Isolation and structure of axinastatin 4 from the western indian ocean marine sponge Axinella cf. carteri

The Republic of The Comoros marine sponge Axinella cf. carteri has been found to contain a cell growth inhibitory (P388 lymphocytic leukemia cell line ED₅₀ 0.057 μg/ml, and comparable activity against a series of human cancer cell lines) cyclo-heptapeptide named axinastatin 4 (3). The new peptide was obtained in 1.0 × 10^-6% yield (6.1 mg) from 600 kg (wet wt) of the sponge. The structure of axinastatin 4 was deduced as cyclo-(Pro-Leu-Thr-Pro-Leu-Trp-Val) by a combination of high field (400 and 500 Mhz) 2D nmr (¹H-¹H, ¹H-¹³C, HMBC and NOE) and high resolution mass spectral (principally by ms/ms) measurements and subsequent interpretations.