Synthesis, Characterization, and Biological Activity Studies on Fanlizhicyclopeptide A

The synthesis of a proline-rich cyclic heptapeptide, fanlizhicyclopeptide A (8), previously isolated from the fruits of Annona squamosa (sugar-apples), is described via coupling of tetrapeptide -prolyl--tyrosyl--leucyl--proline methyl ester with tripeptide Boc-glycyl--valyl--proline followed by cyclization of the linear fragment having seven amino acid units. Structure of the synthesized cyclooligopeptide was confirmed by the means of chemical and spectroscopic methods including FTIR, 1H NMR, 13C NMR, FABMS and further, subjected to the anthelmintic, antibacterial and the antifungal activity studies. Bioactivity results indicated that the newly synthesized cyclic peptide displayed potent anthelmintic activity against the three earthworm species Megascoplex konkanensis, Pontoscotex corethruses and Eudrilus eugeniae at 2 mg/mL and remarkable anti-dermatophytic activities against Trichophyton mentagrophytes and Microsporum audouinii at concentration of 6 µg/mL.