New oleanane saponins from the roots of Dendrobangia boliviana identified

Abstract

Dendrobangia is a genus from the Cardiopteridaceae family, composed of 43 species grouped in 6 tropical genera. This genus is composed of three species, D. multinerva Ducke, D. tenuis Ducke, and D. boliviana Rusby, large trees growing in the tropical areas. Dendrobangia boliviana Rusby is a tree widely distributed in the Neotropical region of America from Costa Rica to Brazil and Bolivia. It can be from 5 to 30 m high and up to 50 cm in diameter. It grows mainly in mountain forests and more rarely in floodplain forests, in an altitude of 100 to 1200 m. It tolerates a wide range of soils. In Colombia, the community of the region Hibito consumes the fine fruits in their dried form. The wood of this tree is very hard and therefore used in construction, for furniture, sporting goods, tool handles and interior coverings. In order to discover new secondary metabolites of biological importance from Peru’s Amazon rainforest, we investigated in a previous phytochemical study the roots of D. boliviana and isolated fourteen oleanane saponins which are glycosides of serjanic or phytolaccinic acid. In order to push our investigation further, the saponin enriched fractions were analyzed using a hyphenated LC-SPE-NMR system in order to identify as many compounds as possible. This methodology has been widely used for the structure elucidation of natural products from complex mixtures. The joint use of LC and solid-phase extraction (SPE) results in more concentrated samples and therefore improves the signal to noise ratio of NMR spectra achievable within a given period of time. It appeared as a timesaving method with a broad application range. As a result, the LC-SPE-NMR study allowed us to identify five new saponins, together with twelve known saponins already identified in these roots and another known saponin from another plant species. Their structural characterization has been carried out through NMR spectroscopy and mass spectrometry studies.