First total synthesis and biological screening of a proline-rich cyclopeptide from a caribbean marine sponge

A natural heptacyclopeptide, stylissamide G (7), previously isolated from the Bahamian marine sponge Stylissa caribica from the Caribbean Sea, was synthesized via coupling of the tetrapeptide L-phenylalanyl-L-prolyl-L-phenylalanyl-L-proline methyl ester with the tripeptide Boc-L-leucyl-L-isoleucyl-L-proline, followed by cyclization of the linear heptapeptide fragment. The structure of the synthesized cyclooligopeptide was confirmed using quantitative elemental analysis, FT-IR, 1H NMR, 13C NMR and mass spectrometry. Results of pharmacological activity studies indicated that the newly synthesized cycloheptapeptide displayed good anthelmintic potential against Megascoplex konkanensis, Pontoscotex corethruses and Eudrilus eugeniea at 2 mg/mL and in addition, potent antifungal activity against pathogenic Candida albicans and dermatophytes Trichophyton mentagrophytes and Microsporum audouinii at a concentration of 6μg/mL.