Potential anti-inflammatory activities of bractelactone and other compounds isolated from Fissistigma bracteolatum

From the stems of Fissistigma bracteolatum. a novel natural product with an unprecedented skeleton, bractelactone (1). was isolated, together with four known compounds: piperolactam A (2), aristololactam BIII (3), aristololactam BII (4). and fissilandione (5). The structure of 1 was established on the basis of spectroscopic data as (3Z)-6,7-dihydroxy-4-methoxy-3-(phenylmethylidene)-5-(3- phenylpropanoyl)-1-benzofuran-2(3H)-one. This compound may be derived from a hybrid of a chalcone and a cinnamic acid, or from a degradation product of a dichalcone. Compounds 1, 2, and 5 showed inhibitory effects on NO generation by RAW264.7 macrophages in response to lipopolysaccharide. Compounds 2 and 5 showed inhibitory effects on formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP)-induced superoxide anion (O₂^.-) generation in human neutrophils.