White poplar: Targeted isolation of pancreatic lipase inhibitors

In order to discover new anti-obesity agents, twenty two natural extracts from medicinal plants and agricultural wastes were screened by pancreatic lipase inhibition assay. The methanolic extract of poplar wood (Populus alba L.), an important raw material for paper industry, showed promising inhibitory activity, its IC₅₀ value was 7.15 μg/mL. Through bio-guided fractionation, the ethyl acetate fraction (E) was found to be the major contributor to the activity, IC₅₀ = 4.7 μg/mL. Hence, it was subjected to bio-guided isolation and nine compounds (1–9) were identified from the active sub-fractions. The isolates were identified by means of one- and two-dimensional nuclear magnetic spectroscopy (1D, 2D-NMR), as well as high-performance liquid chromatography quadrupole time-of flight mass spectrometry (HPLC-QTOF-MS). (+)-Taxifolin (5) and (+)-ampelopsin (4) showed the highest activity, their IC₅₀ values were 23.2 and 46.2 μM, respectively. The results indicated that flavonoids and phenolic acids in poplar wood could serve as potential candidates for development of new anti-obesity agents.