A spectrophotometric assay for solid phase primary amino groups

A rapid, sensitive, and convenient spectrophotometric assay was developed for the measurement of amino groups on solid supports. This method is based on the reaction of amino groups of solids with an excess ofo-phthaldialdehyde (OPA) and subsequent quantitative determination of unreacted OPA by reaction with glycine. Four solids possessing variable quantities of amino groups were examined. Results indicate that about 70% of the total surface amino concentration (determined by the microKjeldahl method) are available for ligand attachment. Unlike the spectrophotometric 2,4,6-trinitrobenzenesulfonic acid method, the OPA spectrophotometric assay is more rapid, sensitive, and convenient, and unlike the spectrofluorimetric OPA, it does not require sophisticated instrumentation.     

Bioactive steroidal glycosides from the marine sponge Erylus lendenfeldi

Bioassay-guided fractionation of the methanol extract of Erylus lendenfeldi using engineered strains of budding yeast (Saccharomyces cerevisiae) has resulted in the isolation of the known compound eryloside A (1) and two new compounds, erylosides K (2) and L (3). The structures were established based mainly on 1D and 2D NMR data. The absolute stereochemistry of eryloside A, which had never been fully characterized, was determined using the modified Mosher's method. The absolute stereochemistry of eryloside K was determined by comparison with tetrahydroeryloside A. Compounds 1-3 exhibited selective cytotoxicity against a yeast strain (Δrad50) deficient in double strand break (DSB) repair.     

Heterogeneous and homogeneous electrochemiluminoimmunoassays of hTSH at disposable oxide-covered aluminum electrodes

Heterogeneous and homogeneous immunoassays of human thyroid stimulating hormone (hTSH) were developed on immunometric basis using aromatic Tb(III) chelates as electrochemiluminescent labels and varied types of disposable oxide-covered aluminum electrodes as the solid phase of the immunoassays. The long luminescence lifetime of the present labels allows the use of time-resolved electrochemiluminescence detection and provide the low detection limits of these labels and, thus, sensitive immunoassays. The primary antibody of immunometric immunoassays was coated upon aluminum oxide surface by physical absorption. In homogeneous immunoassays using 66 μl cell and 15 min incubation time, a linear calibration range of 0.25-324 μU/ml was obtained by applying only a single cathodic excitation pulse in the detection step of the assay.     

A Stability-Indicating LC Method for Candesartan Cilexetil

An isocratic reversed-phase liquid chromatographic method has been developed for quantitative determination of candesartan cilexetil, used to treat hypertension, in the bulk drug and in pharmaceutical dosage forms. The method is also applicable to analysis of related substances. Chromatographic separation was achieved on a 250 mm × 4.6 mm, 5 μm particle, CN column with a 50:50 (v/v) mixture of phosphate buffer, pH 3.0, and acetonitrile as mobile phase. The flow rate was 1.0 mL min⁻¹ and the detection wavelength was 210 nm. Resolution of candesartan cilexetil and six potential impurities was greater than 2.0 for all pairs of compounds. The drug was subjected to hydrolytic, oxidative, photolytic, and thermal stress and substantial degradation occurred in alkaline and acidic media and under oxidative and hydrolytic stress conditions. The major product obtained as a result of basic hydrolysis was different from that produced by acid hydrolysis and aqueous hydrolysis. The stress samples were assayed against a reference standard and the mass balance was found to be close to 99.6%. The method was validated for linearity, accuracy, precision, and robustness.     

A simple colorimetric method for the assay of penicillin G salt and penicillamine by oxidation with iodate

A simple colorimetric procedure is described for determination of penicillin G salt and penicillamine. It is based on oxidation with potassium iodate at room temperature and measurement of the liberated iodine at 520 nm after extraction with carbon tetrachloride. Compared with other procedures, this method proved to be more rapid, highly reproducible and reasonably accurate. The relative standard deviation did not exceed 0.9% and 0.4% for penicillin and penicillamine, respectively. The procedure has been successfully applied to pharmaceutical preparations containing either of the two compounds.     

