Sclerin, a New Cytotoxic Cyclononapeptide from <i>Annona scleroderma</i>

Abstract

A new cytotoxic cyclononapeptide, sclerin, cyclo(⁻Dab1⁻Ser2⁻Tyr3⁻Gly4⁻Thr5⁻Val6⁻Ala7⁻ Ile8⁻Pro9⁻) (1), was isolated from the methanol extract of the seeds of Annona scleroderma, together with the known metabolite, cyclosenegalin A, cyclo(⁻Pro1⁻Gly2⁻Leu3⁻Ser4⁻Ala5⁻Val6⁻Thr7⁻) (2). The planar structures for the two compounds were established by comprehensive analysis of NMR and ESI-HRMS data, and the absolute stereochemistry was stablished by Marfey’s method. Compound 1 showed moderate cytotoxic activity against the human prostate carcinoma cell line DU-145 at µM concentration.

Keywords

• cyclopeptide
• cyclononapeptide
• cytotoxic compound
• <i>Annona</i>