Monday, November 05, 2007

Drugs That Are Easier on the Environment

Pharmaceuticals from natural sources could be easier to find and cleaner to make, thanks to a new catalyst.

By Kevin Bullis

Green chemistry: Christina White, a professor of chemistry at the University of Illinois at Urbana-Champagne, and her colleague Mark Chen, a postdoctoral researcher, have developed a new iron-based catalyst (bottom) that could reduce toxic waste and lead to new drugs. White is holding a bottle of hydrogen peroxide, an environmentally friendly oxidant used with the catalyst, and Chen holds a beaker containing the catalyst (top). Credit: Christina White

A new environmentally friendly catalyst could make it much easier to discover new drugs based on natural sources. Researchers at the University of Illinois at Urbana-Champagne have shown that an iron-based catalyst could be used to turn promising natural products into effective medications by selectively altering complex molecules to make them more bioactive.

The catalyst could also streamline the process of synthesizing other drugs, reducing toxic waste in the form of heavy metals and chlorine. Christina White, a professor of chemistry at the University of Illinois who led the research, hopes that her work will benefit human health. She says that the new catalyst, described in the current issue of Science, could help companies "make drugs better and potentially discover drugs faster."

Many of the most effective medications have been derived from natural sources, says Steve Brickner, a research fellow at Pfizer, based in New York, who is involved in drug discovery. "The bulk of antibiotics on the market come from natural products," he says. "The ability to manipulate complex molecules of natural-product origin, as [White's team has] done, is really very exciting."

Using conventional techniques to sort through promising natural products can be an arduous process. A natural product, typically in the form of a complex molecule, may be too weak to be an effective drug. But changes to the core of the molecule could make it much more potent. The problem is that because the molecules are complex, and the target bonding sites are inert and difficult to modify specifically, even such a minor change can be difficult or impossible. As a result, chemists often have to synthesize the molecules from scratch, a cumbersome and complicated process. White's catalyst lets researchers make specific changes to normally difficult-to-modify bonds in complex natural molecules, which could allow chemists to much more easily sort through possible new drugs. White demonstrated this capability by modifying artemisinin, a complex natural antimalarial compound, into a related compound that could prove more effective.

Brickner says that the catalyst may help researchers discover new drugs in another way. Chemists screen the metabolites that are produced when organisms process candidate drugs, and sometimes the metabolites could themselves be the basis for powerful drugs. With White's catalyst, it may be much easier to work with such metabolites.