Pheophorbide a, a major antitumor component purified from Scutellaria barbata, induces apoptosis in human hepatocellular carcinoma cells.
Scutellaria barbata has long been used as a Chinese medicine for the treatment of liver diseases such as hepatitis and hepatocellular carcinoma. In the present study, a bioassay-guided method was used to isolate the most active components from Scutellaria barbata. The anti-proliferative effects on human hepatoma HepG2 and Hep3B cells of each fraction at every stage of the purification were monitored. An active component, which is 97% pure by high performance liquid chromatographic analysis, was isolated. Based on nuclear magnetic resonance (NMR) and mass spectrophotometric (MS) analysis, this active component was identified to be pheophorbide a (C35H36N4O5). Mechanistic studies showed that pheophorbide a induced apoptosis in Hep3B cells, a viral-induced hepatoma cell line. However, it was found to be non-toxic in normal human liver cells WRL-68. DNA fragmentation, sub-G1 cell cycle arrest, as well as suppression of the anti-apoptotic protein Bcl-2, release of cytochrome c to the cytosol, and activation of pro-caspase 3 and pro-caspase 9 were observed when Hep3B cells were treated with 40 microg/mL (i. e., 67.5 microM) pheophorbide a for 48 hours. In conclusion, this is the first report describing the isolation of pheophorbide a from Scutellaria barbata using a bioassay-guided isolation method. The anti-proliferative activity and possible mechanisms of action of pheophorbide a on hepatoma Hep3B cells are also discussed.
Chan
Judy Yuet-Wa
JY
Department of Biochemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
Tang
Patrick Ming-Kuen
PM
Hon
Po-Ming
PM
Au
Shannon Wing-Ngor
SW
Tsui
Stephen Kwok-Wing
SK
Waye
Mary Mui-Yee
MM
Kong
Siu-Kai
SK
Mak
Thomas Chung-Wai
TC
Fung
Kwok-Pui
KP
D000972:Antineoplastic Agents, Phytogenic / Q000032:analysis / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D005591:Chemical Fractionation; D002734:Chlorophyll / Q000031:analogs & derivatives* / Q000032:analysis / Q000494:pharmacology / Q000627:therapeutic use; D053938:DNA Fragmentation; D005434:Flow Cytometry; D006801:Humans; D015394:Molecular Structure; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use; D031363:Scutellaria / Q000737:chemistry*
D000972:Antineoplastic Agents, Phytogenic; D010936:Plant Extracts; D002734:Chlorophyll; C032623:pheophorbide a