Isolation, identification, and biological evaluation of HIF-1-modulating compounds from Brazilian green propolis.

The tumor microenvironment is characterized by hypoxia, low-nutrient levels, and acidosis. A natural product chemistry-based approach was used to discover small molecules that modulate adaptive responses to a hypoxic microenvironment through the hypoxia-inducible factor (HIF)-1 signaling pathways. Five compounds, such as baccharin (3), beturetol (4), kaempferide (5), isosakuranetin (6), and drupanin (9), that modulate HIF-1-dependent luciferase activity were identified from Brazilian green propolis using reporter assay. Compounds 3, 9 and 5 reduced HIF-1-dependent luciferase activity. The cinnamic acid derivatives 3 and 9 significantly inhibited expression of the HIF-1α protein and HIF-1 downstream target genes such as glucose transporter 1, hexokinase 2, and vascular endothelial growth factor A. They also exhibited significant anti-angiogenic effects in the chick chorioallantoic membrane (CAM) assay at doses of 300 ng/CAM. On the other hand, flavonoids 4 and 6 induced HIF-1-dependent luciferase activity and expression of HIF-1 target genes under hypoxia. The contents (g/100g extract) of the HIF-1-modulating compounds in whole propolis ethanol extracts were also determined based on liquid chromatography-electrospray ionization mass spectrometry as 1.6 (3), 14.2 (4), 4.0 (5), 0.7 (6), and 0.7 (9), respectively. These small molecules screened from Brazilian green propolis may be useful as lead compounds for the development of novel therapies against ischemic cardiovascular disease and cancer based on their ability to induce or inhibit HIF-1 activity, respectively.

Anti-inflammatory effects of a bioavailable compound, Artepillin C, in Brazilian propolis.

Artepillin C is the major compound in the Brazilian green propolis from Baccharis dracunculifolia. Our aim in this study was to investigate the anti-inflammatory effects, absorption, and bioavailability of Artepillin C in mice. The animals used were male Swiss mice subjected to: paw oedema by carrageenan (300 microg/paw), carrageenan-induced peritonitis, and prostaglandin E(2) determination. We also measured in vitro nitric oxide production by RAW 264.7 cells and NF-kappaB activity in HEK 293 cells. Finally, we measured the absorption and bioavailability of Artepillin C in plasma from mice by means of GC-MS after a single oral dose (10 mg/kg). In vivo, Artepillin C produced a maximal inhibition of 38% after 360 min on paw oedema. Artepillin C also decreased the number of neutrophils during peritonitis (IC(50): 0.9 (0.5-1.4) mg/kg). Treatment with Artepillin C decreased prostaglandin E(2) by 29+/-3% and 58+/-5% at 1 and 10 mg/kg, respectively, with a mean ID(50) of 8.5 (8.0-8.7) mg/kg). Similarly, in in vitro models, Artepillin C (3, 10, or 100 microM) decreased nitric oxide production by RAW 264.7 cells with a mean IC(50) of 8.5 (7.8-9.2) microM. In HEK 293 cells, Artepillin C reduced NF-kappaB activity with a mean IC(50) of 26 (22-30) mug/ml), suggesting anti-inflammatory activity, particularly during acute inflammation. Lastly, Artepillin C was absorbed after an oral dose (10 mg/kg) with maximal peaks found at 1 h (22 microg/ml). Collectively, Artepillin C showed anti-inflammatory effects mediated, at least in part, by prostaglandin E(2) and nitric oxide inhibition through NF-kappaB modulation, and exhibited bioavailability by oral administration.

Suppression of tumor-induced angiogenesis by Brazilian propolis: major component artepillin C inhibits in vitro tube formation and endothelial cell proliferation.

Propolis, a resinous substance collected by honeybees from various plant sources, possesses various physiological activities such as antitumor effects. We have previously shown that propolis of Brazilian origin was composed mainly of artepillin C and that its constituents were quite different from those of propolis of European origin. In this report, we examined an antiangiogenic effects of Brazilian propolis and investigated whether artepillin C was responsible for such effects. In an in vivo angiogenesis assay using ICR mice, we found that the ethanol extract of Brazilian propolis (EEBP) significantly reduced the number of newly formed vessels. EEBP also showed antiangiogenic effects in an in vitro tube formation assay. When compared with other constituents of EEBP, only artepillin C was found to significantly inhibit the tube formation of HUVECs in a concentration-dependent manner (3.13-50microg/ml). In addition, artepillin C significantly suppressed the proliferation of HUVECs in a concentration-dependent manner (3.13-50microg/ml). Furthermore, artepillin C significantly reduced the number of newly formed vessels in an in vivo angiogenesis assay. Judging from its antiangiogenic activity in vitro and in vivo, we concluded that artepillin C at least in part is responsible for the antiangiogenic activity of EEBP in vivo. Artepillin C may prove useful in the development of agents and foods with therapeutic or preventive activity against tumor angiogenesis.

Efficient radical scavenging ability of artepillin C, a major component of Brazilian propolis, and the mechanism.

Hydrogen transfer from artepillin C to cumylperoxyl radical proceeds via one-step hydrogen atom transfer rather than via electron transfer, the rate constant of which is comparable to that of (+)-catechin, indicating that artepillin C can act as an efficient antioxidant.

First total synthesis of artepillin C established by o,o'-diprenylation of p-halophenols in water.

We have demonstrated that prenylation of p-halophenols was dependent on the solvent effect and succeeded in o,o'-diprenylation of p-halophenols in water. Following the Mizoroki-Heck coupling of the diprenyl-p-iodophenol 3c with methyl acrylate and then hydrolysis, we first synthesized artepillin C [3-(4-hydroxy-3,5-di(3-methyl-2-butenyl)phenyl)-2(E)-propenoic acid] (1), which is a biologically active constituent of propolis. These reactions may be applicable to the synthesis of various useful natural products such as 2,4,6-trisubstituted phenol derivatives.