Nortriterpenes, chromones, anthraquinones, and their chemosystematics significance in Meliaceae, Rutaceae, and Simaroubaceae (Sapindales)

In this review, our analyses of the metabolic routes of limonoids and quassinoids—with respect to their occurrence in the families Rutaceae, Meliaceae, and Simaroubaceae—suggest a disjunction between the Simaroubaceae (characterized by quassinoids) and the Rutaceae and Meliaceae (distinguished by limonoids). However, even with the latter two families, clear-cut chemical differences could be discerned. Meliaceae exploit different biogenetic pathways, which lead to more diverse limonoids than in Rutaceae. The complex limonoids and prenylated chromones isolated from Spathelia, Sohnreyia, Dictyoloma, Harrisonia, Cneorum, and Cedrelopsis provided firm support for including them into the Cneoroideae. Ptaeroxylon produces several types of chromones, justifying to include it near the allied taxa, also into Cneoroideae. However, considering the complex limonoids found in Flindersia and Hortia, their connections to the Rutoideae subfamily were thus rather difficult to envisage; they suggest a closer relationship with the Cneoroideae genera. Until recently, there was no chemical evidence to support the placement of Picramnia into Simaroubaceae or near the allied taxa Rutaceae and Meliaceae. However, our investigations revealed several nortriterpenes involving expansion of the A-ring to a 4,4-dimethyl-tetrahydro-2H-furo[1,10]pyran-3(6H)-one as in limonin-type limonoids, whose derivatives have been isolated from Rutaceae genera. In addition, liquid chromatography-tandem mass spectrometry-(MS/MS)-based molecular networking showed profiling of quassinoids from P. glazioviana. These data convincingly point to affinities between Picramnia species and Cneoroideae genera, suggesting Picramniaceae is sister to Rutaceae, Simaroubaceae, and Meliaceae.