Many plants used for their healing powers in traditional medicine are related to one another, despite being found continents apart

Many plants used for their healing powers in traditional medicine around the world have been shown to be related to one another, despite being discovered continents and centuries apart.

Scientists studied over 1,500 medicinal plants from three continents and found that time and again people were independently using closely related plants to treat the same ailments. They have now drawn up a family tree covering these and 20,000 other species of plants, which they say can help identify more plants with undiscovered medicinal properties.

In one example, plants from the soapberry family are used by people in Nepal, the Cape of South Africa and New Zealand to take care of gastro-intestinal ailments. Following the results of the study the scientists have suggested that the closely related maple or lychee trees could yield clues to new modern treatments for similar medical problems.

The research is published today in the journal Proceedings of the National Academy of Sciences by scientists at the University of Reading, The Royal Botanic Gardens, Kew and Imperial College London.

The medicinal New Zealand flax (Phormium sp.). Phormium species are used traditionally by M?ori people, who call them harakeke and wharariki, to treat a wide range of conditions, including skin, respiratory and gastro-intestinal problems. Credit: Andrew Clarke, University of Warwick

The scientists say their results could enhance the success rate of companies involved in bio-prospecting, the search for new economically-valuable biomedical treatments. With tens of thousands of plant species used in medicines, identifying those likely to be of benefit is a time consuming and expensive process.

Co-author of the study, Professor Vincent Savolainen from the Department of Life Sciences at Imperial College London, who holds a joint position at the Kew Gardens, said: "This super family tree of medicinal plants will help identify new opportunities to make modern medical treatments from the active ingredients in traditional medicines and I hope that other scientists will use our study to speed up their search for innovative new treatments.

"In doing so, however, we scientists have to fulfil a duty to the people who discovered the beneficial effects of such traditional medicines. Many countries have signed up to the International Convention on Biological Diversity, which requires individuals and companies to acknowledge the origins of their discoveries. More could be done to follow this through, for example by sharing the financial benefits of a commercialised drug, or involving traditional practitioners in the development of modern medical treatments in their countries of origin."

Pseudowintera colorata, a plant species used medicinally in New Zealand. Pseudowintera species are used traditionally by M?ori people to treat skin conditions, respiratory problems, and to help heal wounds. Credit: Steven Wagstaff, Manaaki Whenua Landcare Research New Zealand.

Plants have been used in traditional medicines all around the world, although only some of which have proven medicinal benefits. This study has shown for the first time that many modern day drugs come from a few groups of closely related plants.

Co-author Dr Julie Hawkins, from the University of Reading, said: "Our study examined plants known to be used medicinally in areas unlikely to have exchanged information about medicinal properties of plants so would be using these plants after discovering them independently. It's incredibly exciting to think that communities around the world that weren't in contact with each other have sampled related plants and are using them to treat the same things."

According to the World Health Organisation approximately a quarter of modern medicines are plant-derived and many pharmaceutical drugs are derived from plants that were first used in traditional systems of medicine. For example, Paclitaxel, which is used as a chemotherapy treatment for breast cancer, derives from yew trees, while foxgloves contain a key ingredient used in cardiotonics which treat heart failure.

Dr Haris Saslis-Lagoudakis, from the Royal Botanic Gardens, Kew, who contributed to this research as part of his PhD thesis, said: "Traditional medicine has been neglected in recent years in research on the discovery of new medicinal plants and pharmaceutical drugs. It is fascinating to demonstrate that traditional knowledge that has been compiled through centuries by local communities around the globe could hold the key to curing modern-day diseases."

Saslis-Lagoudakis, HC et al. "Phylogenies reveal predictive power of traditional medicine in bioprospecting" is published in the Proceedings of the National Academy of Sciences (PNAS) DOI:10.1073/pnas.1202242109