Digestive glands extraction and precise pigment analysis support the exclusion of the carnivorous plant Dionaea muscipula Ellis from the Caryophyllales order

Abstract

In the order Caryophyllales, plants synthesize betalains instead of anthocyanins, with only two exceptions, the Caryophyllaceae and Molluginaceae. Dionaea muscipula Ellis was included in the Caryophyllales order but recent research based on genetic studies proposed the consideration of the Droseraceae family into the Nepenthales order. In this work we face the dilemma of the phylogenetic classification of Dionaea from a phytochemical point of view. Dionaea’s pigments were analyzed by using techniques of structural analysis. Extracts from the leaves, mature stem and flowers of different specimens of Dionaea were analyzed, to find possible differences in the types of pigments or in their proportion in different parts of the plant. These extracts were analyzed by spectrophotometry, HPLC co-elution and ESI-MS/MS. In addition, digestive glands were extracted from the snap trap with minor sample manipulation and by reducing the non-pigmented plant tissue. Considering only the digestive glands instead of whole snap traps, the analyses allowed to quantitate and elucidate the structure of the compounds responsible for the red coloration: delphinidin-3-O-glucoside (myrtillin), cyanidin-3-O-glucoside (kuromanin) and a third compound, the aglycone cyanidin, detected in the species for the first time. The unambiguous results of the present work support the exclusion of Dionaea from the Caryophyllales.