Synthesis and biological activities of local anesthetics

Experimental study of local anesthetic and antiarrhythmic activities of fluorinated ethynylpiperidine derivatives

The chemical structure of piperidine has a unique ability to combine with other molecular fragments. This fact makes it possible to actively use it as an effective basis for the creation of new drug-like substances. Thus, the aim of the current investigation was to study the acute toxicity, local anesthetic potency, and antiarrhythmic activity of the two new synthesized piperidine derivatives under laboratory codes LAS-286 and LAS-294 (local anesthetic substances). The Bulbring & Wajda animal model and method of determining the nociception threshold during electrical stimulation was used to investigate the action of the substance during infiltration anesthesia. An antiarrhythmic activity was observed by the aconitine-induced rat arrhythmia model. Additionally, these compounds were studied in relation to molecular docking to delineate the structure-activity relationships. The tested piperidine derivatives had a low toxicity in the subcutaneous and intravenous administration routes. The experimental results showed a higher prolonged and pronounced local anesthetic activity for LAS-286 at a 0.5% concentration, compared to the reference preparations. The low dosage of 0.1 mg/kg of LAS-294 demonstrated a pronounced preventive antiarrhythmic effect in 90% of cases on the development of mixed arrhythmia, caused by aconitine. The results of molecular docking confirmed a higher binding affinity of the tested piperidines with the Nav1.4 and Nav1.5 macromolecules. The results of the present study are very promising, because these piperidines have shown a high biological activity, which can suggest a potential therapeutic application in the future.

Dereplication of tropane alkaloids from four Erythroxylum species using liquid chromatography coupled with ESI-MSn and HRESIMS

RATIONALE

Tropane alkaloids represent an important class of secondary metabolites, but many of these compounds are already described in the scientific literature, so the use of guided identification and isolation strategies, such as dereplication, represent a fast and safe alternative.

METHODS

For the annotation of the tropane alkaloids the chloroform phases of the four Erythroxylum species were analyzed by high-performance liquid chromatography coupled to mass spectrometry with positive-mode electrospray ionization, then the ions of their protonated molecules, molecular formulas and fragmentation patterns were observed and a comparison of the obtained data with those present in the scientific literature was performed. The compounds not fully annotated were isolated and characterized by 1 H and 13 C nuclear magnetic resonance spectroscopy.

RESULTS

The annotation of 29 tropane alkaloids was performed, some being described for the first time in the family Erythroxylaceae. The chemical profiles of these secondary metabolites in the four Erythroxylum species analyzed were traced and compared. Isolation of three compounds whose mass spectral data were not sufficient for their full annotation was performed. They were 6-(benzoyloxy)-3-(3,5-dimethoxy-4-hydroxybenzoyloxy)tropane, 6-(benzoyloxy)-3-(3,4,5-trimethoxybenzoyloxy)tropane and 6-(benzoyloxy)-3-(3,4,5-trimethoxycinamoyloxy)tropane, first reported in the species Erythroxylum revolutum Mart.

CONCLUSIONS

This work contributes to the phytochemical knowledge of the genus Erythroxylum, and demonstrates the efficiency and importance of using guided isolation methodologies of secondary metabolites in natural products research. Since safe results were presented in the annotation of the compounds evidenced, employing small quantities of organic solvents, when compared to classical methodologies, besides promoting an optimization in the research time.

Role and Recent Advancements of Ionic Liquids in Drug Delivery Systems

Advancements in the fields of ionic liquids (ILs) broaden its applications not only in traditional use but also in different pharmaceutical and biomedical fields. Ionic liquids "Solutions for Your Success" have received a lot of interest from scientists due to a myriad of applications in the pharmaceutical industry for drug delivery systems as well as targeting different diseases. Solubility is a critical physicochemical property that determines the drug's fate at the target site. Many promising drug candidates fail in various phases of drug research due to poor solubility. In this context, ionic liquids are regarded as effective drug delivery systems for poorly soluble medicines. ILs are also able to combine different anions/cations with other cations/anions to produce salts that satisfy the concept behind the ILs. The important characteristics of ionic liquids are the modularity of their physicochemical properties depending on the application. The review highlights the recent advancement and further applications of ionic liquids to deliver drugs in the pharmaceutical and biomedical fields.

Local anesthetics via multicomponent reactions

Local anesthetics occupy a prime position in clinical medicine as they temporarily relieve the pain by blocking the voltage-gated sodium channels. However, limited structural diversity, problems with the efficiency of syntheses and increasing toxicity, mean that alternative scaffolds with improved chemical syntheses are urgently needed. Here, we demonstrate an MCR-based approach both towards the synthesis of commercial local anesthetics and towards novel derivatives as potential anesthesia candidates via scaffold hopping. The reactions are efficient and scalable and several single-crystal structures have been obtained. In addition, our methodology has been applied to the synthesis of the antianginal drug ranolazine, via an Ugi three-component reaction. Representative derivatives from our libraries were evaluated as neuronal activity inhibitors using local field potential recordings (LFPs) in mouse hippocampal brain slices and showed very promising results. This study highlights new opportunities in drug discovery targeting local anesthetics.

