Determination of salicylic acid and its metabolites in urine by derivative synchronous spectrofluorimetry

Curcumin-Cu(II) Ensemble-Based Fluorescence "Turn-On" Mode Sensing the Plant Defensive Hormone Salicylic Acid In Situ and In Vivo

Salicylic acid (SA), a crucial, plant-derived signal molecule, is capable of launching global transcriptional reprogramming to assist plants in obtaining the systemic acquired resistance (SAR) mechanism. Thus, the accurate detection of SA will not only significantly contribute to the understanding of the plant SAR but also contribute to crop protection and to the security of the agricultural production and food supply. However, detection of SA using fluorescent probes is a great challenge for scientists, because SA analogues can significantly interfere with the detection results. Herein, we first reported using a simple, natural curcumin-Cu²⁺ ensemble to selectively and sensitively monitor SA in situ and in vivo, directed by a fluorescence "turn-on" mode. A binary combination curcumin-Cu²⁺ was first fabricated with a fluorescence "turn-off" pattern caused by the paramagnetic nature of Cu²⁺. Subsequently, a fluorescence "turn-on" response was performed for detecting SA accompanied by the formation of the ternary complex curcumin-Cu²⁺-SA due to the high affinity of SA toward Cu²⁺, which reduced the fluorescent impact caused by the paramagnetism of Cu²⁺. Further study revealed that the rationally designed hybrid probe could monitor SA in living cell lines. We anticipate that this finding can inspire the discovery of a high-performance SA probe.

Highly Selective and Sensitive Detection of Biogenic Defense Phytohormone Salicylic Acid in Living Cells and Plants Using a Novel and Viable Rhodamine-Functionalized Fluorescent Probe

Detecting plant-derived signal molecules using fluorescent probes is a key topic and a huge challenge for scientists. Salicylic acid (SA), a vital plant-derived defense hormone, can activate global transcriptional reprogramming to systemically express a network of prominent pathogenesis-related proteins against invasive microorganisms. This strategy is called systemic acquired resistance (SAR). Therefore, monitoring the dynamic fluctuations of SA in subcellular microenvironments can advance our understanding of different physiological and pathological functions during the SA-induced SAR mechanism, thus benefiting the discovery and development of novel immune activators that contribute to crop protection. Here, detection of signaling molecule SA in plant callus tissues was first reported and conducted by a simple non-fluorescent rhodamine-tagged architecture bearing a flexible 2-amino-N,N-dimethylacetamide pattern. This study can markedly advance and promote the usage of fluorescent SA probes for distinguishing SA in the plant kingdom.

Application of time-resolved fluorescence to the determination of metabolites

A simple fluorescent methodology for the simultaneous determination of two major metabolites of acetylsalicylic acid--salicylic and gentisic acids--in pharmaceutical preparations and human urine is proposed. Due to the overlapping between the fluorescence spectra of both analytes, the use of the more selective fluorescence decay curves is proposed. Values of dependent instrumental variables affecting the signal-to-noise ratio were fixed with a simplex optimization procedure. A calibration matrix of thirteen standards plus two blank samples was processed using a partial least-squares (PLS) analysis. To assess the goodness of the proposed method, a prediction set of nine synthetic samples was analyzed, obtaining recovery percentages between 95% and 106%. Limits of detection, calculated by means of a new criterion, were 3.49 μg L(-1) and 1.66 μg L(-1) for salicylic and gentisic acids, respectively. The method was also tested in three pharmaceutical preparations containing salicylic acid, obtaining recovery percentages close to 100%. Finally, the simultaneous determination of both analytes in human urine samples was successfully carried out by the PLS-analysis of a matrix of thirteen standards plus five analyte blanks. Although spectra of analytes and urine overlap strongly, no extraction method neither prior separation of the analytes were needed.

Combined liquid and solid-surface room temperature fluorimetric determination of naproxen and salicylate in serum

A rapid and sensitive method for the determination of naproxen and salicylate in serum is presented. The employed strategy combines solid-phase extraction on a reverse-phase membrane with spectrofluorimetry. Solid-phase extraction under optimum pH conditions makes NX to be retained over the solid surface (where it is directly determined by a fluorimetric technique). Salicylate passes through the disk and is also fluorimetrically determined, but in solution. The linear calibration ranges for NX in the membrane and salicylate in solution were 0.014-0.250 and 0.010-0.250 microg ml(-1), respectively. The lowest value, in each case, is the corresponding limit of quantitation. The performance of the method is demonstrated with the successful determination of both drugs in spiked and real human serum samples.

Simultaneous determination of salicylamide and salsalate in serum and urine by first derivative variable-angle synchronous fluorescence spectrometry

The determination of salicylamide and salsalate in human serum and urine is performed using a simple, rapid, sensitive, and selective method. The broad-band overlapping conventional spectra of both compounds are resolved by means of first derivative variable-angle synchronous fluorescence spectrometry. The method is based on the intrinsic fluorescence of both drugs in chloroformic solution. The measurements are performed in an alkaline medium, which is adjusted by adding 0.40 M pyrrolidine chloroformic solution to the organic phase. The method was applied for the simultaneous determination of salicylamide and salsalate, at concentrations between 0.100 and 1. 000 microg mL-1 for both components, by means of absolute values of a first derivative variable-angle synchronous scan at the emission/excitation wavelengths of 410/299 nm for salicylamide and 440/307 nm for salsalate. Serum and urine are extracted with chloroform, by adding acetate buffer solution to provide pH 4.8 in the aqueous phase. Finally, pyrrolidine chloroformic solution is added to organic phase, where both components are determined, without the need for a reextraction step to an aqueous phase.

Selective determination of naproxen in the presence of nonsteroidal anti-inflammatory drugs in serum and urine samples using room temperature liquid phosphorimetry

A very simple, rapid and highly sensitive method is described for determining naproxen in serum and urine. This method is based on room temperature phosphorescence of naproxen in sodium dodecylsulphate micelles, with thallium(I) providing the external heavy atom and sodium sulphite acting as the oxygen scavenger. Under the optimum and experimental conditions, the range of application is 0.09-4.5 micrograms ml-1 and the limit of detection is 0.03 micrograms ml-1. The most relevant characteristic of this method is its great selectivity, e.g. naproxen can be determined in the presence of other nonsteroidal anti-inflammatory drugs (NSAIDs). The clinical applicability of this procedure has been tested, analysing naproxen in serum and urine samples. The analytical recoveries and inter- and intra assay precision data obtained demonstrate the usefulness of this procedure when used with very complex samples.

Micellar-enhanced synchronous-derivative fluorescence determination of derivatized folic acid in pharmaceutical preparations

A sensitive and inexpensive micellar-enhanced synchronous-derivative spectrofluorimetric method is described for the determination of folic acid in pharmaceutical preparations. The method is based upon derivatization of the vitamin with fluorescamine in acid solution and enhancement of the fluorescence with a surfactant. Linear fluorimetric analytical curves were obtained for folic acid concentrations of 0.05-6 micrograms ml-1 (detection limit 0.012 micrograms ml-1); the RSD for 1 micrograms ml-1 of folic acid was 2.82%. The method has been applied to the determination of folic acid synthetic mixtures and pharmaceutical preparations.