What does biodiversity loss mean to drug discovery?
Snowdrops were traditionally used to relieve headaches. However, they are now believed to slow down the progression of dementia. Galantamine, a natural alkaloid extracted from bulbs in the 1950s was discovered. A synthetic version of this drug is used today to treat Alzheimer's disease. Scientists are also investigating whether snowdrops could be effective in HIV treatment.
Over-harvesting has led to many endangered snowdrop species. The snowdrop is not the only plant that could provide new medicines. They also offer chemical templates that can be used to create novel drugs. Scientists around the world believe that unsustainable wild medicinal plant use is a contributing factor to biodiversity loss, which could impact the ability to obtain medicines from nature in future.
Dr Cassandra Quave is a medical ethnobotanist, and an associate professor at Emory University in Atlanta, Georgia. She says that just when we most need them, we run the risk of losing important species.
Long history of good health
In Youyang (China), a farmer harvests sweetwormwood trees. Tu Youyou, a Chinese pharmacist, discovered artemisinin in 1972, a treatment for malaria. Photograph: Michael Reynolds/EPA
Since before the invention of written language, humans have used nature to heal. A Nagpur slab of clay dating back to 5,000 years was the first evidence. It contains information about more than 250 plants. The history of traditional Chinese medicine goes back thousands of years. The earliest written evidence was found on pieces of tortoiseshell or bone in the 15th century BC. The 3,500-year-old Egyptian scroll called the Ebers papyrus mentions that willow bark was used to make aspirin.
Dr Melanie-Jayne Howes is the Kew Gardens' lead researcher in biological Chemistry. She explains how they use traditional remedies and then investigates to determine if there is any scientific basis.
This is how the antimalarial drug artemisinin was created. It can be found in sweetwormwood. Sweet wormwood has been used for thousands of years in traditional Chinese medicine to treat fevers. This can be a sign of malaria. Artemisinin, and its derivatives, play an important role in the fight against malaria.
The greatest killers in human history
Scientists have discovered a compound in European chesnut trees that can neutralise drug resistant staph bacteria, inspired by an old Italian remedy. Photograph by Steidi/Alamy
Penicillin, Morphine, and some of our most powerful cancer chemotherapeutics are all derived from natural sources. Many of humanity's greatest killers, such as heart disease and cancer, can be treated with medicines that come from plants and fungi. The World Health Organization estimates that 11% of all the essential medicines in the world are derived from flowers.
Farnesol, which is found in herbs and fruits, has been discovered to be effective in treating Parkinson's disease. Recent research has shown that water hyssop can reduce inflammation in the brain. This herb, which has been used for centuries in Asia to improve brain function and health, was recently discovered to be less effective. A protein from beetroot has been identified as a potential target for neurodegenerative or inflammatory diseases such as Alzheimer's and multiple sclerosis.
Scientists discovered a molecule from the European chestnut tree's leaves that could neutralize dangerous and drug-resistant staph bacteria in June. They hope to synthesise a drug that will treat methicillin-resistant Staphylococcus aureus (MRSA) despite its resistance to antibiotics.
Quave states: It was not uncommon to die of infection in the pre-antibiotic era. A simple cut in the garden can lead to a fatal disease. Antimicrobial resistance could be a return to the same conditions as before: the post-antibiotic era. Today, we lose an estimated 700,000 people across the globe each year due to antimicrobial-resistant (AMR) infections. AMR infections will cause 10 million deaths per year by 2050, according to estimates. These and other emerging health threats can be defeated only if nature is in control, according to me.
A deep-sea cure for cancer
Horseshoe crabs' blue blood is sensitive to toxic bacteria. It is widely used for detecting impurities in vaccines such as Covid-19. Photograph: Mike Segar/Reuters
There are medicines in every corner of the Earth. The hairs of sloths may contain fungi that could be used to combat parasites, bacteria, and cancer. Heart conditions can be treated with snake venom-derived medicines. Scientists even found a marine bacterium that lives at depths up to 6500ft. They hope it could be used as a treatment for aggressive brain cancer.
Covid vaccines were developed using the bright-blue blood from the horseshoe crab
The resources of nature can also be used for research and medical purposes. The bright-blue blood of the horseshoe crab has long been used to detect impurities in medicines and vaccines and was used in the development of Covid vaccines.Micro-algae, known as diatoms, have porous cell-wall structures so can be used as vehicles for drug delivery into the body. They are being studied for their potential use in immunotherapy or combination therapy to treat the disease.
