Synthesis, Anticonvulsant and Antinociceptive Activity of New Hybrid Compounds: Derivatives of 3-(3-Methylthiophen-2-yl)-pyrrolidine-2,5-dione

Abstract

The present study aimed to design and synthesize a new series of hybrid compounds with pyrrolidine-2,5-dione and thiophene rings in the structure as potential anticonvulsant and antinociceptive agents. For this purpose, we obtained a series of new compounds and evaluated their anticonvulsant activity in animal models of epilepsy (maximal electroshock (MES), psychomotor (6 Hz), and subcutaneous pentylenetetrazole (scPTZ) seizure tests). To determine the mechanism of action of the most active anticonvulsant compounds (3, 4, 6, 9), their influence on the voltage-gated sodium and calcium channels as well as GABA transporter (GAT) was assessed. The most promising compound 3-(3-methylthiophen-2-yl)-1-(3-morpholinopropyl)pyrrolidine-2,5-dione hydrochloride (4) showed higher ED₅₀ value than those of the reference drugs: valproic acid (VPA) and ethosuximide (ETX) (62.14 mg/kg vs. 252.7 mg/kg (VPA) in the MES test, and 75.59 mg/kg vs. 130.6 mg/kg (VPA) and 221.7 mg/kg (ETX) in the 6 Hz test, respectively). Moreover, in vitro studies of compound 4 showed moderate but balanced inhibition of the neuronal voltage-sensitive sodium (site 2) and L-type calcium channels. Additionally, the antinociceptive activity of the most active compounds (3, 4, 6, 9) was also evaluated in the hot plate test and writhing tests, and their hepatotoxic properties in HepG2 cells were also investigated. To determine the possible mechanism of the analgesic effect of compounds 3, 6, and 9, the affinity for the TRPV1 receptor was investigated.

Keywords: anticonvulsant; antinociceptive; pirrolidyne-2,5-dione; thiophene.

Figure 1

Proposed structural modifications and active compounds obtained in the previous studies [14,15].

Scheme 1

Synthetic route of the target compounds 3–17.

Figure 2

Anticonvulsant activity of compounds 3, 4, 14, 17, and ethosuximide (ETX) in the scPTZ test. Each value represents the mean ± S.E.M. obtained from 4–6 mice. Statistical analysis: one-way analysis of variance (ANOVA), followed by Dunnett’s post hoc test. Significant difference compared to the control group: ** p < 0.01, *** p < 0.001. Data for ETX from the previous study [24].

Figure 3

Antinociceptive activity of compounds 3, 4, 6, 9 and acetylsalicylic acid (30, 50, and 100 mg/kg) in the acetic acid-induced writhing test. Data are presented as mean ± SEM and were analyzed by one-way analysis of variance (ANOVA), followed by Dunnett’s post hoc test or t-test. Significant difference compared to the vehicle-treated group. * p < 0.05, ** p < 0.01, *** p < 0.001, n = 8.

Figure 4

Effects of compounds 3, 4, 6, 9 at the dose of 30 mg/kg, ip, and morphine (5 mg/kg) on response latency in the hot plate test in mice. Data are presented as mean ± SEM and were analyzed by one-way analysis of variance, followed by Dunnett’s post hoc test or t-test. Significant difference compared to the vehicle-treated group—* p < 0.05, *** p < 0.001; n = 8.

Figure 5

Viability of HepG2 cells incubated in the presence of compounds 3, 4, 6, 9 and astemizole at concentration range 1–100 µM for 24 h. The graph show results from PrestoBlue assay expressed as the percentage of control condition ± SEM. Three independent experiments were performed.