Excavating Precursors from the Traditional Chinese Pair Herbs Polygala tenuifolia and Gastrodia elata: Synthesis, Anticonvulsant Activity Evaluation of 3,4,5-Trimethoxycinnamic Acid (TMCA) Peptide Analogs

Background: Epilepsy comprises a range of disorders affecting the central nervous system (CNS) characterized by recurrent seizures, impacting approximately 60 million individuals globally. In this study, we designed and derived a series of peptide analogs 1–30 of 3,4,5-trimethoxycinnamic acid (TMCA) from the herbal combinations of Polygala tenuifolia and Gastrodia elata, recognized in Traditional Chinese Medicine (TCM). Methods: All the analogs were synthesized, and their anticonvulsant efficacy was subsequently assessed. The anticonvulsant activity of all TMCA analogs was evaluated using two acute seizure models in mice: the maximal electroshock (MES) and the sc-pentylenetetrazole (PTZ) models. Furthermore, we explored the electroencephalogram (EEG) and double-labeling immunofluorescence experiments were carried out as well. Results: Our findings indicated that compounds 11, 19, 22, and 23 demonstrated favorable anticonvulsant activities during the initial assessment. Compounds 19 and 23 also played roles in controlling the onset of epilepsy in EEG, modulating levels of GABA aminotransferase (GABA-AT)/gamma-aminobutyric acid type A receptor (GABAAR), interacting with active sites of GABA-AT and GABAAR obtained from docking simulation methods. Conclusions: Novel derivatives in this study provide new cores for further design and optimization inspired by TCM herb pair drugs P. tenuifolia and G. elata, with the aim of exploring new anticonvulsant agents.