From the EtOAc extract of the latex of Jatropha gossypifolia (Euphorbiaceae) collected in Senegal, a new cyclic octapeptide, cyclogossine B (1), was isolated together with the known cyclic heptapeptide cyclogossine A. The structure of 1 was elucidated by chemical degradation, mass spectrometry, and homonuclear and heteronuclear NMR experiments. Acid hydrolysis and HPLC analysis revealed the amino acid composition of 1 as Ala (2), Gly (2), Ile (1), Leu (2), and Trp (1). The absolute stereochemistry of all residues was shown to be the L-configuration. The molecular formula C39H59N9O8 (molecular weight 781) was deduced from HRLSIMS. The amino acid sequence was determined via 1H-1H COSY, HOHAHA, ROESY, and HMBC experiments, and supported by LSIMS spectra.