On-line preconcentration and determination of nickel in natural water samples by flow injection-inductively coupled plasma optical emission spectrometry (FI-ICP-OES)

An on-line nickel preconcentration and determination system implemented with inductively coupled plasma optical emission spectrometry (ICP-OES) associated to flow injection (FI) was studied. Trace amounts of nickel were preconcentrated by sorption on a conical minicolumn packed with activated carbon (AC) at pH 5.0. The nickel was removed from the minicolumn with 20% nitric acid. An enrichment factor of 80-fold for a sample volume of 50 ml was obtained. The detection limit (DL) value for the preconcentration method proposed was 82 ng l⁻¹. The precision for ten replicate determinations at the 0.5 μg l⁻¹ Ni level was 3.0% relative standard deviation (R.S.D.), calculated from the peak heights obtained. The calibration graph preconcentration method for nickel was linear with a correlation coefficient of 0.9997 at levels near the detection limits (DL) up to at least 100 μg l⁻¹. The method was successfully applied to the determination of nickel in natural water samples.     

On-line solvent evaporator for coupled LC systems

The mobile phase of a fraction eluted from a first LC column is removed by an on-line evaporator in order to reconcentrate the solute material or to exchange the eluent before performing a subsequent LC separation. Evaporation essentially occurs by concurrent evaporation, i.e. the solvent evaporates at a rate equal to the flow rate of the incoming eluent, and is driven by the overflow principle, i.e. vapors leave the tube as a result of the expansion resulting from evaporation. The liquid is introduced into a small tube (e.g., 4 cm × 1.3 mm i.d.) which is packed, e.g., with a coarse silica gel. The outlet of the evaporator is connected to vacuum in order to enable evaporation at reduced temperature and to increase retention of the volatile components. With normal phase eluents, evaporation rates may approach 1 ml/min; n-dodecane was the most volatile n-alkane fully retained by the evaporator.     

基于钴离子介导信号转换的抗坏血酸比色分析

抗坏血酸是许多生化过程所必需的一种生物小分子。借助于羟基氧化钴纳米片的氧化性和钴离子与硫氰酸根离子之间强的螯合作用,本文报道了一种基于钴离子介导信号转换的新方法用于抗坏血酸的比色分析。在抗坏血酸存在时,羟基氧化钴纳米片被还原降解产生二价钴离子,钴离子与硫氰酸根离子之间通过螯合作用生成蓝色的阴离子络合物[Co(NCS)₄]^2-,在625nm处产生可见吸收信号。在优化条件下,体系625nm处的吸收值与抗坏血酸浓度在0.03～0.45 mmol/L范围内呈良好的线性关系,线性方程为A₆₂₅=0.638c(mmol/L)+0.042,相关系数R=0.993,检测限(3S/N)为1.5μmol/L。     

Evaluation of the In Vitro Wound-Healing Potential of Ayahuasca

Ayahuasca is an Amazonian drink, which contains β-carboline alkaloids and N,N-dimethyltryptamine. The aim of this study was to evaluate the healing potential of decoctions of a commercial mixture, four individual plants and four mixtures of two plants used in the ayahuasca preparation. Thus, the cytotoxic potential of the samples was evaluated and a wound-healing assay was performed with a NHDF cell line. Subsequently, a parallel artificial membrane permeability assay was also performed, to verify if any psychoactive compound could be absorbed by skin fibroblasts. The integrity and permeability of the cell layer were also evaluated, using the transepithelial electrical resistance assay and Lucifer yellow permeability assay, respectively. The compounds absorbed by the cell layer were quantified by high-performance liquid chromatography coupled to a diode array detector. The results showed that only one sample showed cytotoxicity and all the others promoted the migration of skin fibroblasts. Additionally, it was also verified that β-carbolynic alkaloids and N,N-dimethyltriptamine were not absorbed by the cell layer, and in general, did not interfere with its permeability and integrity. To the best of our knowledge, this is the first study where ayahuasca’s wound-healing potential was evaluated.     

Design and Synthesis of Coumarin Derivatives as Cytotoxic Agents through PI3K/AKT Signaling Pathway Inhibition in HL60 and HepG2 Cancer Cells

In this study, a series of coumarin derivatives, either alone or as hybrids with cinnamic acid, were synthesized and evaluated for their cytotoxicity against a panel of cancer cells using the MTT assay. Then, the most active compounds were inspected for their mechanism of cytotoxicity by cell-cycle analysis, RT-PCR, DNA fragmentation, and Western blotting techniques. Cytotoxic results showed that compound (4) had a significant cytotoxic effect against HL60 cells (IC₅₀ = 8.09 µM), while compound (8b) had a noticeable activity against HepG2 cells (IC₅₀ = 13.14 µM). Compounds (4) and (8b) mediated their cytotoxicity via PI3K/AKT pathway inhibition. These results were assured by molecular docking studies. These results support further exploratory research focusing on the therapeutic activity of coumarin derivatives as cytotoxic agents.