Evaluation of the Local Anesthetic Activity, Acute Toxicity, and Structure-Toxicity Relationship in Series of Synthesized 1-Aryltetrahydroisoquinoline Alkaloid Derivatives In Vivo and In Silico.

Isoquinoline alkaloids constitute one of the most common classes of alkaloids that have shown a pronounced role in curing various diseases. Finding ways to reduce the toxicity of these molecules and to increase their therapeutic margin is an urgent matter. Here, a one-step method for the synthesis of a series of 1-aryl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolines was performed in 85-98% yield by the Pictet-Spengler reaction. This was accomplished using the reaction between 3,4-dimethoxyphenylethylamine and substituted benzaldehydes boiling in trifluoroacetic acid. Furthermore, 1-(3'-amino-, 4'-aminophenyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolines were obtained in 94% and 97% yield by reduction in 1-(3'-nitro-, 4'-nitrophenyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolines with SnCl2 × 2H2O. The structures of the substances obtained were confirmed by infrared (IR) and nuclear magnetic resonance (1H and 13C NMR) spectra. ADMET/TOPKAT in silico study concluded that the synthesized compounds exhibited acceptable pharmacodynamic and pharmacokinetic properties without carcinogenic or mutagenic potential but with variable hepatotoxicity. The acute toxicity and structure-toxicity relationship (STR) in the series of 20 derivatives of 1-aryl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolines (3a-r, 4a, b) was studied via determination of acute toxicity and resorptive action in white mice employing intragastric step-by-step administration. The first compound, 1-phenyl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline hydrochloride (3a), showed the highest toxicity with LD50 of 280 mg/kg in contrast to 1-(3'-bromo -4'-hydroxyphenyl)-6,7-methylenedioxy-1,2,3,4-tetrahydroisoquinoline hydrochloride (3e) which proved to be the safest of the compounds studied. Its toxicity was 13.75 times lower than that of the parent compound 3a. All compounds investigated showed high local anesthetic activity on rabbit eyes in the concentrations studied. Only 3r, 3n, and 4a caused eye irritation and redness. All investigated derivatives (except 4b) in 1% concentration were more active than lidocaine, providing longer duration of complete anesthesia. Therefore, based on the obtained results of in silico tests, local anesthesia, and acute toxicity, a conclusion can be drawn that the experimental compounds need further extensive future investigations and possible modifications so that they can act as promising drug candidates.

Discovery of chemical markers for improving the quality and safety control of Sinomenium acutum stem by the simultaneous determination of multiple alkaloids using UHPLC-QQQ-MS/MS.

Sinomenium acutum stem is a popular traditional Chinese medicine used to treat bone and joint diseases. Sinomenine is considered the only chemical marker for the quality control of S. acutum stem in mainstream pharmacopeias. However, higenamine in S. acutum stem is a novel stimulant that was banned by the World Anti-Doping Agency in 2017. Therefore, enhancing the quality and safety control of S. acutum stem to avoid potential safety risks is of utmost importance. In this study, a fast, sensitive, precise, and accurate method for the simultaneous determination of 11 alkaloids in S. acutum stem by ultrahigh-performance liquid chromatography coupled with triple quadrupole tandem mass spectrometry (UHPLC-QQQ-MS/MS) was established. This method successfully analyzed thirty-five batches of S. acutum stem samples. The average contents of sinomenine, magnoflorine, coclaurine, acutumine, higenamine, sinoacutine, palmatine, magnocurarine, columbamine, 8-oxypalmatine, and jatrorrhizine were 24.9 mg/g, 6.35 mg/g, 435 µg/g, 435 µg/g, 288 µg/g, 44.4 µg/g, 22.5 µg/g, 21.1 µg/g, 15.8 µg/g, 9.30 µg/g, and 8.75 µg/g, respectively. Multivariate analysis, including principal component analysis (PCA), orthogonal partial least square method-discriminant analysis (OPLS-DA), and hierarchical cluster analysis (HCA), were performed to characterize the importance and differences among these alkaloids in S. acutum stem samples. As a result, sinomenine, magnoflorine, coclaurine, acutumine, and higenamine are proposed as chemical markers for quality control. Higenamine and coclaurine are also recommended as chemical markers for safety control. This report provides five alkaloids that can be used as chemical markers for improving the quality and safety control of S. acutum stem. It also alerts athletes to avoid the risks associated with consuming S. acutum stem.

