Martefragin A, a Novel Indole alkaloid Isolated from Red Alga, Inhibits Lipid Peroxidation

Abstract

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