Limonoids of the phragmalin type from Swietenia macrophylla and their chemotaxonomic significance.

Species of Swietenia elaborate limonoid chemistry along only one route, which leads to the mexicanolide type in most species and the phragmalin type in S. mahogani. A hexane extract from leaves of S. macrophylla afforded six new phragmalins with a 8,9,30-ortho-ester unit, namely, 6-O-acetylswietephragmin E (1), 3β-O-destigloyl-3β-O-benzoyl-6-O-acetylswietephragmin E (2), 12α-acetoxyswietephragmin C (3), 3β-O-destigloyl-3β-O-benzoyl-12α-acetoxyswietephragmin C (4), 12α-acetoxyswietephragmin D (5), and 3β-O-destigloyl-3β-O-benzoyl-12α-acetoxyswietephragmin D (6). This appears to be the first record of phragamalins from S. macrophylla, and this study shows the potential of tricyclic [3.3.12,10.11,4]-decane limonoids as taxonomically useful chemical markers in the Meliaceae.