Facile synthesis and in vitro properties of 1-alkyl- and 1-alkyl-N-propargyl-1,2,3,4-tetrahydroisoquinoline derivatives on PC12 cells

Visible light as a sole requirement for alkylation of α-C(sp3)-H of N-aryltetrahydroisoquinolines with alkylboronic acids

An alkylation of α-C(sp3)-H at N-aryltetrahydroisoquinolines with alkylboronic acids was developed under visible-light irradiation in the absence of additional photocatalyst. The reaction proceeded well, tolerating a variety of functional groups, and featured low-cost and mild reaction conditions. A preliminary mechanistic study indicated that an electron donor-acceptor (EDA) complex between an electron-rich N-aryltetrahydroisoquinoline and an electron-poor alkylboronic acid was involved in the reaction.

Preventative effects of 1-methyl-1,2,3,4-tetrahydroisoquinoline derivatives (N-functional group loading) on MPTP-induced parkinsonism in mice

1,2,3,4-Tetrahydroisoquinoline (TIQ) is endogenously present in human brain, and some of its derivatives are thought to contribute to the induction of Parkinson's disease (PD)-like signs in rodents and primates. In contrast, the endogenous TIQ derivative 1-methyl-TIQ (1-MeTIQ) is reported to be neuroprotective. In the present study, we compared the effects of artificially modified 1-MeTIQ derivatives (loading an N-propyl, N-propenyl, N-propargyl, or N-butynyl group) on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD-like signs in mice. In a behavioral study, MPTP-induced bradykinesia was significantly decreased by all compounds. However, only 1-Me-N-propargyl-TIQ showed an inhibitory effect by blocking the MPTP-induced reduction in striatal dopamine content and the number of nigral tyrosine hydroxylase-positive cells. Western blot analysis showed that 1-Me-N-propargyl-TIQ and 1-Me-N-butynyl-TIQ potently prevented the MPTP-induced decrease in dopamine transporter expression, whereas 1-MeTIQ and 1-Me-N-propyl-TIQ did not. These results suggest that although loading an N-propargyl group on 1-MeTIQ clearly enhanced neuroprotective effects, other N-functional groups showed distinct pharmacological properties characteristic of their functional groups. Thus, the number of bonds and length of the N-functional group may contribute to the observed differences in effect.

Design, synthesis, neuroprotective, antibacterial activities and docking studies of novel thieno[2,3-d]pyrimidine-alkyne Mannich base and oxadiazole hybrids

A series of thieno[2,3-d]pyrimidine alkyne Mannich base derivatives (7a-e, 8a-e) and thieno[2,3-d]pyrimidine 1,3,4-oxadiazole derivatives (9a-e, 10a-e) have been synthesized and evaluated for their neuroprotective and neurotoxicity activities where 9a, 10d displayed good neuroprotection 10.6 and 11.88 µg/mL respectively against the H₂O₂ induced cell death at the EC₅₀ values and 9b, 9d showed respective toxic effects on PC12 cells at CC₅₀ 86.12 and 94.16 µg/mL. Compounds 9a, 9e, 10a and 10b showed strong antibacterial activity against two gram positive (S. aureus, B. subtilis) and two gram-negative strains (E. coli, P. aeruginosa) and showed good binding affinities with C(30) carotenoid dehydrosqualene synthase, Gyrase A and LpxC. This is the first report for the demonstration of thieno[2,3-d] pyrimidine derivatives as promising neuroprotective agents against H₂O₂ induced neurotoxicity on PC12 cells.

Properties of 3-methyl-TIQ and 3-methyl-N-propargyl-TIQ for preventing MPTP-induced parkinsonism-like symptoms in mice

BACKGROUND

Selegiline, a therapeutic drug for Parkinson's disease (PD), structurally resembles the endogenous parkinsonism-related compound 1,2,3,4-tetrahydroisoquinoline (TIQ). In the present study, we evaluated the effects of 3-methyl-TIQ (3-MeTIQ) and 3-methyl-N-propargyl-TIQ (3-Me-N-proTIQ), selegiline mimetic TIQ derivatives, for preventing 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonism-like symptoms in mice.

METHODS

We evaluated the preventative effects of 3-MeTIQ and 3-Me-N-proTIQ on MPTP-induced bradykinesia and depletion of striatal dopamine (DA) and nigral tyrosine hydroxylase (TH)-positive cells.

RESULTS

MPTP-induced bradykinesia was not different when mice were pretreated with 3-MeTIQ, except for the high-dose group. However, pretreatment with 3-Me-N-proTIQ significantly prevented the appearance of this akinesic status. MPTP-induced striatal DA and 3,4-dehydroxyphenylacetic acid reduction were significantly prevented by pretreatment with 3-Me-N-proTIQ, but not 3-MeTIQ, in a dose-dependent manner. On the other hand, levels of serotonin and its metabolite, 5-hydroxyindole acetic acid, in the striatum were increased following treatment with 3-MeTIQ. In addition, the MPTP-induced decrease in TH-positive cells in the substantia nigra was significantly reduced by pretreatment with 3-Me-N-proTIQ, but not 3-MeTIQ.

CONCLUSIONS

These results suggest that not only does 3-Me-N-proTIQ have potential as a candidate compound for disease-modifying therapy for PD, but also the N-propargyl functional group plays an important role in neuroprotection.

Preventative effects of 1,3-dimethyl- and 1,3-dimethyl-N-propargyl-1,2,3,4-tetrahydroisoquinoline on MPTP-induced Parkinson's disease-like symptoms in mice

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is well known as an exogenous dopaminergic neurotoxin that induces Parkinson's disease-like symptoms. In addition, 1,2,3,4-tetrahydroisoquinoline (TIQ) derivatives have been investigated as endogenous MPTP mimetic compounds that structurally resemble selegiline, a commercially available drug for treating Parkinson's disease. In the present study, we examined the ability of 1,3-dimethyl-TIQ (1,3-diMeTIQ) and 1,3-dimethyl-N-propargyl-TIQ (1,3-diMe-N-proTIQ) to prevent MPTP-induced Parkinson's disease-like symptoms in mice and to prevent 1-methyl-4-phenylpyridinium ion (MPP+, an active metabolite of MPTP)-induced cytotoxicity in vitro, including its structural stereoselectivity. Repeated administration of MPTP induced bradykinesia, a symptom of behavioral abnormality; this was prevented by both 1,3-diMeTIQ and 1,3-diMe-N-proTIQ pretreatments. Pretreatment with 1,3-diMeTIQ did not prevent the MPTP-induced decrease in dopamine content in the striatum or the decrease in the number of tyrosine hydroxylase-positive cells in the substantia nigra. On the other hand, 1,3-diMe-N-proTIQ prevented these Parkinson's disease-like symptoms; in particular, the trans-isomer of this agent showed potent protective effects. However, the ability of the trans-1,3-diMe-N-proTIQ isomer to prevent MPP+-induced PC12 cell death was weaker than that of its cis-isomer. Thus, stereoisomers of 1,3-diMe-N-proTIQ exhibit different effects; cis-1,3-diMe-N-proTIQ inhibits MPP+-induced cytotoxicity while trans-1,3-diMe-N-proTIQ exhibits neuroprotective effects primarily through MPTP-related biological events in mice. These results also indicate the possibility of utilizing, at least in part, the stereoselective efficacy of 1,3-diMe-N-proTIQ against MPTP and/or MPP+-induced adverse states.