgo extract. Four products showed evidence of fortification with synthetic surrogates. Two products were found to have toxic ginkgolic acids that exceed the 5 microg g(-1) limit by as much as 60000 fold. These results emphasize the importance of appropriate monitoring of ginkgo product quality.

[Studies on the quality standard of "Lü Kang Yin Xing Ye Pian"]

OBJECTIVE

The quality control method of "Lü Kang Yin Xing Ye Pian" (LKYXYP) was studied and established.

METHOD

The ginkgolides in LKYXYP were identified by TLC. The compounds of fatty acids in Perillae oil were determined by CC/MS. Flavones, ginkgolides and ginkgolic acids were determined by HPLC.

RESULT

There were good linears relationship between the peak area and concentration, r = 0.999, RSD = 1.2% - 2.5% (n = 5), and recoveries of each composition was above 95%, the contation was stable in 24h.

CONCLUSION

This method is proved to be accurate and able to be applied for the quality control of this preparation.

FT-IR and NMR spectroscopic studies of salicylic acid derivatives. I. Gentisamide -- a metabolite of salicylamide

Gentisamide (GAM, 2,5-dihydroxybenzamide), a minor first-pass metabolite of salicylamide (SAM, 2-hydroxybenzamide), was studied using FT-IR, 1D and 2D homo- and heteronuclear 1H and 13C NMR spectroscopy. GAM was isolated from human urine eight hours after oral administration of SAM. FT-IR, 1H and 13C NMR spectra unequivocally confirmed the chemical structure of GAM through chemical and substituent shifts, coupling constants and connectivities in COSY, NOESY, HETCOR and HBMC spectra. From NOESY spectra of GAM in DMSO-d6, it was concluded that the amide protons are oriented toward the ortho-proton at C-6. Obtained results indicate that the presence of the additional phenol group at C-5 in GAM favours the formation of intramolecular hydrogen bonding of the O...HO type between C2-OH proton and oxygen atom of the amide group.

Quantitative analysis of ginkgolic acids from Ginkgo leaves and products using 1H-NMR

The determination of ginkgolic acids in Ginkgo products is one of the principal components of quality control. However, a number of ginkgolic acids with different side chains may be present and this makes their analysis by conventional chromatographic methods more complex. In this study, 1H-NMR spectrometry was applied to the analysis of the total content of ginkgolic acids in leaves of Ginkgo biloba and in six types of commercial Ginkgo products in the absence of chromatographic purification. For this analysis, protons H-3, H-4, and H-5, which are well separated in the range 8 (ppm) 6.5-7.5 in the 1H-NMR spectrum, were utilised. For further confirmation, the correlations of H-3, H-4 and H-5 were examined by 1H-1H COSY spectra in all extracts. The quantity of the compounds was calculated from the relative ratio of the integral of each peak to the integral of the peaks of a known amount (100 microg) of anthracene used as an internal standard. The quantitative results obtained by 1H-NMR analysis were compared with those obtained by GC, which showed that the 1H-NMR method allows a simple quantification of total ginkgolic acids in Ginkgo extracts without any pre-purification steps.

[Fluorescence spectra and fluorescence quantum yield of sulfosalicylic acid]

Fluorescence spectra and fluorescence quantum yield of sulfosalicylic acid (SSA) have been studied. Under the condition of pH<2, SSA has no fluorescence. With the increase in pH value, fluorescence intensity of SSA increases. In the range of pH 5-10.5, SSA gives a strong and steady fluorescence with a maximum emission wavelength at 402 nm and excitation wavelengths at 212, 238 and 297 nm, respectively. In strong alkaline solutions with pH>13, SSA exists as another fluorescence species with a maximum excitation wavelength at 261 nm and a maximum emission wavelength at 390 nm. The excitation spectrum of SSA changes when its concentration is relatively higher, but the emission spectrum remains unchanged. There is an excellent linear relationship between fluorescence intensity and the concentration of SSA under neutral condition. The linear range is 5-250 ng x mL(-1), and the detection limit is 5 ng x mL(-1). Using quinine bisulphate as a reference, fluorescence quantum yields of SSA at different wavelengths were measured. At the maximum excitation wavelength 297 nm, fluorescence quantum yield of SSA is 0.54.

