Polar biophenolics in sweet potato greens extract synergize to inhibit prostate cancer cell proliferation and in vivo tumor growth

Carcinogenesis. 2013 Sep;34(9):2039-49. doi: 10.1093/carcin/bgt141. Epub 2013 Apr 29.


Polyphenolic phytochemicals present in fruits and vegetables indisputably confer anticancer benefits upon regular consumption. Recently, we demonstrated the growth-inhibitory and apoptosis-inducing properties of polyphenol-rich sweet potato greens extract (SPGE) in cell culture and in vivo prostate cancer xenograft models. However, the bioactive constituents remain elusive. Here, we report a bioactivity-guided fractionation of SPGE based upon differential solvent polarity using chromatographic techniques that led to the identification of a remarkably active polyphenol-enriched fraction, F5, which was ~100-fold more potent than the parent extract as shown by IC50 measurements in human prostate cancer cells. High-performance liquid chromatography-ultraviolet and mass spectrometric analyses of the seven SPGE fractions suggested varying abundance of the major phenols, quinic acid (QA), caffeic acid, its ester chlorogenic acid, and isochlorogenic acids, 4,5-di-CQA, 3,5-di-CQA and 3,4-di-CQA, with a distinct composition of the most active fraction, F5. Subfractionation of F5 resulted in loss of bioactivity, suggesting synergistic interactions among the constituent phytochemicals. Quantitative analyses revealed a ~2.6- and ~3.6-fold enrichment of QA and chlorogenic acid, respectively, in F5 and a definitive ratiometric relationship between the isochlorogenic acids. Daily oral administration of 400mg/kg body wt of F5 inhibited growth and progression of prostate tumor xenografts by ~75% in nude mice, as evidenced by tumor volume measurements and non-invasive real-time bioluminescence imaging. These data generate compelling grounds to further examine the chemopreventive efficacy of the most active fraction of SPGE and suggest its potential usefulness as a dietary supplement for prostate cancer management.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Cell Line, Tumor
  • Cell Proliferation / drug effects*
  • Chromatography, High Pressure Liquid
  • Dietary Supplements
  • Drug Synergism
  • Humans
  • Ipomoea batatas / chemistry*
  • Male
  • Mice
  • Plant Extracts / administration & dosage*
  • Plant Extracts / chemistry
  • Polyphenols / administration & dosage*
  • Polyphenols / chemistry
  • Prostatic Neoplasms / diet therapy*
  • Prostatic Neoplasms / pathology
  • Xenograft Model Antitumor Assays


  • Plant Extracts
  • Polyphenols