Tropical forest loss jeopardizes discovery of new drugs

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  1. Ethnobiologists explore the world's shrinking tropical forests
  2. Forests – not big pharma – seem to hold the key on antibiotics
  3. Putting the "ant" into antibiotics

‘There are lots of plants in tropical forests that have not yet been investigated, and we’re facing an alarming grade of deforestation in tropical forests’

It has been known that deforestation is contributing to global warming for decades, but the effect it’s having on discovering new drugs has been less explored.

A recent World Health Organization report shows there is a serious lack of new antibiotics in the pipeline to combat the threat of antibiotic resistance. Globally, 700,000 people die every year because of antibiotic resistance, and by 2050 this is expected to rise to 10 million, according to a report by The Review on Antimicrobial Resistance.

But scientists believe tropical forest plants and animals could be a source of new antibiotics to replace the current failing stock.

After the so called ‘golden age’ of antibiotic discovery in the 1940s and 50s, scientists appeared to have exhausted the possibilities of the actinomycetes — a bacteria from which antibiotics can be formulated. They then moved on to new methods by creating chemical compounds in a lab.

However, billions of dollars later, that didn’t breed the results pharmaceutical companies had hoped for. Many of them abandoned work on new drugs in favor of the guaranteed profitability of improving existing ones.

But a combination of over-prescription, people not finishing their course of antibiotics, which leads to antibiotic resistant bacteria, and lack of new drug discoveries has caused a rise in antibiotic resistance. This has prompted a renewed interest in deriving new drugs from natural products, often from largely untapped environments.

One such environment is tropical forests. They cover less than 7 percent of the Earth’s surface yet are home to about 50 percent of all land animal and plant species.

Drugs used to treat malaria, cancer and glaucoma all originally came from tropical forests and around 120 prescription drugs sold globally originate from rainforest plants. Forty percent of anticancer drugs available between 1940 and 2002 were made from natural or naturally-derived products.

Quinine, which is on the World Health Organisation’s (WHO) essential medicine list, and used for treating malaria, comes from the bark of a Cinchona tree,which is found in the tropical forests of the Andes, South America. And from the Calabar bean, originating in the tropical forests of Africa, comes the drug Physostigmine, which is used to treat glaucoma – a condition where the nerve that connects your eye and brain becomes damaged and can lead to vision loss. It is the second biggest cause of blindness across the globe.

However, with more than 80,000 acres of tropical rainforest and 135 species of plants and animals being lost daily, extracting drugs from this environment in might no longer be possible in the near future.

Cassandra Quave is an “ethnobotanist” — a scientist who works on drugs derived from plant. She says: “You have mega-corporations just destroying these forests, [while] scientists like myself have great difficulty in even accessing these biological resources to study them before they’re gone.”

Tropical forests world map (CC BY SA 4.0)
Tropical forests world map (CC BY SA 4.0)


Partly because of deforestation, current extinction rates are 100-1,000 times higher than natural background rates and as many as 15,000 medicinal plants are under threat. Of known plant species, 70,000 are recogised as medicinal, let alone other potential uses such as a material or food. Predictions vary, but less than 15 percent of plant species have been screened for their medicinal potential.

amazon rainforest chopped down (CC BY 2.0)
Amazon rainforest chopped down (CC BY 2.0)

The difficult part is finding the drugs from so many plants. For every 10,000 compounds screened for medicinal properties, about 250 make it to clinical trials, according to Milken Institute Review. Of those only one will eventually become an approved drug.

Ethnobotanists fight back

Ethobotanist Quave, who studies plants and their practical applications using indigenous knowledge, describes her endeavors as a “lost art.”

She leads an antibiotic drug discovery research team at Emory University, Atlanta, Georgia. The Quave Research Group is looking for what are called ‘antibiotic potentiators.’ They can be used to restore effectiveness to antibiotics that have been rendered impotent by bacterial resistance. Her team is looking for treatments for super fungus Candida Auris, which is resistant to many drugs.

Quave also wants to draw attention to curing fungal infections, as she says there are few chemical classes that currently treat them.

