Bioassay guided fractionation of the EtOAc fraction of the sponge Callyspongia aerizusa yielded seven new cytotoxic cyclic peptides callyaerins A-F (1-6) and H (8). Their structures were determined using extensive 1D ( H, C and DEPT) and 2D (COSY, HMQC, HMBC, TOCSY, and ROESY) NMR and mass spectral (ESI and HRESI-TOF) data. All compounds were cyclic peptides containing ring systems of 5-9 amino acids and side chains of 2-5 amino acids in length. An unusual (Z)-2,3-diaminoacrylic acid unit provided the template for ring closure and afforded the linkage to the peptidic side chain which was always initiated with a proline moiety. All peptides contained three or more proline residues and the remaining residues were predominantly hydrophobic residues with all amino acids present in the l form. Callyaerins A-F (1-6) and H (8) showed biological activity in antibacterial assays and in various cytotoxicity assays employing different tumour cell-lines (L5178Y, HeLa, and PC12). Callyaerins E (5) and H (8) exhibited strong activity against the L5178Y cell line with ED values of 0.39 and 0.48 µM, respectively. On the other hand, callyaerin A (1) showed strong inhibitory properties towards C. albicans.
- Callyspongia aerizusa
- Proline-rich cyclic peptides
Ibrahim, S. R. M., Min, C. C., Teuscher, F., Ebel, R., Kakoschke, C., Lin, W., Wray, V., Edrada-Ebel, R., & Proksch, P. (2010). Callyaerins A-F and H, new cytotoxic cyclic peptides from the Indonesian marine sponge Callyspongia aerizusa. Bioorganic & Medicinal Chemistry, 18(14), 4947-4956. https://doi.org/10.1016/j.bmc.2010.06.012