Sex Pheromone of Queens of the Slave-Making Ant, Polyergus breviceps

The sex attractant pheromone produced in mandibular glands of queens of the slave-making ant Polyergus breviceps has been identified as a blend of methyl 6-methylsalicylate and 3-ethyl-4-methylpentanol. In field trials, each compound alone was completely unattractive to males, whereas blends of the two compounds attracted hundreds of males within a couple of hours.

[Progress in research on constituents and pharmacological activities of sarcotestas of Ginkgo biloba]

The latest progress in research on constituents and pharmacological activities of sarcotestas of Ginkgo biloba has been studied. The main constituents in sarcotestas of G. biloba include flavones, ginkgolides, alkylphenols, polysaccharides and amino acids, etc. They show the following activities, such as bacteriostatic, bactericidal and pesticidal activities, antitumor and mutagenic, carcinogenic effects, antianaphylaxis and allergenic activity, effects on immunologic function, scavenging free radical, antisenile action, etc. The problems at present and the reseach direction for the future on sarcotestas of G. biloba have been put forward.

Quantification of allergenic urushiols in extracts of Ginkgo biloba leaves, in simple one-step extracts and refined manufactured material (EGb 761)

Extracts of leaves of Ginkgo biloba (family Ginkgoaceae), widely used in the treatment of peripheral and cerebral circulatory disorders as well as for dementia of different aetiology, contain long chain alkylphenols (with allergenic, cytotoxic, mutagenic and tumour-promoting properties) together with the extremely potent allergens, the urushiols. Such hazardous compounds can be present only in very low concentrations in phytopharmaceutical preparations and hence, for the purposes of drug safety, techniques must be available for the identification and quantification of these allergens at extremely low levels in refined manufactured materials. GC-MS analysis of samples collected at various stages during the production process of a standardised extract of G. biloba (EGb 761) demonstrated that all alkylphenols present in the primary acetone extracts were removed in parallel with the same efficiency irrespective of their aromatic substitution pattern. Furthermore, in the final product the content of urushiols was generally below the detection limit of 0.03 ppm. Therefore, it is concluded that demonstrating the absence of the predominant, and easily quantifiable, ginkgolic acids provides a reliable means for the control of pharmaceutical quality of the final product.

Gas chromatography-mass spectrometry with solid-phase microextraction method for determination of methyl salicylate and other volatile compounds in leaves of Lycopersicon esculentum

Methyl salicylate (MeSA) in many plants is a important signaling compound, which plays an important role in a pathogen-induced defense response. In this paper, gas chromatography-mass spectrometry (GC-MS) with headspace solid-phase microextraction (HS-SPME) was developed for determination of MeSA and other volatile compounds in leaves of a tomato plant (Lycopersicon esculentum). Tomato leaves were ground under liquid nitrogen and sampled by HS-SPME, with a 100 microm polydimethylsiloxane fiber, and finally analyzed by GC-MS. Eighteen compounds in the leaves of tomato plant infested by tobacco mosaic virus (TMV) were separated and identified, among them MeSA, which was quantitatively analyzed by the standard addition method. MeSA concentrations higher than 2.0 microg g(-1) fresh weight accumulated in leaves of TMV-infested tomato plant as the defense response to TMV. A similar concentration of MeSA in the leaves of MeSA-treated tomato plant was also found. No MeSA in leaves of control tomato plant was detected. These findings suggest that MeSA might be a signaling compound in the tomato plant response to TMV. The present method for determination of MeSA required only simple sample preparation and no organic solvent, and provided an excellent relative standard deviation of less than 5.0% and a low detection limit of 10 ng g(-1) fresh weight for MeSA. These results show that GC-MS-HS-SPME is a simple, rapid and sensitive method for determination of MeSA and other plant-signaling compounds in plant tissues.

