Syntheses of tetrahydroisoquinoline derivatives that inhibit NO production in activated BV-2 microglial cells

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.

Possible involvement of tetrahydrobiopterin in the disturbance of redox homeostasis in sepsis - Induced brain dysfunction

BACKGROUND AND AIM

Tetrahydrobiopterin (BH4) is an essential co-factor that regulates nitric oxide (NO) and reactive oxygen species (ROS) production by nitric oxide synthases (NOS). In this study, we evaluated the effects of sepsis on BH4 level and redox status in the brain by using the rat model of sepsis-induced by cecal ligation and puncture (CLP) and examined whether BH4 and/or acetyl-L-carnitine (ALC) could prevent the neuronal apoptosis and neurological changes induced by sepsis.

MATERIAL AND METHOD

Male albino rats were randomly and blindly divided into 8 groups: sham, sham + BH4, sham + ALC, sham +BH4+ ALC, CLP, CLP + BH4, CLP + ALC, and CLP+BH4+ ALC. We measured neurological indicators, brain levels of BH4, guanosine triphosphate cyclohydrolase (GTPCH), sepiapterin reductase (SR) and dihydropteridine reductase (DHPR) genes expression (Essential enzymes in BH4 biosynthesis and recycling pathways). We investigated also brain redox status and both endothelial and inducible NOS expressions.

RESULTS

Brain of septic rats demonstrated a reduced BH4 bioavailability, downregulation of BH4 synthetic enzymes, increased production of hydrogen peroxide and impaired antioxidant enzymes activities. Treatments with BH4 and/or ALC increased BH4 level, upregulated BH4 synthetic enzymes expressions, and attenuated oxidative-induced neuronal apoptosis.

CONCLUSION

Our results suggest that BH4 and/or ALC might protect the brain against oxidative stress induced neuronal apoptosis by restoring bioavailability of BH4 and upregulating of BH4 synthetic enzymes in the brain during sepsis.

Substituted tetrahydroisoquinolines: synthesis, characterization, antitumor activity and other biological properties

This work deals with the molecular design, synthesis and biological activity of a series of tetrahydro[1,4]dioxanisoquinolines and dimethoxyisoquinoline analogues. This study describes the synthesis strategy of these potential antitumor compounds, their multi-step synthesis and their optimization. A series of tetrahydroisoquinolines was synthesized and their cytotoxicity evaluated. Some of these tetrahydroisoquinolines showed promising KRas inhibition, antiangiogenesis activity and antiosteoporosis properties. Molecular modeling studies showed that compound 12 bind in the p1 pocket of the KRas protein making interactions with the hydrophobic residues Leu56, Tyr64, Tyr71 and Thr74 and hydrogen bonds with residues Glu37 and Asp38.

Synthesis and biological evaluation of isoindoloisoquinolinone, pyroloisoquinolinone and benzoquinazolinone derivatives as poly(ADP-ribose) polymerase-1 inhibitors

A series of novel fused isoquinolinones with isoindoloisoquinolinone, pyroloisoquinolinone, and benzoquinalizinone skeletons were synthesized from corresponding phenethylimides. The isoquinolinone derivatives were evaluated for their protective effect on chicken erythrocytes subjected to oxidative damage. The effect of isoquinolinone derivatives were analysed by estimation of cell viability, antioxidant enzyme activities, DNA damage (comet assay), PARP-1 inhibition assay and molecular docking of the compounds with PARP-1 active site. The compounds CRR-271, CRR-288 and CRR-224+225 showed significant protective effect at 100 μM concentration. The PARP-1 inhibition assay revealed the IC50 values of CRR-271, CRR-288 and CRR-224+225 as <200 nM, further molecular docking studies shows higher binding energies with PARP-1 active site. Interesting findings in this study suggest that the novel isoquinolinone derivatives inhibit PARP-1 activity and protect cells against oxidative DNA damage, which could be implemented in the treatment of inflammatory diseases.

A novel compound PTIQ protects the nigral dopaminergic neurones in an animal model of Parkinson's disease induced by MPTP

BACKGROUND AND PURPOSE

In Parkinson's disease, the dopaminergic neurones in the substantia nigra undergo degeneration. While the exact mechanism for the degeneration is not completely understood, neuronal apoptosis and neuroinflammation are thought to be key contributors. We have recently established that MMP-3 plays crucial roles in dopaminergic cell death and microglial activation.

EXPERIMENTAL APPROACH

We tested the effects of 7-hydroxy-6-methoxy-2-propionyl-1,2,3,4-tetrahydroisoquinoline (PTIQ) on expression of MMP-3 and inflammatory molecules and dopaminergic cell death in vitro and in an animal model of Parkinson's disease, and Parkinson's disease-related motor deficits. The pharmacokinetic profile of PTIQ was also evaluated.

KEY RESULTS

PTIQ effectively suppressed the production of MMP-3 induced in response to cellular stress in the dopaminergic CATH.a cell line and prevented the resulting cell death. In BV-2 microglial cells activated with lipopolysaccharide, PTIQ down-regulated expression of MMP-3 along with IL-1β, TNF-α and cyclooxygenase-2 and blocked nuclear translocation of NF-κB. In the mouse model of Parkinson's disease ,induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), PTIQ attenuated the associated motor deficits, prevented neurodegeneration and suppressed microglial activation in the substantia nigra. Pharmacokinetic analysis showed it was relatively stable against liver microsomal enzymes, did not inhibit the cytochrome p450 isozymes or the hERG ion channel, exhibited no cytotoxicity on liver cells or lethality when administered at 1000 mg kg(-1) and entered the brain rather rapidly yielding a 28% brain:plasma ratio after i.p. injection.

CONCLUSIONS AND IMPLICATIONS

These results suggest PTIQ has potential as a candidate drug for disease-modifying therapy for Parkinson's disease.

Bio-inspired synthesis and biological evaluation of a colchicine-related compound library

A bio-inspired investigation of the reactions of substrates of type 1 with VOF(3) and PIFA [phenyliodine(III) bis(trifluoroacetate)] led to a collection of colchicine-like compounds 2-5 and related systems. Biological evaluation revealed that some of the synthesized products had significant cytotoxic properties against the colon cancer cell line HT-29.

Biocatalytic organic synthesis of optically pure (S)-scoulerine and berbine and benzylisoquinoline alkaloids

A chemoenzymatic approach for the asymmetric total synthesis of the title compounds is described that employs an enantioselective oxidative C-C bond formation catalyzed by berberine bridge enzyme (BBE) in the asymmetric key step. This unique reaction yielded enantiomerically pure (R)-benzylisoquinoline derivatives and (S)-berbines such as the natural product (S)-scoulerine, a sedative and muscle relaxing agent. The racemic substrates rac-1 required for the biotransformation were prepared in 4-8 linear steps using either a Bischler-Napieralski cyclization or a C1-Cα alkylation approach. The chemoenzymatic synthesis was applied to the preparation of fourteen enantiomerically pure alkaloids, including the natural products (S)-scoulerine and (R)-reticuline, and gave overall yields of up to 20% over 5-9 linear steps.