Pheophorbide a, a major antitumor component purified from Scutellaria barbata, induces apoptosis in human hepatocellular carcinoma cells

• Published in: Planta medica Vol. 72; no. 1; pp. 28 - 33
• Main Authors: Chan, J.Y.W, Tang, P.M.K, Hon, P.M, Au, S.W.N, Tsui, S.K.W, Waye, M.M.Y, Kong, S.K, Mak, T.C.W, Fung, K.P
• Format: Journal Article
• Language: English
• Published: Germany 01.01.2006
• Subjects: anticarcinogenic activity; Antineoplastic Agents, Phytogenic - analysis; Antineoplastic Agents, Phytogenic - pharmacology; Antineoplastic Agents, Phytogenic - therapeutic use; apoptosis; Apoptosis - drug effects; Blotting, Western; Carcinoma, Hepatocellular - drug therapy; Cell Line, Tumor; Cell Proliferation - drug effects; Chemical Fractionation; chemical structure; Chlorophyll - analogs & derivatives; Chlorophyll - analysis; Chlorophyll - pharmacology; Chlorophyll - therapeutic use; cultured cells; cytotoxicity; DNA Fragmentation; Flow Cytometry; Humans; medicinal plants; Molecular Structure; pheophorbide; phytochemicals; Plant Extracts - chemistry; Plant Extracts - pharmacology; Plant Extracts - therapeutic use; Scutellaria; Scutellaria - chemistry; Scutellaria barbata; traditional medicine
• ISSN: 0032-0943; 1439-0221
• DOI: 10.1055/s-2005-873149

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.