Equilibrium Studies on Chromium(III) Complexes of Salicylic Acid and Salicylic Acid Derivatives in Aqueous Solution

The complexes of chromium(III) ion formed by salicylic acid, SA(H(2)L), and its derivatives (H(2)L): 5-nitrosalicylic acid (5-NSA), 5-sulphosalicylic acid (5-SSA) were investigated by means of potentiometry and spectroscopy, at 25 degrees C and in ionic strength of 0.1 M KNO(3) and 0.1 M KCl, respectively. Over the acidic pH range, the coordination of Cr(III) ion to SA and its derivatives in 1 : 1 mole ratio occurs, CrL(+) type complex is formed. In the excess of ligand, the coordination of the second ligand molecule is somewhat hindered; as a result CrL(HL) type complex occurs. Their existences were verified and their formation constants were determined. At near neutral pH, CrL(OH) and CrL(HL)(OH)(-) type hydroxo complexes formed by hydrolytic equilibria and their formation constants were also defined. The stabilities of Cr(III) complexes of SA and its derivatives decrease in the following order: SA>5-SSA>5-NSA. The formation constants of Cr(III) complexes of SA and its derivatives are in comparable ranges with the corresponding complexes of the 2,x-dihydroxybenzoic acid (2,x-DHBA) of Cr(III) ion. The stabilities of SA complexes for V(IV), Cr(III) and Fe(III) ions that have similar ionic radii, increase in the order VOL<CrL(+)<FeL(+). It is worthwhile noting that the binding ability of Cr(III) to salicylate ion is four orders of magnitude higher than to transferin, which is a blood serum protein and is associated with insulin action.

[Determination of ginkgolic acids in Ginkgo biloba extract and its preparations by high performance liquid chromatography]

AIM

To establish a high performance liquid chromatographic method for determination of ginkgolic acids in Ginkgo biloba extract and its preparations.

METHODS

Ginkgo biloba extract and its preparations were extracted with petroleum ether in Soxhlet apparatus, and then concentrated under vacuum. The ginkgolic acids were determined directly by HPLC, and identified by LC/DAD/ESI/MS. The chromatographic column was Inertsil ODS-2; the mobile phase was methanol-3% aqueous acetic acid(92:8); the flow rate was 1.0 mL.min-1; the column temperature was 40 degrees C; the detection wavelength was 310 nm.

RESULTS

There were six kinds of ginkgolic acid (C13:0, C15:1, C17:2, C15:0, C17:1 and an unknown compound C17:3 tentatively) in the Ginkgo biloba extract. The relative percentage content of ginkgolic acids C13:0, C15:1 and C17:1 was above 94%. The content of ginkgolic acids in Ginkgo biloba extract containing high content ginkgolic acids was 1.12%, and RSD was 2.4% (n = 5). The content of ginkgolic acids in one kind of EGb preparations (tablet) was 49.2 micrograms.g-1, and RSD was 4.3% (n = 5). The average recovery was 98.2%, RSD was 2.6% (n = 5).

CONCLUSION

The method is accurate, fast, simple, and can be used for determination of ginkgolic acids in Ginkgo biloba extract and its preparations.

Validation of a method for simultaneous determination of menthol and methyl salicylate in pharmaceuticals by capillary gas chromatography with cool on-column injection

The conditions for the identification and quantitative determination of menthol and methyl salicylate in ointment Balsamum Mentholi Compositum on a hydrocarbon-ester base (vaseline-lanolin), have been established by using capillary gas chromatography with cool on-column injection and flame ionization detection (FID). The good separation of menthol (tR = 7.2 min), methyl salicylate (tR = 8.7 min) and thymol (tR = 12.3 min) and camphor (tR = 6.0 min), used as alternative internal standards, beside vehiculum constituents (peak of tR = 15.8 min) was obtained. The method features a high sensitivity - detection limit for menthol and methyl salicylate was 0.1 ng and 5.0 ng, respectively, high accuracy, precision and recovery for active substances: 100.0% +/- 2.2%, when camphor was used as an internal standard.

Ovicidal and adulticidal effects of Eugenia caryophyllata bud and leaf oil compounds on Pediculus capitis