Cassandra Quave in lab (CC BY SA 3.0)
Cassandra Quave in lab (CC BY SA 3.0)

The team she leads extracts chemical compounds from plants, traditionally used as medicines, to produce drugs. Most pharmaceutical labs now synthetically make the chemical compounds drugs derive from. But the Quave Group takes the natural approach: her team now has around 1,200 extracts from more than 400 different species it has collected.

The plants shipped in to the university come from the south-east U.S. – states like Georgia and Florida – and countries in the Mediterranean basin and Balkans, including Italy, Albania and Lebanon. However, Quave still gets out in the field. This summer she was out with students working on the Aeolian islands, off the coast of Sicily, because of the islands’ remoteness and endemic species.

Quave says she would like to be able to study plants from tropical forests too, but that it’s very difficult to get permits to take plant samples from countries in this environment.

“I think that there are lots of plants in tropical forests that have not yet been investigated, and we’re facing an alarming grade of deforestation in tropical forests, due to mining, logging and gold and natural resource extraction that’s just destroying large tracks of land … tropical forests are definitely one of those high risk areas where we are rapidly losing those resources for drug discovery.”

Cassandra Quave in Sicily with plant samples (CC BY-SA 3.0)
Cassandra Quave in Sicily with plant samples (CC BY-SA 3.0). Instagram quaveethnobot

She is also concerned by the loss of collective memory from tribes who have used medicinal plants for thousands of years.

“We use that lens of culture also in our drug discovery efforts … knowledge of how those [plants] have been used over centuries for food and medicine, and survival,” she says. “It is important to highlight the need to record these things [plants], and help preserve these areas, and create safe havens for these people before it’s all gone.”

Ants were using antibiotics before humans

A microbiologist at the University of East Anglia, Matt Hutchings, is leading a team looking for sources of antibiotics in the nests of leafcutter ants which live in central and South America. Leafcutter ants could provide major breakthroughs for new antibiotics. The last natural product antibiotic to be introduced was daptomycin, discovered in 1987, so new drugs are desperately needed.

Microbiologist Matt Hutchings UEA with leafcutter ants
Microbiologist Matt Hutchings UEA with Acromyrmex echinatior leafcutter ants (Credit: CC BY SA 3.0 Matt Hutchings University of East Anglia)

He works with Acromyrmex echinatior leafcutter ants collected in Gamboa, Panama. They gather leaves in the rainforest and feed them to a fungus known as Leucoagaricus gongylophorus, which in return supplies them with food. Antibiotic-producing bacteria which live on the ants, known as actinomyces, are the raw material for 60 percent of known antibiotics. The ants feed the bacteria living on them through specialized glands in their exoskeletons and use the antibiotics produced by these bacteria to kill off other microbes that would otherwise infect their fungus garden. If the ants smell infected parts of the fungus they remove it, dump it away from the nest and use anti fungal antibiotics on it to sterilize it. Ant species that farm fungi (Attini antshave most likely been using antibiotics for more than 50 million years to protect these fungus gardens from pests.

The team Hutchings leads is isolating bacteria from the ants, and seeing if the antibiotics they produce prevent other harmful bacteria from growing. He says the team have identified antibiotics which could be very powerful against ‘superbugs’ like MRSA.

And while Hutchings believes only 10 percent of the antibiotics that are made by actinomyces have been discovered, leaving huge room for potential, he says the problem boils down to finances.

“Who wants to invest billions of dollars to find new antibiotics? Drug companies don’t want to pay for it. Governments can’t afford to pay for it. Antibiotics don’t make any money, basically.”

Hutchings says while the antibiotics we have are fantastic but we have used them badly.

“They’ve just been giving them out like Smarties, which is the worst thing you can do.”

He hopes now we’ve learned our lesson.

“So when we develop a new generation of antibiotics, they’ll be used very carefully.”



Leafcutter ants fungus garden chamber
Leafcutter ants fungus garden chamber (Credit: CC BY SA 3.0 Matt Hutchings University of East Anglia)


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