A Valid High Performance Liquid Chromatography Method for Quantification of Luteinizing Hormone Releasing Hormone

Advances and perspectives in the analytical technology for small peptide hormones analysis: A glimpse to gonadorelin

In the last twenty years, we have witnessed an important evolution of bioanalytical approaches moving from conventional lab bench instrumentation to simpler, easy-to-use techniques to deliver analytical responses on-site, with reduced analysis times and costs. In this frame, affinity reagents production has also jointly advanced from natural receptors to biomimetic, abiotic receptors, animal-free produced. Among biomimetic ones, aptamers, and molecular imprinted polymers (MIPs) play a leading role. Herein, our motivation is to provide insights into the evolution of conventional and innovative analytical approaches based on chromatography, immunochemistry, and affinity sensing referred to as peptide hormones. Indeed, the analysis of peptide hormones represents a current challenge for biomedical, pharmaceutical, and anti-doping analysis. Specifically, as a paradigmatic example, we report the case of gonadorelin, a neuropeptide that in recent years has drawn a lot of attention as a therapeutic drug misused in doping practices during sports competitions.

Peptide loaded polymeric nanoparticles by non-aqueous nanoprecipitation

It is always a challenge to encapsulate water-soluble peptides in polymer nanoparticle (NP) systems. We establish and validate our newly developed non-aqueous nanoprecipitation method to encapsulate neuro-peptides drugs such as oxytocin and Luteinizing hormone-releasing hormone (LHRH) in poly(sebacic anhydride) (PSA) NPs. NPs were prepared by a solvent-antisolvent process under a strict anhydrous environment to obtain high drug loading and to avoid premature PSA degradation and drug release. Dynamic light scattering (DLS) and Scanning Electron Microscopy (SEM) reveal the size for both drug loaded PSA NPs to ∼ 300 nm. The drug loaded NPs were dispersible and spherical in shape with uniform morphology. The in vitro release profile of oxytocin from PSA NPs occurs with the burst release of ∼ 50% within the first hour in the aqueous release medium, whereas LHRH release is comparatively slow. Thus, looking into the fast degrading properties of PSA and drug release behavior, the developed NPs can be used for direct delivery of the neuropeptides to the olfactory epithelium using a refillable nasal atomizer that deposits mist onto the olfactory neuro-epithelium. We also applied our developed method to prepare NPs of poly(lactic-co-glycolic acid) (PLGA), polylactic acid (PLA), and poly(ε-caprolactone) (PCL). A Thyrotropin releasing hormone (TRH) was used as the sample neuropeptide drug to validate our non-aqueous method. The results reveal the formation of TRH loaded PLGA, PLA and PCL NPs with 100% drug loading. TEM analysis shows the formation of spherical NPs, having similar release properties as those of PSA NPs. Overall, we report that our developed method is suitable for co-encapsulating hydrophilic drugs in polymer NPs with high drug loading and release properties.

Isocratic liquid chromatographic assay for monitoring the degradation of luteinizing hormone releasing hormone by extracts from the gastrointestinal tract of possums

A simple HPLC method to separate human luteinizing hormone releasing hormone (LHRH) from its metabolites using an isocratic elution is described. Intact LHRH and five metabolites were separated in 11.4 min. The calibration curve (peak area versus concentration) was linear over the concentration range 1.25-35 microg/ml (r(2)=0.99) with the intercept not significantly different from zero (P>0.05). Intra-day and inter-day variability of the assay was less than 5% for repeat injections of 5, 14.5 and 29 microg/ml. The method was applied to evaluate the susceptibility of LHRH to enzymes present in the lumen and mucosal extracts of the gastrointestinal tract of possums. The major degradation products of LHRH were identified by HPLC separation, amino acid analysis and mass spectrometry as LHRH (1-5), LHRH (1-4), LHRH (1-3) and LHRH (3-4).

Stability of luteinizing hormone releasing hormone: effects of pH, temperature, pig skin, and enzyme inhibitors

The purpose of this investigation was to determine the stability of luteinizing hormone releasing hormone (LHRH) as a function of solution pH, temperature, and pig skin with and without enzyme inhibitors. LHRH, incubated with a 0.1 M phosphate buffer (pH 2.5-8.1), pig skin, and pig skin with enzyme inhibitors, was analyzed using reversed-phase high performance liquid chromatography. The solution's pH affected the rate constants of LHRH, following apparent first-order kinetics. Maximum stability was achieved at pH 6.05. Therefore, the effect of various temperatures (i.e., 65, 75, 80, and 90 degrees C) was studied on the stability of LHRH at pH 6.05. The activation energy for the overall reaction was 23.4 kcal/mol at pH 6.05. The shelf-life of LHRH at 25 degrees C and pH 6.05, calculated using the Arrhenius equation, was approximately 4 years. The rate constant of LHRH in the skin (area: 9 cm2; thickness: 0.5 mm) was 0.167 hr-1. Out of three inhibitors (i.e., aprotinin, bestatin, and leupeptin), bestatin had the best stabilizing effect on the degradation of LHRH by the skin. The rate constant of LHRH in the presence of bestatin was 0.082 hr-1. Sixty percent of LHRH was found to be degraded in the skin within 5 hr in the absence of enzyme inhibitors, whereas only 33% of LHRH was degraded in the presence of bestatin (an aminopeptidase inhibitor).

Chromatography of guanidino compounds

Guanidino compounds involved in the urea and guanidine cycles have been found in serum of nephritic patients, and some guanidino compounds have been suspected to be uremic toxins. The simultaneous analysis of naturally occurring metabolites is important for diagnosis of diseases. In this review, liquid chromatographic analysis of natural metabolites of guanidino compounds are described. the information about arginine as a precursor of nitric oxide are included. The reports of pharmaceutical compounds having a guanidino group, peptides containing arginine and aminoglycosides are summarized in Table 1.