Managing diabetes with medicinal plants

Blog team: 
Peter Giovannini


The diabetes pandemic

The prevalence of diabetes has been increasing worldwide, especially in Middle Income Countries (MICs) where access to the healthcare needed for its prevention and treatment is often limited.

The World Health Organisation (WHO) recently published a Global Report on Diabetes, which highlighted that the global prevalence of diabetes (currently 8.5% for both type one and type two diabetes) nearly doubled between 1980 and 2014. 

Diabetes has a considerable impact on the health of individuals, national economies and society as a whole. In 2012 diabetes and high blood glucose caused 3.7 million deaths, and cost an estimated 827 billion US dollars globally. Cost-effective solutions to prevent and manage diabetes are therefore needed urgently.

Local use of medicinal plants: type two diabetes

Several ethnobotanical studies have reported the local use of plants to manage type two diabetes. In many instances, these studies were conducted among indigenous people, who have a particularly high incidence of diabetes, and often lack access to conventional healthcare. This raises the question of whether scientific evidence supports the use of these plants to manage diabetes, and if such herbal medicines could be better integrated into health care systems.

Medicinal plants to manage diabetes in Central America

In a recent study we aimed to determine which herbal remedies are traditionally and currently used to manage diabetes in Central America, and to what extent scientific evidence supports their local use. The population of Central America, which includes a large indigenous population, has a strong tradition of using herbal remedies. The total prevalence of diabetes in the region is currently 8.5%. This figure is likely to increase due to the high percentage of young people in the population, because the risk of developing the disease increases significantly with age.

Map of Central America (CIA / Public Domain).

We started by conducting a literature review of previous studies on medicinal plants in Central America (Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua and Panama; all middle-income countries according to the World Bank definition). From this, we compiled information on species used to manage diabetes or conditions that may arise from diabetes, creating a database. Importantly, we also noted which plant parts were used medicinally, because the uses and properties for different parts of the plants may vary. 

We then looked into whether there was any scientific basis that might explain the local uses of the selected plant species. We did this by searching literature for information on plant chemistry, pharmacology, and clinical studies investigating their medicinal uses in humans.

More than 100 species used to manage diabetes in Central America

We found 104 plant species used to manage diabetes in Central America but only seven of these species were reported independently in at least three different studies. These seven species were: Momordica charantia L., Neurolaena lobata (L.) R. Br. ex Cass, Tecoma stans (L.) Juss ex Kunth, Persea americana Mill., Psidium guajava L., Anacardium occidentale L., and Hamelia patens Jacq. 

We also found that several species used to manage diabetes were also used to treat conditions that may develop as a consequence of diabetes. For example, there are reports on the traditional use of M. charantia for kidney and skin conditions that may be associated with diabetes.

Momordica charantia L. Several studies conducted among different ethnic groups reported the use of the leaves and stems to prepare herbal remedies to manage diabetes (Image: H. Zell CC by-SA 3.0).

Available pharmacological studies provide some rationale to explain the local uses of M. charantia L. For example, some laboratory tests showed that extracts, including phytochemicals (triterpenoids) from the fruit and stems, may lower blood glucose.

However, more extensive and robust scientific studies are needed to further understand the traditional and potential uses of medicinal plants and their constituent phytochemicals. In particular, clinical trials in humans are needed, using standardised plant extracts that contain known levels of the most relevant phytochemicals.

Towards the 2030 sustainable development agenda

The 2030 Agenda for Sustainable Development lists targets that include achieving universal health coverage and providing access to affordable essential medicines (SDA 2030 Goal 3). Medicinal plants currently play an important role in meeting the health care needs of many people around the world. According to WHO, up to 80% of the population in some regions of the world use traditional medicines for health care. There may still be a large untapped potential to increase the sustainable use of medicinal plants to provide cost-effective medicines.

United Nations Sustainable Development Goals adopted by the General Assembly and promoted by the UN.

Our review of medicinal plants used for managing diabetes in Central America shows that medicinal plants are currently contributing to the provision of low cost and culturally appropriate health care in this region. It is also important, however, to gain a better understanding of their effectiveness and safety, and to be able to fully understand their potential as part of a cost-effective and sustainable approach to healthcare.

- Peter -


Giovannini, P., Howes, M.-J.R. & Edwards, S. (2016). Medicinal plants used in the management of diabetes and its sequelae in Central America: a review. Journal of Ethnopharmacology 184, 58 – 71. Available online

Kew goes to the Flora Malesiana 10 symposium

Blog team: 
Tim Utteridge

Malesian subkingdom: boundaries and regions of the Malesian floral subkingdom (Map: © Encyclopædia Britannica Online).

What is Malesia?

