Novel high throughput green UPLC-MS/MS methods for determination of desmopressin with special sample handling

Objectives of present investigation were to develop novel high throughput green UPLC-MS/MS methods for quality control of desmopressin formulations. Two liquid chromatographic methods: Method-I based on isocratic elution and method-II based on gradient elution were developed and validated. Methods were green, since less amount of organic solvent (≤75 ​μL, per sample run time) was utilized in mobile phase. Mobile phase (0.1% formic acid in ACN, and in water), flow rate was 300 ​μL/min. Desmopressin retention time and sample run time for Method-I were 0.59 and 1.0 ​min, respectively. Retention time and sample run time for method-II were 2.03 and 2.5 ​min, respectively. Double charged ions [M ​+ ​2H]²⁺ of desmopressin (m/z 535.33 ​> ​120) were monitored in multi-reaction monitoring mode. Desmopressin was directly analyzed in water samples. Calibration curves were prepared between 50 and 600 ​ng/mL. The values of r² were 0.999. Assay and dissolution study of desmopressin formulation was successfully performed using these methods. Desmopressin was found to adsorb or react with different type of materials while handling. The specific filters (Chromafil® Xtra PTFE-45/25 0.45 ​μm, syringe filter) and tubes (glass tubes or Neutral graduated micro test tubes) were used for handling desmopressin samples.     

New Sugar‐Based Permeant Analogs of D‐Myo‐Inositol 1,4,5‐Trisphosphate Mimicking the Effect of Vasopressin: Synthesis and Biologic Evaluation*

On the basis of the xylose‐inositol analogy, a series of permeant analogs of D‐myo‐inositol 1,4,5‐trisphosphate (InsP₃) have been synthesized by various esterifications of the phosphate groups. Their ability to cross the cell membrane has been tested on vasopressin cells. Very fast liberation of calcium occurs when active analogs are introduced in the extracellular medium on intact cells. Membrane crossing as well as hydrolysis of the phosphate is very rapid using acyloxymethyl esterification of all the phosphate groups. The free compounds behave in the cell like InsP₃. One of the analogs prepared this way behaves like vasopressin for rat hepatocyte cells expressing vasopressin receptor.     

Pyrazolo[1,4]diazepines as non-peptidic probes of the oxytocin and vasopressin receptors

An improved synthesis of differently substituted pyrazolo[1,4]diazepine compounds is reported. In addition, we have used this methodology to obtain non-peptidic compounds to probe the oxytocin and vasopressin receptors.     

Preparation of triazolobenzodiazepine derivatives as Vasopressin V1a antagonists

This Letter describes the synthesis of a number of fused tricyclic and bicyclic triazolobenzodiazepines for the Vasopressin V1a antagonist programme.     

Peptide drug carrier: studies on incorporation of vasopressin into nano-associates comprising poly(ethylene glycol)-poly( -aspartic acid) block copolymer

To fabricate peptide delivery systems using polymeric drug carriers, an oligopeptide model drug, [Arg⁸]-vasopressin(AVP), was incorporated into nano-associates comprising poly(ethylene glycol)-( -aspartic acid block copolymer (PEG-P(Asp)). Incorporation of the AVP was accomplished using a dialysis method. Static light scattering measurements revealed that the acid-type and mixture-type PEG-P(Asp)s formed nano-associates independently without AVP, while the salt form PEG-P(Asp) did not. High loading of AVP into acid-type PEG-P(Asp) was observed with loading levels controlled by changing the molar ratio of drug and block copolymer. Mixture-type PEG-P(Asp) did not show high loading and the salt-type PEG-P(Asp) form did not at all. Acid-type P(Asp) homopolymer formed associates including AVP, however, it was insoluble in aqueous medium. Dynamic light scattering measurements showed that the acid-type PEG-P(Asp) associates sizes narrowly clustered around 150 nm. This finding suggests that associates of acid-type PEG-P(Asp) effectively incorporates peptides possibly via a hydrogen bonding interaction between the block copolymer and the peptide.     

Label-free electrochemical monitoring of vasopressin in aptamer-based microfluidic biosensors

Vasopressin is an indicating biomarker for blood pressure in the human body and low vasopressin levels can be indicative of late-phase hemorrhagic shock or other traumatic injuries. In this paper we have developed an aptamer-based label-free microfluidic biosensor for the electrochemical detection of vasopressin. The detection area consists of aptamers immobilized on carbon nanotubes which specifically capture the vasopressin molecules in solution resulting in changes in conductivity across the sensor. We report a limit of detection of 43 pM in standard solutions and demonstrate high detection specificity toward vasopressin when different interferents are present. The miniaturized microfluidic biosensor offers continuous monitoring of different vasopressin levels with good potential for portability. Ultimately such a system could serve as a point-of-care diagnostics tool for patients with excessive bleeding when standard medical infrastructure is not available.     

Theoretical studies of the mechanism of the action of the neurohypophyseal hormones. I. Molecular electrostatic potential (MEP) and molecular electrostatic field (MEF) maps of some vasopressin analogues

Summary Continuing our theoretical studies of the oxytocin and vasopressin analogues, we have analysed the molecular electrostatic potential (MEP) and the norm of the molecular electrostatic field (MEF) of [1--mercaptopropionic acid]-arginine-vasopressin ([Mpa¹]-AVP), [1-(-mercapto-,-cyclopentamethylene)propionic acid]-arginine-vasopressin ([Cpp]-AVP), and [1-thiosalicylic acid]-arginine-vasopressin ([Ths]-AVP) whose low-energy conformations were calculated in our previous work. These compounds are known from experiment to exhibit different biological activity. The scalar fields mentioned determine the energy of interaction with either charged (MEP) or polar (MEF) species, the energy being in the second case either optimal or Boltzmann-averaged over all the possible orientations of the dipole moment versus the electrostatic field. The electrostatic interactions slowly vanish with distance and can therefore be considered to be the factor determining the molecular shape at greater distances, which can help in both predicting the interactions with the receptor at the stage of remote recognition and in finding the preferred directions of solvation by a polar solvent. In the analysis of the fields three techniques have been used: (i) the construction of maps in certain planes; (ii) the construction of maps on spheres centered in the charge center of the molecule under study and of poles chosen according to the main axes of the quadrupole moment; and (iii) the construction of surfaces corresponding to a given value of potential. The results obtained show that the shapes of both MEP and MEF are similar in the case of [Mpa¹]-AVP and [Cpp¹-AVP (biologically active), while some differences emerge when comparing these compounds with [Ths¹]-AVP (inactive). It has also been found that both MEP and MEF depend even more strongly on conformation.     

Application of copper(II)-mediated radical cross-dehydrogenative coupling to prepare spirocyclic oxindoles and to a formal total synthesis of Satavaptan

Application of radical cross-dehydrogenative coupling (CDC) procedures to prepare a range of novel spirocyclic oxindoles and to a formal total synthesis of the vasopressin V₂ receptor antagonist Satavaptan is reported. The key step involves a copper-mediated oxidative cyclisation of a simple linear anilide precursor to give the spirocyclic oxindole core. This synthetic approach was also used to prepare novel Satavaptan scaffolds and analogues.