Flavones and fatty derivatives from Bignonia magnifica (Bignoniaceae)

Bignoniaceae has about 840 species, distributed in 82 genera, that occur in a wide range of habitats, including dry environments and rainforests. The family includes trees, shrubs, vines and rarely herbaceous species.1 Bignonia genus contains 31 species and has as one of the synapomorphies the presence of glandular trichomes. These trichomes are involved in the production and secretion of exudates rich in lipophilic and phenolic compounds, and nectar.2 Bignonia magnifica is a native South American species, distributed worldwide as an ornamental plant. In literature, two studies on chemical composition report the presence of saponins, iridoids, ellagic acids and proanthocyanidins in pollen.3 To identify the foliar surface compounds, dried leaves (1200 g) were submerged for 30 seconds in dichloromethane for three consecutive times to obtain the extract (27g, 2.2%). Wax content and the leaf area was calculated using the Image J software (241.66 µg.cm-2). A portion of the extract was submitted to recrystallization in hot methanol and then left standing for 24 hours. The material was centrifuged and the soluble and insoluble portions in MeOH were obtained. Gas chromatography-mass spectrometry (GC-MS) analyzes showed the insoluble portion constituted mainly of n-alkanes (79.5%) and saturated fatty acids (14.9%). Meanwhile, HPLC-UV-DAD analyses showed two intense peaks with characteristic absorption bands of flavonoids. In order to identify these compounds, a column chromatography was performed using Sephadex LH-20 as stationary phase and MeOH as mobile phase affording four groups. Group 2 was subjected to separation in semi-preparative HPLC. Two compounds were isolated and identified through NMR spectra as eupatilin [1], a flavone with antiproliferative effect4 and 3ʹ-O-Methyleupatorin [2], a polymethoxylated flavone. This is the first report of both compounds in Bignonia genus and in the Bignoniaceae.