Making drugs more biodegradable to protect water resources

A team of scientists is working on a way to reduce the amount

of pharmaceutical pollution in our water systems by making commonly

used drugs biodegradable without impacting their effectiveness as

medicines.

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.

Written by Catharine Paddock PhD

Copyright: Medical News Today