Synergistic Interaction and Binding Efficiency of Tetracaine Hydrochloride (Anesthetic Drug) with Anionic Surfactants in the Presence of NaCl Solution Using Surface Tension and UV–Visible Spectroscopic Methods

Surfactants are ubiquitous materials that are used in diverse formulations of various products. For instance, they improve the formulation of gel by improving its wetting and rheological properties. Here, we describe the effects of anionic surfactants on an anesthetic drug, tetracaine hydrochloride (TCH), in NaCl solution with tensiometry and UV–visible techniques. Various micellar, interfacial, and thermodynamic parameters were estimated. The outputs were examined by using different theoretical models to attain a profound knowledge of drug–surfactant mixtures. The presence of attractive interactions among drug and surfactant monomers (synergism) in mixed micelle was inferred. However, it was found that sodium dodecyl sulfate (SDS) showed greater interactions with the drug in comparison to sodium lauryl sarcosine (SLS). The binding of the drug with surfactants was monitored with a spectroscopic technique (UV–visible spectra). The results of this study could help optimize the compositions of these mixed aggregates and find the synergism between monomers of different used amphiphiles.

Cocaine: from a controlled drug by the DEA to an approved drug by the FDA

Abstract:

NumbrinoTM, a nasal anesthetic solution based on cocaine hydrochloride, was recently approved by the FDA for diagnostic procedures and surgery – now, what will be the role of the controlling agencies and the legislation of producing countries to face the imminent medicinal use of cocaine? Would chemistry be the protagonist in proposing alternative approaches to help and overcome this issue? The debate is open with this commentary

Mixed Micellization, Thermodynamic and Adsorption Behavior of Tetracaine Hydrochloride in the Presence of Cationic Gemini/Conventional Surfactants

In this approach, tensiometry and UV-visible techniques are used to determine the effect of cationic gemini and conventional surfactants on tetracaine hydrochloride (TCH), an anesthetic drug. We have estimated micellar, interfacial, and energetic constraints. To gain a deep understanding of their mixed association behavior, the outputs were examined using different theoretical models. The critical micelle concentration for single and mixed amphiphiles was estimated. The cmc values of mixed amphiphiles were found between the individual amphiphiles due to strong attractive interaction (synergism) between the components after mixing. The non-ideal behavior of mixtures was confirmed by the larger values of ideal cmc than the experimental cmc values. The negative values of interaction parameter (β) and values of activity coefficients less than unity indicate strong synergistic interaction between drug and surfactant. The stability of the mixed systems is demonstrated by the negative Gibbs free energy of micellization and excess free energy of micellization. In contrast to a single chain surfactant, a double chain surfactant (gemini) exhibits better interactions with the drug. Spectral measurements (UV-visible spectra) were used to monitor the binding of the drug with surfactant (conventional as well as gemini). Studying these mixed aggregates could help to optimize their compositions and find synergistic properties between TCH monomers and surfactants.

A Systematic Review and Meta-Analysis of the Effect of Intraoperative Bupivacaine in Gynaecologic Surgery After 24 Hours or 9 Half-Lives

OBJECTIVE

To review all high quality available evidence regarding the effect of intraoperative bupivacaine 24 hours (or 8.9 half-lives) after intraoperative administration at time of gynaecologic surgery and to ascertain whether a second mechanism of action, beyond the initial prevention of sodium channel depolarization and blockade of nerve impulses, may be occurring.

DATA SOURCES

We searched all major databases with an algorithm designed to include all randomized trials that used any form of local bupivacaine, regardless of dose or route of administration, at the time of any gynaecologic surgery and compared its use with saline placebo.

RESULTS

As expected, we found that bupivacaine showed a significant improvement for all gynaecologic surgeries with respect to pain intensity at 6 hours after surgery when compared with a saline group (mean difference [MD] -1.28; 95% CI -1.96 to -0.61], P = 0.07). We also found a significant difference at 24 hours after surgery, giving evidence to the possibility of a second mechanism of action (MD -0.57; 95% CI -1.10 to -0.05], P = 0.01). Further subgroup analysis for pain levels at 24 hours showed significant decreases in pain for the laparoscopy (MD -0.74; 95% CI -0.93 to -0.54, P < 0.01) and laparotomy (MD -2.60; 95% CI -2.93 to -2.27, P < 0.01)) subgroups but not for the vaginal hysterectomy (MD 0.20; 95% CI -0.69 to 1.09, P = 0.66) or prolapse surgery (MD -0.11; 95% CI -0.41 to 0.19, P = 0.48) subgroups. There was no significant difference with respect to the length of hospital stay (MD -0.11; 95% CI -0.59 to 0.38, P = 0.67).

CONCLUSION

As expected, bupivacaine significantly reduced visual analog pain scores when compared with placebo at 6 hours after surgery, but also showed a significant difference at 24 hours after surgery, giving evidence of a second mechanism of action following the initial sodium channel blockade.

Antimalarial primaquine for skin infiltration analgesia in rats

OBJECTIVES

The purpose of this study was to estimate the ability of antimalarial medications to induce local infiltration analgesia.

METHODS

Using a rat model of skin infiltration anaesthesia, the effects of antimalarial medications (primaquine, chloroquine, hydroxychloroquine and amodiaquine) were compared with the application of lidocaine.

KEY FINDINGS

At a dose of 3 μmol, primaquine and chloroquine displayed better potency (all P < 0.05) and greater duration (all P < 0.01) of cutaneous analgesia than lidocaine, whereas the other antimalarial medications showed a similar potency and duration of cutaneous analgesia when compared with lidocaine. When a dose of 3 μmol antimalarial medication was used, primaquine was the most potent and had the longest duration of action among four antimalarial medications. The relative potency ranking (ED50, 50% effective dose) has been found to be primaquine [2.10 (1.87 - 2.37) μmol] > lidocaine [6.27 (5.32 -7.39) μmol] (P < 0.01). Infiltration analgesia of skin with primaquine had a greater duration of action than did lidocaine on the equipotent (ED25, ED50, ED75) basis (P < 0.01).

CONCLUSIONS

Primaquine and chloroquine have greater potency and longer lasting skin analgesia when compared with lidocaine, while the other antimalarials display a similar potency in comparison with lidocaine.