The toxicity of Eugenia caryophyllata bud and leaf oil-derived compounds (acetyleugenol, beta-caryophyllene, eugenol, alpha-humulene, and methyl salicylate) and congeners of eugenol (isoeugenol and methyleugenol) against eggs and females of Pediculus capitis was examined using direct contact application and fumigation methods and compared with those of the widely used delta-phenothrin and pyrethrum. In a filter paper diffusion bioassay with female P. capitis, the pediculicidal activity of the Eugenia bud and leaf oils was comparable to those of delta-phenothrin and pyrethrum on the basis of LT(50) values at 0.25 mg/cm(2). At 0.25 mg/cm(2), the compound most toxic to female P. capitis was eugenol followed by methyl salicylate. Acetyleugenol, beta-caryophyllene, alpha-humulene, isoeugenol, and methyleugenol were not effective. Eugenol at 0.25 mg/cm(2) was as potent as delta-phenothrin and pyrethrum but was slightly less effective than the pyrethroids at 0.125 mg/cm(2). Against P. capitis eggs, methyl salicylate and eugenol were highly effective at 0.25 and 1.0 mg/cm(2), respectively, whereas little or no activity at 5 mg/cm(2) was observed with the other test compounds as well as with delta-phenothrin and pyrethrum. In fumigation tests with female P. capitis at 0.25 mg/cm(2), eugenol and methyl salicylate were more effective in closed cups than in open ones, indicating that the effect of the compounds was largely due to action in the vapor phase. Neither delta-phenothrin nor pyrethrum exhibited fumigant toxicity. The Eugenia bud and leaf essential oils, particularly eugenol and methyl salicylate, merit further study as potential P. capitis control agents or lead compounds.

[Isolation and HPLC analysis of ginkgolic acid]

OBJECTIVE

To isolate ginkgolic acids (GA) from exopleura of Ginkgo biloba and to analyse GA.

METHODS

GA were ultrasonic-extracted from exopleura of Ginkgo biloba with petroleum ether, and purified by silica gel column chromatography. The content of GA in sample was determined by HPLC with methanol-3% acetic acid (90:10) as mobile phase at a flow rate of 1 ml/min. UV detection wavelength was set at 310 nm. A HiQ sil C18 column was used at 40 degrees C in analysis.

RESULTS

A good linearity was obtained in the range of 1.144-5.720 micrograms (r = 0.9978) for GA. The average recovery of GA was 97.50% with RSD of 1.70%.

CONCLUSION

The method may be employed to prepare GA from exopleura of Ginkgo biloba. The analysis method for GA is accurate and reliable, and can be used for determination of GA in sample.

Trade-off between synthesis of salicylates and growth of micropropagated Salix pentandra

We studied the relationship between biosynthesis of salicylates, the main chemical defenses in willow and growth of Salix pentandra by cultivating plants in the presence of 2-aminoindan-2-phosphonic acid (AIP), a powerful inhibitor of phenylalanine ammonia-lyase (PAL: EC 4.3.1.5.). AIP inhibited efficiently, though not totally, the endogenous synthesis of salicylates. This inhibition markedly increased plant growth. Exogenous application of the precursors of salicylates, benzoic acid (BA), salicylic acid (SA), and helicin, increased the levels of several individual salicylates, but decreased the growth of plants cultivated in the presence of AIP. These results suggest a trade-off between plant growth and the synthesis of salicylates in S. pentandra. Phenylalanine, which accumulated in response to inhibitor treatment, but was decreased by precursor treatments, may be a common and limiting precursor for both plant growth and salicylate synthesis. The biosynthesis of salicin is suggested to proceed mainly via benzoyl-glucose, an intermediate in the synthesis of salicylic acid. Salicin is the most obvious precursor of more substituted salicylates, salicortin, acetylsalicortin, and tremulacin. In addition, we found that the salicylate pools of mature plant parts of S. pentandra were not subject to turnover, implying that the maintenance of salicylates does not demand high resources of plants, although their initial construction is costly.

Ultraviolet-B radiation alters phenolic salicylate and flavonoid composition of Populus trichocarpa leaves

We investigated foliar phenolic composition of field- and greenhouse-grown Populus trichocarpa Torr. & A. Gray (black cottonwood) ramets subjected to near zero (0x), ambient (1x) or twice ambient (2x) concentrations of biologically effective ultraviolet-B (UV-B) radiation. After a 3-month treatment period, several age classes of foliage samples were harvested and the phenolic compounds extracted, separated by high performance liquid chromatography and identified and quantified by diode-array spectrometry and mass spectrometry. Foliar phenolic concentration was greater in 1x- and 2x-treated tissue than in 0x-treated tissue. Phenolic compounds that increased in response to UV-B radiation were predominantly flavonoids, primarily quercetin and kaempferol glycosides. Enhancement of UV-B radiation from 1x to 2x ambient concentration did not result in further flavonoid accumulation in either greenhouse or field ramets; however, a non-flavonoid phenolic glycoside, salicortin, increased in response to an increase in UV-B radiation from 1x to 2x ambient concentration. Increased salicortin concentrations accounted for at least 30-40% of the total (5%) increase in UV-absorption potential of 2x-treated tissue. Because salicortin and other salicylates are important in plant-herbivore-predator relationships, these increases are discussed in the context of collateral feeding studies. We conclude that enhanced solar UV-B radiation may significantly alter trophic structure in some ecosystems by stimulating specific phenolic compounds.