Recently (11–15 July 2016) the Royal Botanic Garden Edinburgh hosted the 10th Flora Malesiana symposium – an important meeting bringing together scientists working on the taxonomy, systematics and conservation of the plants and habitats of South-East Asia. Malesia is a phytogeographic area that includes all the countries from Malaysia through to Papua New Guinea. A phytogeographic area is determined by the distribution of plant species within the area, and the influence of these plants on the earth's surface. Malesia can be broadly split down the middle by Wallace’s Line into Sunda in the west, with lowland forest dominated by the emblematic Dipterocarpaceae, and the more poorly known Sahul region in the east which includes New Guinea with forests not dominated by a single plant group.

Kali Kopi river, lowland Indonesian New Guinea (Image: T. Utteridge).

Classify, cultivate and conserve

The conference theme was ‘Classify, Cultivate and Conserve’, reflecting the activities taking place at institutions both in and outside the region. The Flora Malesiana (FM) aims to publish a Flora of the region, and many presentations highlighted new research findings helping to classify the massive species diversity found there. The conference also showcased horticulture and conservation activities, from the excellent Ericaceae programme at Edinburgh to the massive expansion of the botanic garden network through Indonesia, and the red-listing work done in Malaysia on the Malaysian Dipterocarpaceae.

Imbak River, lowland dipterocarp forest, Sabah (Image: T. Utteridge).

There were over 180 participants with many delegates from the region. Kew was well represented by 13 staff and HRFs/HRAs (Honorary Research Fellows/Associates)* involved in 16 contributions (including 6 oral presentations and 6 posters presented) covering topics from alpha taxonomy and floristics, to conservation and molecular phylogenetics.

Kew in Malesia

Kew has several ongoing programmes in Malesia, and particularly relevant to the FM project is the soon-to-be published account of the Lamiaceae (tropical mints) which Dr Gemma Bramley coordinated from Kew. Taxonomically, we are also involved in working on several ecologically important and/or species-rich groups such as Orchidaceae, Saurauia (kiwi fruits), Urticaceae (nettles), Gesneriaceae (African violet relatives), Primulaceae, Myrtaceae and Palmae, amongst others.

We have a research focus on the biodiversity and conservation of New Guinea but it became apparent from many of the talks that our understanding of SE Asia is grounded in ecological work undertaken in the western part of the region, in lowland dipterocarp forest. The same patterns may not be applicable to the eastern part of Malesia but currently we have little data to work from.

Kew’s Tropical Important Plant Areas (TIPA) programme will also benefit from taxonomic and ecological data generated from our work in Malesia, as Indonesia New Guinea is one of the named countries in the output.

The Board of the Flora Malesiana Foundation is tasked with steering the project and overseeing activities contributing to the Flora, especially linking botanists to family accounts that have yet to be published. Kew is represented by Timothy Utteridge, and it was decided at this meeting to have some of the activities undertaken at Singapore Botanic Gardens. This gives the Flora Malesiana project even more regional representation (the Chair is held by Indonesia).

Board of Foundation, Flora Malesiana.

(L to R): Leng Guan Saw (FRIM HRF, formerly Director of Biodiversity Division, Malaysia), Peter Wilkie (Chair of FM10 Committee, RBGE), David Middleton (Director/Research and Conservation & Keeper of the Herbarium, Singapore Botanic Gardens), Dedy Darnaedi (LIPI, Indonesia), Daniel Thomas (FM Secretariat, SBG), Maribel Agoo (De La Salle University, Philippines), David Mabberley (Adjunct Professor, Macquarie University Sydney), Joeni Siti Rahajoe (Head of Botany Division, LIPI, Indonesia), Daniele Cicuzza (University of Brunei Darussalam); Eric Smets (Director of Science, Naturalis), Marco Roos (FM Secretariat, Naturalis), Charlie Heatubun (Professor of Forest Botany, Universitas Papua, Indonesia and Kew HRA) and Timothy Utteridge (RBG Kew).

Kew and Singapore are actively working on a range of projects whilst developing new ideas, under the auspices of the recently signed MoU (memorandum of understanding). They are in the final stages of negotiating an MoU with LIPI (Indonesian Academy of Sciences) in Indonesia.

The conference was very successful, with many new links made with key regional stakeholders, and existing relationships were strengthened. Kew staff who attended would like to thank the organisers (particularly Peter Wilkie), as well as the Bentham-Moxon Trust for support towards costs. The meeting is held every three years, and the next meeting will be held in Borneo (Sarawak or Brunei).

- Tim -

Group photograph on the opening day in the RBGE lecture theatre (Image: Royal Botanic Garden Edinburgh).

For more details on Flora Malesiana 10 (abstracts etc.) or work in Malesia please feel free to contact Tim Utteridge or any of the Kew attendees listed below.

*Peter Ashton (HRF), Gemma Bramley, Marie Briggs, Rodrigo Camara Leret, Helen Chadburn, Ruth Clark, Mark Coode (HRF), Eve Lucas, Alison Moore, Siti Munirah (HRA), Lisa Pokorny, Andre Schuiteman, Timothy Utteridge and Brian Yap.

