A bioassay-guided phytochemical investigation on the methanol extract of
Boehmeria pannosa, using a HIF-1-mediatedreporter gene assay, led to the isolation of two phenanthroquinolizidine alkaloids, (-)-cryptopleurine (
1) and (-)-(15
R)-hydroxycryptopleurine (
2). The structure of the new compound
2 was determined by spectroscopic methods.Compounds
1 and
2 potently inhibited the hypoxia-induced expression of a reporter gene under the control of a hypoxiaresponse element (HRE) with IC
50 values of 8.7 and 48.1 nM, respectively. Furthermore,
1 and
2 suppressed theaccumulation of HIF-1
![](/images/gifchars/alpha.gif)
protein in a dose-dependent manner, but not the HIF-1
![](/images/gifchars/beta2.gif)
protein and inhibited expression ofvascular endothelial growth factor (VEGF) by hypoxia.