For more than 15 years, Zhijun Liu with the School of Renewable Natural Resources has been investigating plants for medicinal properties. He started by looking at plants that traditionally have been used as folk remedies to treat diseases such as hypertension, diabetes and cancer.
For the past 10 years, his focus has been on angiogenesis inhibitors, hoping to find compounds that will prevent the growth of blood vessels and can be used to treat diseases such as cancer, obesity and psoriasis.
“Inhibiting angiogenesis can prevent cancer – and perhaps even fat tissue – from developing beyond the simple limits of existing blood vessels,” he said.
Turning these discoveries into practical therapies presents major obstacles, which are typical in the use of botanical extracts for health care and therapeutics, Liu said.
“To be effective, the active ingredients must be concentrated enough to achieve a therapeutic effect,” he said.
Liu first screens extracts by fractionating – dividing the material into smaller segments – and then further subdivides the fraction that holds the most promise for delivering an effective compound. Finally, he purifies the extract fraction to produce an effective concentration of the compound.
“We use bioassay-directed isolation to trace down the molecules responsible, then expand to similar chemical structures,” Liu said.
Through laborious isolation he has identified gallic acid as a contributor to angiogenesis inhibition. Then he began looking for derivatives – analogs of gallic acid from other sources.
In Chinese sweet tea, for example, the extract did a better job of inhibiting angiogenesis than gallic acid alone.
“Based on bioactivity, we determined that the effect was not because of a single molecule,” Liu says. “Three different chemicals in an appropriate proportion behave synergistically.”
Liu believes he and his colleagues are on the threshold of a breakthrough.
“I used to start with the plant and not stop until I found the molecule,” Liu said. “Now, I realize it may not be one compound but several compounds. My interest now is to see if they’re synergistic. That’s the beauty of natural plants – they produce synergistic compounds.”
(This article was published in the summer 2009 issue of Louisiana Agriculture.)