A beating heart cell model to predict cardiotoxicity: effects of the dietary supplement ingredients higenamine, phenylethylamine, ephedrine and caffeine.

Some dietary supplements may contain cardiac stimulants and potential cardiotoxins. In vitro studies may identify ingredients of concern. A beating human cardiomyocyte cell line was used to evaluate cellular effects following phenylethylamine (PEA), higenamine, ephedrine or caffeine treatment. PEA and higenamine exposure levels simulated published blood levels in humans or animals after intravenous administration. Ephedrine and caffeine levels approximated published blood levels following human oral intake. At low or midrange levels, each chemical was examined plus or minus 50 µM caffeine, simulating human blood levels reported after consumption of caffeine-enriched dietary supplements. To measure beats per minute (BPM), peak width, etc., rhythmic rise and fall in intracellular calcium levels following 30 min of treatment was examined. Higenamine 31.3 ng/ml or 313 ng/ml significantly increased BPM in an escalating manner. PEA increased BPM at 0.8 and 8 µg/ml, while 80 µg/ml PEA reduced BPM and widened peaks. Ephedrine produced a significant BPM dose response from 0.5 to 5.0 µM. Caffeine increased BPM only at a toxic level of 250 µM. Adding caffeine to PEA or higenamine but not ephedrine further increased BPM. These in vitro results suggest that additional testing may be warranted in vivo to further evaluate these effects.

Construction of drug screening cell model and application to new compounds inhibiting FITC-fibrinogen binding to CHO cells expressing human alphaIIbbeta3.

To identify potential candidates for antiplatelet drugs, human alphaIIbbeta3 (GPIIb/IIIa) was expressed in Chinese hamster ovary (CHO) cells, which was validated by tetrapeptide RGDS (Arg-Gly-Asp-Ser) with IC(50) of 0.057 mM, supported by Basani's results [Basani, R. B., French, D. L., Vilaire, G., Brown, D. L., Chen, F., Coller, B. S., Derrick, J. M., Gartner, T. K., Bennett, J. S., Poncz, M., 2000. A naturally occurring mutation near the amino terminus of alpha IIb defines a new region involved in ligand binding to alpha IIbbeta 3. Blood 95, 180-188]. The ability of 2-(4-substituted-piperazin-1-ylacetyl)-1,2,3,4-tetrahydroisoquinoline derivatives to inhibit fibrinogen binding to alphaIIbbeta3 based on the CHO cell model was measured by flow cytometry using GPIIb/IIIa assay, and the IC(50) values of compounds 1-6 were 0.166, 0.037, 0.311, 0.025, 0.034, and 0.184 mM, respectively. Our research results indicated that the compounds with phenylsulfonyl (compounds 1 and 2) and benzoyl groups (compounds 4 and 5) at position 4 of piperazine showed higher IC(50) values of inhibiting ADP-induced human platelet aggregation. Particularly compound 4 possessed IC(50) value of approximately 6.84 nM. Additionally, a complex model of alphaIIbbeta3 with compound 4 revealed that the pharmacophore of compound 4, including m-nitro group of 4-benzene-piperazine, the nitrogen atom in the piperazine group, and 2-nitrogen of 1,2,3,4-tetrahydroisoquinoline nucleus, interacted with the hydroxyl groups of Thr125 of beta3 and Tyr166 of alpha2b by hydrogen bonds and the carboxyl group at side chain of Asp179 of alpha2b in the fashion of electrostatic interaction. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assays showed that compounds 4 and 5 possess potential anti-cancer activities, suggesting a potential role of integrin-guided signal pathway in cancer therapy. Further evaluation is under investigation.