A new stereoisomer Meso-araguspongine C together with nine reported macrocyclic bis-quinolizidine alkaloids araguspongines A, C, E, L, N-P, petrosin, and petrosin A were isolated from marine sponge Xestospongia muta. Stereochemistry of meso-araguspongine C (2) and araguspongines N-P (3-5) were established by their NMR data and conformational analyses. Both araguspongine C (1) and meso-araguspongine C (2) exhibited great cytotoxic activity towards HepG-2, HL-60, LU-1, MCF-7, and SK-Mel-2 human cancer cells (IC50 in the range of 0.43-1.02 μM). At a concentration of 20 μM, isolated compounds (1-10) also showed modest inhibitory effects (from 7.6 to 40.8%) on the NO production in LPS activated RAW264.7 macrophages.
Keywords: araguspongine C; quinolizidine alkaloid; cytotoxicity.