RESEARCH ARTICLE Anticonvulsant evaluation and docking analysis of VV-Hemorphin-5 analogues Petar Todorov 1 | Miroslav Rangelov 2 | Petia Peneva 1 | Nadezhda Todorova 3 | Jana Tchekalarova 4 Enabling Technologies Strategy, Management & Health Policy Hit, Lead & Candidate Discovery Preclinical Research & Development Clinical Research Post-Market Research 1 Department of Organic Chemistry, University of Chemical Technology and Metallurgy, Sofia, Bulgaria 2 Laboratory Chemistry and Biophysics of Proteins and Enzymes, Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Sofia, Bulgaria 3 Department of Ecosystem Research, Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, Sofia, Bulgaria 4 Department of Behavioral Neurobiology, Institute of Neurobiology, Bulgarian Academy of Sciences, Sofia, Bulgaria Correspondence Jana Tchekalarova, Institute of Neurobiology, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria. Emails: janetchekalarova@gmail.com; jane@bio.bas.bg Funding information The Scientific Research Centre at UCTM, Grant/Award Number: 11813/2018 Abstract VV-Hemorphin-5 is an endogenous opioid peptide of the Hemorphin family with affinity at opioid receptors. A series of C-amide analogues have been synthesized, based on the structure of VV-Hemorphin-5, modified at position 1 and 7 by the un/natural amino acids (Aa8-Val-Val-Tyr-Pro-Trp-Thr-Gln-NH 2 and Val-Val-Tyr-Pro-Trp-Thr-Aa1-NH 2 ) using SPPS, Fmoc-chemistry. The peptide derivatives were evaluated for their anticonvulsant activity in three acute seizure tests in male ICR mice, the maximal electroshock (MES), the 6 Hz psy- chomotor seizure test, and the timed intravenous pentylenetetrazole (ivPTZ) infusion test. Their neurotoxicity was assessed in the rotarod test. Among the tested peptide analogues, V4 showed anticonvulsant activity in the three seizure tests that was comparable to the VV-Hemorphin-5 (V1) used as a positive control. While V5, V6, and V7 peptide derivatives exhibited anticonvulsant activity in the MES and 6 Hz test, they were inactive (V7) or showed pro-convulsant effect (V5 and V6) in the i.v. PTZ test. At a dose of 10 μg/mouse the peptide V2 was effective against clonic seizures induced by PTZ. Motor coordination was not affected by newly developed analogues of VV-Hemorphin-5. Docking study results sug- gest that kappa opioid receptor binding could be the mechanism of action of peptide deriva- tives with anticonvulsant activity. The results suggest that incorporation of nonproteinogenic and/or natural amino acids at position 1 and 7 of the VV-Hemorphin-5 scaffold deserve further evaluation in models of epilepsy and derivatization. KEYWORDS anticonvulsant activity, docking, Hemorphin analogues, mice, SPPS 1 | INTRODUCTION Epilepsy, considered a chronic neurological disease, is characterized by seizures that are caused by a loss of balance between classical excitatory glutamatergic and inhibitory gama amino acid (GABA) neu- rotransmitter system (Meldrum, 2002). Epileptic seizures might be lim- ited to a part of the brain or to propagate to other areas or to generalize the entire brain as a result of synchronous and excessive electrical discharges in a particular group of neurons (Fisher et al., 2014). The therapy of epilepsy is mostly symptomatic to control seizure activity through antiepileptic drugs (AEDs). However, about 30% of the patients remain refractory to pharmacological treatments (Laxer et al., 2014). Alternative approaches involve vagus stimulation or surgical hippocampal resection (Morris & Mueller, 1999; Ryvlin & Rheims, 2008). In addition, most of the current AEDs have serious side effects including exacerbation of the comorbid depression, ataxia, headache, etc. (Perucca & Gilliam, 2012). The endogenous neuropep- tide signaling, including dynorphin, neuropeptide Y, galanin, active Received: 4 December 2018 Revised: 6 January 2019 Accepted: 8 January 2019 DOI: 10.1002/ddr.21514 Drug Dev Res. 2019;1–13. wileyonlinelibrary.com/journal/ddr © 2019 Wiley Periodicals, Inc. 1