Aspirin, morphine and chemotherapy: the essential medicines powered by plants

People and the natural world are inextricably interlinked. It's been scientifically proven that spending time outside is good for our physical and mental wellbeing, but nature can also literally save our lives. Today, some of the biggest killers in the western world, including cancer and heart disease, can be cured using medicines derived from plants.

Herbal remedies and traditional medicines are used by millions of people around the world. Chamomile can make us feel soothed and relaxed, while ginger can boost digestion and echinacea is thought to support the immune system. Medicinal herbs, leaves and roots are used to prevent and treat common ailments from colds and anxiety to nausea and skin ailments.

Today, around 11% of the drugs considered 'basic' and 'essential' by the World Health Organisation originated in flowering plants - and there are many more from those without flowers. Thanks to decades of research, we're able to harness the lifesaving powers of superhero plants whose chemical compounds form the basis of powerful drugs that can help combat cancer, Parkinson's disease and malaria.

Humans have been using plants to heal since before we developed a written language. Ancient civilisations created concoctions of seeds, herbs, leaves, fruit and bark to treat a wide variety of illnesses. The use of traditional Chinese medicine dates back thousands of years, while 5,000-year-old clay slabs from Nagpur in central India are early written evidence of people using plants such as poppies and mandrakes as drugs.

An ancient Egyptian scroll that has been dated to about 1,500BC recorded the medicines of the day. The Ebers Papyrus, as it is known, recommends heated herbs for asthma, mint and sandalwood to aid healthy digestion, and juniper for chest pains. While some of its recommendations are questionable by modern standards, others still hold true today. For instance, it advocates the use of aloe vera, which is still applied to burns and ulcers, and honey, which is valued for its natural antibacterial properties.

Natural inspiration

Usually, any drug derived from plants prescribed by a medical professional has gone through years of rigorous testing for efficacy and safety before being approved. In the western world, new medicines are usually designed by chemists and biologists using computer models - but they still turn to the natural world for inspiration.

Plants are an abundant source of potential new medicines and often serve as chemical templates for the design of novel drugs to treat humanity's most serious ailments. We're finding new candidate plants all the time. Researchers then spend months and years isolating their active ingredients and reproducing them in a lab.

At some point in our lifetimes, most of us have taken pain management drugs derived from specialist plants. The humble aspirin is a modern miracle medicine and one of the most widely used drugs in the world. It's extracted from the bark of the willow tree, which was recommended for the treatment of aches and pains by the ancient Egyptians in the Ebers Papyrus. People used to chew twigs to alleviate pain and it's still possible to buy willow bark for this purpose.

However, most of us take over-the-counter aspirin pills in which the active ingredient - salicylic acid - has been replicated synthetically. Aspirin has been shown to reduce the risk of heart attack and even be beneficial in the fight against cancer; experts believe it probably has even more benefits that have yet to be discovered.

Pain relieving plants

Morphine, a strong painkiller commonly prescribed after surgery or for broken bones, is an extract of the opium poppy that, today, is synthesised in labs. Opium (morphine) was first isolated from poppies by pharmacist Friedrich Serturner in the early nineteenth century, before pharmaceutical chemistry was recognised as a science.

At the time, the drug was taken orally (whereas today it is usually administered intravenously) and Serturner experimented on both himself and his volunteers to find a safe dose. Like opium, many of the plants we use to treat illnesses are toxic and must be taken in carefully measured non-lethal doses.

Heroin, another derivative of the opium poppy, was first synthesised for medical use before its potent addictive properties were recognised. Each year it is responsible for thousands of deaths due to overdosing. It's partly thanks to Serturner and his peers that we know so much about plant chemistry and biology, and are able to learn even more from nature. The discovery of morphine paved the way for a new branch of chemistry, and also led to the discovery of codeine (a medium-strength painkiller also derived from opium poppies) and quinine (a bitter compound from the bark of the tropical Cinchona tree that’s used to treat malaria). Modern scientists build on the work of these early researchers.

