Axinellamine E, One New Pyrrololactam Alkaloid from the South China Sea Sponge Axinella sp.

Chemical investigation of the EtOH extract of the sponge Axinella sp. collected from the South China Sea resulted in the identification of one new pyrrololactam alkaloid, axinellamine E (2), along with four known analogs (1, 3-5). Compound 1 was initially separated as enantiomers and was further separated to be optically pure compounds (1 a and 1 b) by a chiral column. The planar structure of compound 2 was determined mainly by 1D-, 2D-NMR, and HR-ESI-MS data analyses. Absolute configurations of 1 a and 1 b was defined by calculated ECD spectra method. All of the compounds were evaluated for their anti-inflammatory activities against nitric oxide production in lipopolysaccharide-induced RAW 264.7 cells among which compound 1 showed weak activity at 40 μg/mL. Plausible biosynthetic pathways corresponding to aldisine analogs of 1, 2, 4, and 5 were also discussed.