Analgesic and antiallodynic activity of novel anticonvulsant agents derived from 3-benzhydryl-pyrrolidine-2,5-dione in mouse models of nociceptive and neuropathic pain

Comparison of analgesic activities of aconitine in different mice pain models

Aconitine (AC) is the primary bioactive and secondary metabolite alkaloidin of Aconitum species which is accounted for more than 60% of the total diester-diterpenoid alkaloids in Aconite. To evaluate the analgesic effects of AC, 4 different pain models including hot plate assay, acetic acid writhing assay, formalin and CFA induced pain models were adopted in this study. In hot plate experiment, AC treatment at concentration of 0.3 mg/kg and 0.9 mg/kg improved the pain thresholds of mice similar to the positive drug aspirin at the concentration of 200 mg/kg (17.12% and 20.27% VS 19.21%). In acetic acid writhing experiment, AC significantly reduced the number of mice writhing events caused by acetic acid, and the inhibition rates were 68% and 76%. These results demonstrated that AC treatment revealed significant analgesic effects in both acute thermal stimulus pain model and chemically-induced visceral pain model. The biphasic nociceptive responses induced by formalin were significantly inhibited after AC treatment for 1h or 2h. The inhibition rates were 33.23% and 20.25% of AC treatment for 1h at 0.3 mg/kg and 0.9 mg/kg in phase I. In phase II, the inhibition rates of AC and aspirin were 36.08%, 32.48% and 48.82% respectively, which means AC showed similar analgesic effect to non-steroidal anti-inflammatory compounds. In the chronic CFA-induced nociception model, AC treatment also improved mice pain threshold to 131.33% at 0.3 mg/kg, which was similar to aspirin group (152.03%). Above all, our results verified that AC had obviously analgesic effects in different mice pain models.

Design, Synthesis and Biological Activity of New Amides Derived from 3-Benzhydryl and 3-sec-Butyl-2,5-dioxo-pyrrolidin-1-yl-acetic Acid

The aim of this study was to design and synthesize two new series of pyrrolidine-2,5-dione-acetamides with a benzhydryl or sec-butyl group at position 3 as potential anticonvulsants. Their anticonvulsant activity was evaluated in standard animal models of epilepsy: the maximal electroshock (MES), the 6 Hz, and the subcutaneous pentylenetetrazole (scPTZ) tests. The in vivo studies revealed the most potent anticonvulsant activity for 15 (3-(sec-butyl)-1-(2-(4-(3-trifluoromethylphenyl)piperazin-1-yl)-2-oxoethyl)pyrrolidine-2,5-dione), with ED₅₀ values of 80.38 mg/kg (MES) and 108.80 mg/kg (6 Hz). The plausible mechanism of action was assessed in in vitro binding assays, in which 15 interacted effectively with voltage-gated sodium (site 2) and L-type calcium channels at a concentration of 100 μM. Subsequently, the antinociceptive activity of compounds 7 and 15 was observed in the hot plate test of acute pain. Moreover, compounds 7, 11 and 15 demonstrated an analgesic effect in the formalin test of tonic pain. The hepatotoxic properties of the most effective compounds (7, 11 and 15) in HepG2 cells were also investigated.

Research progress in biological activities of succinimide derivatives

Succinimides are well recognized heterocyclic compounds in drug discovery which produce diverse therapeutically related applications in pharmacological practices. Researches in medicinal chemistry field have isolated and synthesized succinimide derivatives with multiple medicinal properties including anticonvulsant, anti-inflammatory, antitumor and antimicrobial agents, 5-HT receptor ligands and enzyme inhibitors. Simultaneously, SAR (Structure-Activity Relationship) analysis has been gradually possessed, along with a great deal of derivatives have been derived for potential targets. In this article, we comprehensively summarize the biological activities and SAR for succinimide derivatives, along with the featuring bioactive molecules reported in patents, wishing to provide an overall retrospect and prospect on the succinimide analogues.

Synthesis, anticonvulsant, and antinociceptive activity of new 3-(3-methyl-2,5-dioxo-3-phenylpyrrolidin-1-yl)propanamides and 3-phenyl-butanamides

A focused library of new 3-(3-methyl-2,5-dioxo-3-phenylpyrrolidin-1-yl)propanamides and their nonimide analogs were synthesized and tested for anticonvulsant activity. These compounds were obtained through the coupling reaction of the starting carboxylic acids with appropriate amines. The initial anticonvulsant screening was performed in mice (intraperitoneal administration) using the maximal electroshock seizure (MES) and the subcutaneous pentylenetetrazole (scPTZ) seizure models. The most promising compound 6 showed more potent protection in the MES and scPTZ tests than valproic acid, which is still recognized as one of the most relevant first-line anticonvulsants. The structure-activity relationship analysis revealed that the presence of the pyrrolidine-2,5-dione ring is important but not indispensable to retain anticonvulsant activity. Additionally, compound 6 showed potent antinociceptive properties in the oxaliplatin-induced neuropathic pain model in mice. The most plausible mechanism of action for compound 6 may result from its influence on the neuronal sodium channel (Site 2) and the high-voltage-activated L-type calcium channel.