Others take their inspiration from nature. The ability to mimic the barnacle-like adhesive helps wounds heal faster. In urinary catheters, and deep-wound dressings, a sharkskin-inspired, bacteria resistant material is used. The hypodermic needle mimics the mosquitos proboscis and promises painless injections.
We know so little!
Catharanthus roseus, the Madagascar periwinkle, is a natural source for vincristine that can be used to treat childhood leukemia. Photograph: Narayan Maharjan/NurPhoto/Rex/Shutterstock
We are actually losing species even before we realize it. The main causes of biodiversity loss are pollution, over-exploitation, introduction of invasive species and change in land use and degradation due to human activity. Experts are now asking if biodiversity loss could pose as much a threat as climate change to human health.
In less than 50 years, the wildlife populations have declined by more than two-thirds World Wildlife Fund
Howes states that humans have only managed to harness the unique properties of a small number species. Vincristine is used in the treatment for children's leukemia and vinblastine is used to treat Hodgkins Disease.
It is believed that the rate of species loss is between 1,000 and 10,000 times greater than the natural rate of extinction. However, it is impossible to know how many species exist on Earth. Estimates range from 5.3m to 1tn. We do know, however, that the rate at which species disappear is increasing. According to the WWF, wildlife populations have declined by more than two-thirds within 50 years. The International Union for Conservation of Nature's (IUCN), however, estimates that nearly a third of all species are at risk of extinction.
This is the most diverse group of all
The Polybia paulista wasp is believed to be capable of killing cancer cells with its venom. Photograph by JudsonCastro/Getty Images/iStockphoto
Ross Piper is an entomologist as well as a zoologist at the University of Leeds. He says that we have barely scratched the surface of potential pharmaceutical uses for this most diverse group of living creatures.
Piper states: Although we have described over a million insects, there are many more. Even those that do have names, that's about all we know. We don't know much about ecology. We are certain to lose unique species in the universe with every bit of habitat lost.
There are insects in almost every habitat, both terrestrial and freshwater. Insects have developed a wide range of chemical cocktail to protect themselves and prey on the many organisms they encounter. These include antimicrobial compounds made by larvae that can be used to fight viruses and tumors, as well as venoms such as the Polybia paulista wasp which is believed to kill cancer cells.
Because of the large number of insects that are available, it is often difficult to find specimens with medical value. It is difficult to keep insects in captivity. Also, because they are so small it is difficult to extract enough of the useful material. Scientists can now extract the entire genome of an organism.
Piper says it has been neglected in the past. Piper says that in the past research was restricted to species that could easily be raised in captivity in large numbers. This included soldier flies and crickets. We can now get enough from a few individuals rather than thousands of people.
Future generations will need medicines
The endangered pacific yew is being used to make the chemotherapy drug Paclitaxel. Photograph by George Ostertag/Alamy
According to Kew Gardens' 2020 report, the driving factor for biodiversity loss is the rise in demand of naturally derived medicines. The horseshoe crab, which is one of the most endangered species, is now considered vulnerable. In Taiwan, the tri-spine horseshoe cat is extinct. IUCN has classified the Pacific yew as a near-threatened species. Its population is in a downward spiral towards extinction.
Howes says that it took thousands of Pacific yews to produce enough paclitaxel to be clinically effective. She explained how scientists can gain a better understanding of plant chemistry to find sustainable ways to extract medicines from nature in order to preserve essential medicines for future generations.
Now we have a better understanding of biosynthetic pathway, which is the way plants and fungi make chemicals. These biosynthetic pathways can be transferred to yeast and other organisms. The role of producing these medicinal chemicals is taken over by yeast cell factories, which reduces the need for wild species to be harvested. This method has been successfully used to increase artemisinin yields.
Kew houses specimens from all over the globe in its seed banks. They discover and preserve new species by studying plant and fungi DNA. They examine the threat level of species to determine if they should be added to the IUCN Red List of Endangered Species. This guideline guides conservation strategies as well as policy. Kew raises awareness about the importance of plant life in biodiversity hotspots like the tropics and influences national authorities to prioritize the protection of plants as well as their habitats.
AI and citizen scientists help to identify species with apps. A free-of-cost genetic database, which aims at sequencing the genomes of all living things on Earth, is also available.
Future opportunities for discovery of new molecules from nature are possible thanks to advances in science and technology. There are also a variety of pathways that can be used to synthesize them and more sustainable sources. This report, written by Howes and Quave, and other scientists around the world, is a reflection on potential solutions to global health problems.
Biodiversity refers to all life on Earth in all of its many interactions and in all its forms. Quave wrote about the potential for plants to make future antibiotics.
