MARTEFRAGIN-A, A NOVEL INDOLE ALKALOID ISOLATED FROM RED ALGA, INHIBITS LIPID-PEROXIDATION

Martefragin A (1), a novel indole alkaloid, was isolated from a red al ga, Martensia fragilis, by repeated column chromatography, The structu re of 1 was elucidated on the basis of spectral analysis of its methyl ester (2), including H-1- and C-13-NMR, H-1-H-1 correlation spectrosc opy (COSY), and C-13-H-1 COSY, A single crystal X-ray analysis of the hydrochloride of 1 confirmed the assignment. Martefragin A (I) showed inhibitory activity on NADPH-dependent lipid peroxidation in rat liver microsomes. The IC50 values of 1, alpha-tocopherol and ascorbic acid were 2.8, 87 and 200 mu M, respectively.