Today, plants are helping to cure some of the world's deadliest diseases. According to the World Health Organisation, globally the most common causes of death are heart disease, stroke, chronic obstructive pulmonary disease, respiratory infections and Alzheimer diseases and other dementias. Diarrhoeal diseases, cancer and diabetes are also big killers. There are treatments that were originally derived from nature available for almost all of them.

Plants could also contribute to end-of-life care in the future. Medicinal herbs are being studied that could support patients with Parkinson's disease, a brain disorder that affects upwards of 10 million people. 

Water hyssop, Bacopa monnieri, is a tropical aquatic plant that has been used for centuries in India and China to support brain function. It's now being investigated by researchers at Jawaharlal Nehru University in New Delhi as a way of reducing inflammation in the brain, and possibly enhancing cognitive performance in elderly people, protecting the brain from decline in old age.

Snowdrops, Galanthus nivalis, are loved in the UK for being among the first flowers to bloom in early spring. However, they are poisonous if eaten and there is evidence the ancient Greeks used them, in small doses, for their mind-altering effects.

In the 1950s, a natural alkaloid called galantamine was extracted from snowdrop bulbs, and this is now used to slow the progression of Alzheimer's disease and mitigate its symptoms, such as memory loss, though it cannot cure the disease. It works by slowing the decline in the transmission of chemical messages in the brain. Proteins from snowdrops are also being investigated as a possible treatment for HIV.

Overharvesting of the bulbs that produce these delicate drooping flowers for our gardens and medicinal use has resulted in many species becoming threatened in the wild.

Galantamine is also found in the relatives of snowdrops, such as daffodils. Botanist Dr Mark Carine explains in the video below.

Genetic engineering

Researchers are studying how plants can be genetically modified to create new medicines. Transgenic plants have been engineered to introduce novel beneficial traits and biologists are exploring whether they can be used to mass-produce pharmaceutical products.

One contender is the tobacco plant. The smoking of tobacco has become one of the biggest public health threats the world has ever encountered, and cigarettes kill more than eight million people a year. Paradoxically, in the future, tobacco may become the primary weapon against one of the world's deadliest diseases and could be used to save millions of lives. 

Tobacco plants are easy to alter and manipulate due to their genetic makeup, so they are perfect candidates for testing new technologies. Biologists in Oklahoma are developing plants with seeds containing proteins that thin the blood, helping to fight stroke and heart disease. And as tobacco is an inexpensive, high-volume crop that's already grown worldwide, this could be a sustainable and low-cost way to produce new complex medicines.

Cancer-fighting flowers

When it comes to treating cancer and its symptoms, the natural world has given us dozens of helpful ingredients that could help save millions of lives.

Childhood leukaemia is treated with drugs derived from the Madagascar periwinkle, Catharanthus roseus, a decorative herb native to the island of Madagascar. The Indigenous People of the island traditionally use the plant to treat diabetes. When western researchers were investigating its chemical properties in the 1950s, they realised that extracts from the plant contained chemicals with anti-cancer properties.

The discovery has given us two closely related drugs, vincristine and vinblastine, which can kill cells that are rapidly dividing, like cancer cells. Synthesis of these chemicals is complex and still not fully understood by scientists so, since the 1950s, doctors have been relying on crops of the plant itself to treat these deadly diseases. It takes about 500 kilograms of dried leaves to produce one gram of vinblastine.

In 2018, scientists at the John Innes Centre, a research institute in Norwich, finally sequenced the full genome of the Madagascar periwinkle and identified the enzymes that build vinblastine. This should pave the way for a synthetic version of the drug, allowing more people to benefit from its life-saving properties.

It's only by knowing about nature that we can use it in new and sophisticated ways, which is why research on new species is so important. Experts at the Museum play a big part in helping to categorise life on Earth, including new plants and animals that are still being scientifically discovered.

Understanding their relationships to each other helps pharmacologists know where to look in their quest for new treatments, so it's never been more urgent or more important that we continue our work to document and understand the diversity of life on our planet.