Interaction of nickel with 4-(2'-benzothiazolylazo) salicylic acid (BTAS) and simultaneous first-derivative spectrophotometric determination of nickel(II) and iron(III)

The solution properties of nickel complex with 4-(2'-benzo-thiazolylazo) salicylic acid (BTAS) have been studied by zero-order absorption spectrophotometry in 40% (v/v) ethanol at 20 degrees C and an ionic strength of 0.1 mol dm(-3) (KNO(3)). The equilibria that exist in solution were established and the basic characteristics of complexes formed were determined. A new direct spectrophotometric method for the determination of trace amounts of the nickel is proposed based on the formation of the Ni (BTAS) complex at pH 7.0. The absorption maximum, molar absorbtivity, and Sandell's sensitivity of 1:1 (M:L) complex are 525 nm, 0.6 x 10(4) l mol(-1) cm(-1) and 2.824 x 10(-9) microg cm(-2), respectively. The use of first-derivative spectrophotometry eliminates the interference of iron and enables the simultaneous determination of nickel and iron using BTAS. Quantitative determination of Ni(II) and Fe(III) is possible in the range (0.59-7.08) and (2.1-8.4) microg ml(-1), respectively with a relative standard deviation of 0.5%. The proposed method has been successfully applied to the simultaneous spectrophotometric determination of nickel and iron in steel alloys and aluminum alloys.

Carbonate ion-selective electrode with reduced interference from salicylate

A carbonate ion-selective electrode for determination of total carbon dioxide species such as carbon dioxide, bicarbonate and carbonate with reduced interference from salicylate is described. Derivatives of trifluoroacetophenone were used as neutral carriers for carbonate. A polymer-free liquid carbonate-selective membrane with a cellophane outer membrane was found to give a carbonate-selective electrode with a negligible response to salicylate. The electrical contact was obtained by insertion of a silver/silver chloride electrode directly into the liquid membrane. The electrode does not require any aqueous filling solution and is therefore maintenance-free. The response to carbon dioxide species was found to be highly reproducible with a response time of 1-2 min at total carbon dioxide concentrations in the range from 5 to 50 mM. The lifetime of the electrode was at least 3 months. The electrode is regarded as very promising for clinical analysis of carbon dioxide species in body fluids such as plasma and serum.

Is your patient taking the medicine? A simple assay to measure compliance with 5-aminosalicylic acid-containing compounds

BACKGROUND

Poor compliance with 5-aminosalicylic acid therapy has been reported amongst patients with inflammatory bowel disease. Currently, there is no easy method to monitor 5-aminosalicylic acid; however, the chemical similarity between 5-aminosalicylic acid and salicylate might provide a solution.

AIM

To determine the feasibility of using salicylate levels to monitor compliance with 5-aminosalicylic acid medication.

METHODS

Thirty-six patients with inflammatory bowel disease, taking maintenance 5-aminosalicylic acid, provided either a paired serum and urine sample or an intestinal biopsy. Samples were split into two: half were sent to the hospital biochemistry department for salicylate measurement, and half were analysed for 5-aminosalicylic acid and its metabolite, N-acetyl-5-aminosalicylic acid, using high performance liquid chromatography. Correlation between the results was calculated.

RESULTS

Serum and urine were available for 25 patients. Serum salicylate was undetectable, but urinary salicylate ranged from 31 to 3254 microg/mL. The correlations between urinary salicylate and 5-aminosalicylic acid and N-acetyl-5-aminosalicylic acid were 0.96 (95% confidence interval, 0.91-0.98) and 0.9 (95% confidence interval, 0.77-0.96), respectively. Sixteen biopsies were available from 13 patients. The 5-aminosalicylic acid and N-acetyl-5-aminosalicylic acid concentrations were 0.2-657 ng/mg and 1.6-1598 ng/mg, respectively; there was no correlation with bowel salicylate.

CONCLUSIONS

The close correlation between 5-aminosalicylic acid and salicylate levels offers a simple method to assess compliance with 5-aminosalicylic acid therapy.