The researchers believe their idea for redesigning pharmaceutical compounds so they are more biodegradable might help protect water resources in a sustainable manner.
Worldwide, water systems are gradually showing increasing contamination by micro-pollutants - including pharmaceuticals - that have the potential to harm fish and other aquatic creatures.
While the concentrations of such pollutants are fairly low, they are high enough to cause concern, and recent research shows advanced treatment of effluent may not go far enough to solve the problem in a sustainable way.
For these reasons, a team led by Klaus Kümmerer of Leuphana University of Lüneburg in Germany decided to tackle the problem from the other end - redesign commonly used drugs so they biodegrade once they reach the environment.
In a paper published in the journal Environmental Science & Technology, the researchers describe a method based on ultraviolet light that they tested on propranolol - a beta-blocker used to treat high blood pressure.
Method based on ultraviolet light
The researchers got the idea from a method that is used to remove pollutants from wastewater. Ultraviolet light can break down some compounds into more biodegradable products. Perhaps the same approach could be used to make compounds biodegradable in the first place.
The team chose to test the method on propranolol because it is a commonly used drug that does not biodegrade when it reaches wastewater, and in the concentrations found there, it is toxic to some aquatic species when they are continually exposed to it.
In their paper, the researchers describe how they dissolved the drug in pure water and exposed it to ultraviolet light for around 4 hours. This produced 16 breakdown products that they then incubated with effluent from a sewage treatment plant to test their biodegradability, which they did by measuring how much oxygen and organic carbon the microbes consumed over time.
They found that the most biodegradable derivatives were the ones that underwent changes that opened up their ring-like structure, allowing the microbes greater access to digest them.
At least one of the derivatives - a compound called 4-hydroxypropranolol - was 23% biodegraded into inorganic molecules such as carbon dioxide and water within a month.
And nearly half of the derivatives were at least partially biodegraded into other inorganic compounds predicted to be low in toxicity, the researchers note.
Using a range of techniques, the researchers found that 4-hydroxypropranolol may have drug properties similar to propranolol - something that had already been suggested in an animal study that compared the two drugs.
A 'truly sustainable' way to protect water resources
While the work is still at the proof-of-principle stage, the team believes the method could be extended to look for biodegradable alternatives for a range of pharmaceutical products, including those used in cosmetics and personal care. They conclude:
"Application of such approaches in turn might contribute to the protection of water resources in a truly sustainable manner."
Susan D. Richardson, an environmental chemistry researcher at the University of South Carolina who was not involved in the work, says the team now faces a number of hurdles. These include testing whether the derivatives are toxic to living organisms, and whether water treatment such as chlorination changes the compounds.
But, if the researchers clear these hurdles, she says their technique "could be a revolutionary way to lower our load of drugs to the environment."
Meanwhile, Medical News Today recently learned that scientists have developed a more practical and efficient way of extracting venom from deadly box jellyfish as a source of ingredients for new drugs. The method is an example of how the study of venom, which has traditionally been confined to understanding its effect as a toxin and developing antidotes, is moving into drug development.