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Licorice Root Extract

Novel Polyphenol Molecule Isolated from Licorice Root (Glycrrhiza glabra) Induces Apoptosis, G2/M Cell Cycle Arrest, and Bcl-2 Phosphorylation in Tumor Cell Lines

Mohamed M. Rafi,† Bret C. Vastano,† Nanquan Zhu,† Chi-Tang Ho,†‡ Geetha Ghai,† Robert T. Rosen,†‡ Michael A. Gallo,‡ and Robert S. DiPaola*§

Department of Food Science and Center for Advanced Food Technology, Rutgers University, 65 Dudley Road, New Brunswick, New Jersey 08901-8520, Environmental Occupational Health Science Institute, University of Medicine and Dentistry of New Jersey, 170 Frelinghuysen Road, Piscataway, New Jersey 08854-8020, and The Cancer Institute of New Jersey, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, 195 Little Albany Street, New Brunswick, New Jersey, 08901-1914
J. Agric. Food Chem., 2002, 50 (4), pp 677–684
DOI: 10.1021/jf010774e
Publication Date (Web): December 21, 2001

Herbal therapies are commonly used by patients with cancer, despite little understanding about biologically active chemical derivatives. We recently demonstrated that the herbal combination PC-SPES, which contains licorice root, had anti-prostate cancer activity attributable to estrogen(s) that produced a chemical castration. A recent study also demonstrated that licorice root alone decreased circulating testosterone in men. Other studies demonstrated antitumor activity of PC-SPES in vitro associated with decreased expression of the anti-apoptotic protein Bcl-2 and in patients independent of chemical castration, suggesting that other mechanisms of antitumor activity exist separate from chemical castration. In the present study, we assessed licorice root extract for effects on Bcl-2 to identify novel cytotoxic derivatives. Licorice root extract induced Bcl-2 phosphorylation as demonstrated by immunoblot and G2/M cell cycle arrest, similarly to clinically used antimicrotubule agents such as paclitaxel. Bioassay-directed fractionations resulted in a biologically active fraction for Bcl-2 phosphorylation. HPLC separation followed by mass spectrometry and NMR identified 6 compounds. Only one molecule was responsible for Bcl-2 phosphorylation; it was identified as 1-(2,4-dihydroxyphenyl)-3-hydroxy-3-(4‘-hydroxyphenyl) 1-propanone (β-hydroxy-DHP). The effect on Bcl-2 was structure specific, because α-hydroxy-DHP, 1-(2,4-dihydroxyphenyl)-2-hydroxy-3-(4‘-hydroxyphenyl) 1-propanone, in contrast to β-hydroxy-DHP, was not capable of Bcl-2 phosphorylation. Pure β-hydroxy-DHP induced Bcl-2 phosphorylation in breast and prostate tumor cells, G2/M cell cycle arrest, apoptosis demonstrated by Annexin V and TUNEL assay, decreased cell viability demonstrated by a tetrazolium (MTT) assay, and altered microtubule structure. Therefore, these data demonstrate that licorice root contains β-hydroxy-DHP, which induced Bcl-2 phosphorylation, apoptosis, and G2/M cell cycle arrest, in breast and prostate tumor cells, similarly to the action of more complex (MW >800) antimicrotubule agents used clinically.


Journal of Agricultural and Food Chemistry