The emergence of diverse peptide derivatives has been due to constant efforts to find a specific peptide with pronounced biological activity for effective application as a therapeutic. Spinorphin-peptide products have been reported to possess various applications and properties. In the present study, spinorphin peptides with a rhodamine residue and a modification in the amino acid backbone were synthesized by a solid-phase method using Fmoc chemistry. The results obtained from the spectral and electrochemical techniques used: Scanning electron microscopy (SEM), UV-vis, fluorescence, infrared spectroscopy (IR), and voltammetry were used to elucidate the structural characteristics and some physicochemical properties to gain insight into their behavior in the solid state and in aqueous solutions with different pHs. Both Rh-S5 and Rh-S6 had compound anticonvulsant effect comparable to Rh-S against psychomotor seizures at the highest dose of 20 μg. Furthermore, Rh-S6 showed a strong ability to inhibit seizure propagation and had a similar threshold to Rh-S against the intravenous pentylenetetrazol induced clonic seizure in mice; one of the three hybrid spinorphin analogs tested when screened for anticonvulsant activity. Biological tests against several bacterial pathogens such as Staphylococcus aureus, Escherichia coli, and Bacillus cereus showed similar results to negative control of the new peptide derivatives. The compounds also showed weak activity against Candida albicans fungus. The antioxidant testing results revealed more than 50% activity by reviewing the radical deterrence capabilities of 2,2-diphenyl-1-picrylhydrazyl (DPPH). The results are indicative of the ongoing search for universal antimicrobial agents with pronounced synergism when used simultaneously as anticonvulsant, antibacterial, and antifungal agents.
Keywords: anticonvulsant activity; biological activity; electrochemistry; fluorimetry; rhodamine peptides; spinorphin analogs.