Synthesis of [1‐8‐NαC]‐zanriorb A1, alanine‐containing analogues, and their cytotoxic and anti‐inflammatory activity

• Published in: Journal of peptide science Vol. 28; no. 8; pp. e3405 - n/a
• Main Authors: Nadeem‐ul‐Haque, Muhammad, Bashir, Anila, Karim, Humira, Khan, Sadiq Noor, Shah, Zafar Ali, Jabeen, Almas, Qayyum, Shaista, Ganesan, A., Choudhary, M. Iqbal, Shaheen, Farzana
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.08.2022
• Subjects: Acetic acid; Alanine; anti‐inflammatory agents; cyclic peptides; Cytotoxicity; Glycine; Herbal medicine; Impurities; Inflammation; Leukemia; Lipopolysaccharides; Lymphocytes; Lymphocytes T; Macrophages; Medicinal plants; Mixtures; Monomethyl-L-arginine; Natural products; Nitric oxide; orbitide[1‐8‐NαC]‐zanriorb A1; orbitides; Peptides; Proline; proline rotamers; Resins; solid‐phase synthesis; Synthesis; Synthetic peptides; cyclic peptides; anti-inflammatory agents; proline rotamers; orbitide[1-8-NαC]-zanriorb A1; solid-phase synthesis; orbitides
• ISSN: 1075-2617; 1099-1387
• DOI: 10.1002/psc.3405

The synthesis of the orbitide[1‐8‐NαC]‐zanriorb A1, isolated from the medicinal plant Zanthoxylum riedelianum, was investigated by solution‐phase macrocyclization of a linear peptide and on‐resin solid‐phase macrocyclization with an acylsulfonamide safety‐catch linker. The solution‐phase route produced a mixture of proline rotamers, and the main component was assigned as the trans, cis rotamer, identical to the natural product. The on‐resin cyclization was less successful, producing mainly a linear peptide, and minor cyclic products as rotameric mixtures. Although the natural product was reported to be significantly cytotoxic against Jurkat leukemia T cells, our synthetic peptides were inactive, suggesting the presence of other rotamers or impurities in the naturally isolated material. Additional analogues of zanriorb A1 were synthesized in which proline and glycine residues were replaced with alanine. While these analogues were not cytotoxic, several of them inhibited the production of nitric oxide in lipopolysaccharide (LPS)‐stimulated macrophages. The most active compound, cyclic[Ala5,6,8]‐zanriorb A1 had an IC50 of 22 μM and was more potent compared with the standard NG‐monomethyl‐l‐arginine acetate (L‐NMMA) with an IC50 of 98 μM, indicating their strong anti‐inflammatory potential. Orbitide[1‐8‐NαC]‐zanriorb A1 was synthesized by solution‐phase macrocyclization of a linear peptide and by on‐resin solid‐phase macrocyclization with an acylsulfonamide safety‐catch linker. The solution‐phase route produced a mixture of proline rotamers, with the main component assigned as the trans, cis rotamer, identical to the natural product. Some of the synthesized alanine‐containing analogues of zanriorb A1 inhibited the production of nitric oxide in lipopolysaccharide‐stimulated macrophages.