Mar. Drugs 2019, 17, 430
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monoamine transmitters is considered to be a fundamental neurochemical feature in patients with
depression. Hence, patients could be treated by increasing monoamine concentrations in the CNS [23].
We found that 2c and 2d increased concentrations of serotonin and norepinephrine markedly without
altering dopamine concentrations in mouse brains, in a similar manner to that seen with the positive
control fluoxetine in the FST. A cure for patients with major depression is deemed to include an increase
in levels of serotonin or norepinephrine [24,25]. Thus, the antidepressant activities of 2c and 2d could
be reflected by measuring levels of serotonin and norepinephrine in the CNS.
4
. Method and Material
4
.1. Reagents and Instruments
Positive drug: fluoxetine (purity > 99%) was purchased from Sigma. Melting points were measured
by the melting point apparatus (WRS-1B, Shanghai, China). Infrared spectra (IR in KBr) were recorded
1
13
using FT-IR1730 (Bruker, Switzerland). H and C NMR spectra were recorded on an AV-300 (Bruker,
Switzerland), and the chemical shift values are in ppm relative to the TMS or solvent peaks. Mass spectra
were recorded on MALDI-TOF/TOF mass spectrometer (Bruker Daltonik, Bremen, Germany). Main
reagents were purchased from Aldrich Chemical Corporation (Shanghai, China).
4
.2. Synthesis of Benzo[d]thiazol and Benzyloxybenzo[d]thiazole Derivatives 2a–2i, 3a–3r
A solution of benzo[d]thiazol-2-ol (3.0 mmol), anhydrous K CO (3.0 mmol) and 5 mL DMF was
2
3
◦
stirred in a round-bottomed flask for 1 h at 60 C, then, 1.2 mmol of alkyl bromide or substituted
brominated benzyl compound was added slowly to the reaction solution. The reaction solution was
refluxed for 5 h, the reaction was monitored by TLC. DMF was evaporated under reduced pressure,
the residue was washed with water, filtered, dried and the crude product was crystallized from MeOH.
The yield, melting point, and spectral data of each compound are given below.
4
.3. Synthesis of Ethoxylbenzo[d]thiazole Derivatives 4a–4g
A mixture of benzo[d]thiazol-2-ol (3.0 mmol, 0.5 g), 1,2-dibromoethane (3.0 mmol, 0.6 g) and
anhydrous K CO (3.0 mmol, 0.4 g) was refluxed in DMF for 1 h, after the completion of the reaction
2
3
(
as monitored by TLC), DMF was evaporated and the precipitated product was washed with deionized
water, dried. Then, 2-(2-bromoethoxy)benzo[d]thiazole (3.0 mmol, 0.8 g), 10 mL of a mixture of NaOH
and substituted phenol was refluxed in EtOH for 2–5 h. After the completion of the reaction (as
monitored by TLC), the solution was filtered and washed with 10% HCl and water. The crude product
was recrystallized from MeOH. The melting points, yields, and spectral data of 4a–4g are given below.
4
.4. Experimental Animal and Compounds Treatment
Male ICR mice (20 2 g) were purchased from the laboratory of animal study of Zhejiang Academy
±
of medical sciences. Before the experiment started, mice were tamed for 1 week. During and before the
test, mice were kept at 23
◦
±
2 C for 12 h, at day and night circle, and tap water and standard food
granules were provided. The procedures were adopted according to the National Institute of Health
Guide for the Care and Use of Laboratory Animals and approved by the Ethics Committee of our
Institution in this study. All the test compounds were dissolved in PEG-400 (polyethylene glycol-400).
Other drugs were dissolved in 0.9% NaCl (isotonic saline solution). Fluoxetine, phenobarbital, and
valproate were used as positive controls and the vehicle as the negative control. All the test compounds
and other drugs were administered intraperitoneally for 30 min in the FST, the volume of the drug
solution and vehicle was 0.1 mL/20 g of mice.
4
.5. In the FST
Male ICR mice were randomized into groups. On the day of the experiment, mice were placed
one at a time into a Perspex barrel (elevation 20 cm, 10 cm diameter) including 10 cm water about