Composition of Algerian Propolis, Plant Origin, and Its Antiangiogenic Activity In Vitro.

The antiangiogenic activity of the ethanol extract of propolis collected from different regions in western Algeria was investigated using in vitro human umbilical vein endothelial cells (HUVECs). The ethanol extract with the strongest activity, i.e., Algerian propolis 1 (EEPA1), inhibited the formation of capillary networks in a dose-dependent manner (6.25-50 µg/mL) within 12 h and induced cell fragmentation of HUVECs at 50 µg/mL after treatment for 24 h. To identify the active compounds in EEAP1, a high-performance liquid chromatography (HPLC) analysis was performed, revealing that EEAP1 contains two major compounds. Both compounds were isolated by repeated column chromatography and identified as ω-hydroxyferulenol (1) and ferulenol (2), which have a coumarin structure conjugated with a farnesyl group according to NMR, high-resolution electrospray ionization mass spectroscopy, and chemical modification. Compounds 1 and 2 inhibited the tube-forming activity of HUVECs, especially 2, which exhibited a stronger antiangiogenic effect even at a low concentration of 3.31 µg/mL. Moreover, 2 suppressed the elongation and induced cell fragmentation at the same dose. The molecular changes in tube-forming HUVECs induced by 2 were found to be related to the activation of the caspase signals. To confirm the plant origin of propolis, an HPLC comparative analysis of the ethanol extracts of some plants near beekeeping areas and that of Algerian propolis (EEAP1) was performed, and similar chromatographic patterns were observed. This result suggests that the plant origin of this Algerian propolis is the resin of Ferula communis.

Nymphaeol-A Isolated from Okinawan Propolis Suppresses Angiogenesis and Induces Caspase-Dependent Apoptosis via Inactivation of Survival Signals.

Propolis, a resinous substance that honeybees collect to protect their beehive from enemies, is reported to have various biological activities. In our screening program to search for antiangiogenic compounds from propolis, the ethanol extracts of Okinawan propolis (EEOP) showed significant antiangiogenic activities in a tube formation assay with human umbilical vein endothelial cells (HUVECs) in vitro at 3.13 µ g/mL and chorioallantoic membrane (CAM) assay in vivo at 25 µ g/egg. To elucidate the active compounds of EEOP and their mode of action, we isolated some prenylated flavonoids from EEOP and found that nymphaeol-A had the strongest antiangiogenic activity among them. Nymphaeol-A significantly reduced in vivo neovessel formation in the CAM assay at 25 µ g/egg. At the molecular level, nymphaeol-A markedly inactivated mitogen-activated protein kinase/ERK kinase 1/2 (MEK1/2) and extracellular signal-regulated kinase 1/2 (ERK1/2), whose molecular activations signal new vessel formation in HUVECs. In addition, nymphaeol-A dose- and time-dependently induced caspase-dependent apoptosis in tube-forming HUVECs. Taken together, nymphaeol-A was shown to inhibit angiogenesis at least in part via inactivation of MEK1/2-ERK1/2 signaling and induction of caspase-dependent apoptosis. Okinawan propolis and its major component, nymphaeol-A, may be useful agents for preventing tumor-induced angiogenesis.