Madagascar's orphans of extinction

Blog team: 
Wolfgang Stuppy & Aurélie Albert-Daviaud


The island of Madagascar is one of the world's top biodiversity hotspots. Its landmass separated from continental Africa 160 million years ago, and from India 88 million years ago, well before the demise of the dinosaurs. Due to its long geographical isolation it has become home to a unique fauna and flora. Over 80% of the island's plants and animals are endemic, which means they are found nowhere else on Earth.

Artist’s impression of elephant birds on a beach in Madagascar (Painting © Velizar Simeonovski).

The riddle of the rotting fruit

Madagascar is, in many ways, a unique place. One peculiar aspect of its biodiversity is that, compared to other tropical areas, it has relatively few fruit-eating (and therefore seed-dispersing) animals. Among all animals worldwide, birds are by far the most important dispersers of seeds. However, Madagascar is poor in frugivorous (fruit-eating) birds. In fact, there are only five bird species on the island which can be considered bona fide dispersers rather than granivores (seed-eaters). This dispersal-ecological gap is filled by lemurs, Madagascar's unique primates. Of the c.100 extant lemur species, 21 are frugivores and therefore ‘good’ seed dispersers.

Many of Madagascar's endemic plant species produce fleshy fruits which are obviously animal-dispersed but their seeds are too large to fit the gape of any living animal. As a result, these fruits find no 'takers' and simply drop to the ground in large numbers where they rot.

Despite containing delicious sweet pulp, the tennis ball sized fruits of a Strychnos species in Madagascar rot under the tree (Image: W. Stuppy).

Madagascar’s lost megafauna

The only logical explanation for the apparently paradoxical existence of fleshy fruits with no dispersers is that they are adapted to larger animals that no longer exist.

Indeed, over the last 2,000 years, the island of Madagascar has lost 48 unique species of large-bodied animals. Among them were aardvark-like insectivores (Plesiorycteropus madagascariensis), giant lemurs, pygmy hippopotamuses, giant tortoises and, probably the most famous of all, around eight species of gigantic ratites (Aepyornithidae), the so-called elephant birds (Aepyornis spp., Mullerornis spp.).

The last historical sighting of an elephant bird was in the 17th century. Since their extinction, the role of the largest seed dispersers has passed from the elephant birds (450kg) to the radiated tortoise (10kg) (Hansen & Galetti, 2009).

The most important seed dispersers among Madagascar’s extinct animals were undoubtedly the giant lemurs; there were 17 species, all significantly larger than any extant lemur species. It is likely that more than half of these giant lemurs had a diet of fruits or a mixed diet of fruits and leaves. Therefore, they are extremely likely to have acted as seed dispersers.

As a result of the disappearance of these large-bodied animals, large-seeded plants that relied on them have now lost their dispersers. The fruits have become ‘anachronistic’, a concept first suggested by Janzen & Martin (1982). The plants themselves have become 'orphans' of extinction and this means that they will most likely face the same fate as their animal partners.

Many of Madagascar’s extinct giant lemurs were important seed dispersers capable of swallowing very large seeds (Images: © Smokeybjb – Wikipedia/Creative Commons Licence).

Why is seed dispersal so important?

Seed dispersal is a key process in plant communities that allows seeds to escape direct competition with both their parent plants and their siblings. Seed dispersal reduces density-dependent mortality of seeds and seedlings, and it allows population growth as well as gene flow between populations.

Non-dispersal or impaired dispersal leads to reduced geographic ranges and restricted gene flow between populations. The result is diminished genetic diversity within populations which ultimately reduces individual fitness. Although it is a slow process, it has been demonstrated that the loss of animal seed dispersers considerably increases the risk of extinction for plants with animal-dispersed fruits or seeds.

Finding Madagascar’s orphans of extinction

Several Malagasy plants with fleshy fruits and excessively large seeds have long been suspected to be anachronistic. Their seeds are simply too large to be swallowed by any extant disperser.

Among these plants are the famous baobabs (Adansonia spp., Malvaceae), several palm species (Borassus madagascariensis, Hyphaene coriacea, Orania longisquama and Satranala decussilvae) and two species of the genus Dilobeia (Proteaceae) (Baum, 1995; Dransfield & Beentje, 1995; Godfrey et al., 2008). However, these are just the most obvious cases; there are many more waiting to be identified.

Because Madagascar’s orphans of extinction potentially share the same fate as their lost animal partners, we have started a research project which aims to identify, study and conserve species whose fruits have become anachronistic.

Orphans of extinction: clockwise from top left: fruits of baobab (Adansonia grandididieri, Malvaceae); Borassus madagascariensis; Satranala decussilvae; Hyphaene coriacea (Arecaceae) (Images: W. Stuppy, R. P. Bayton, J. Dransfield).

Size does matter

The simplest way to initially identify suspected dispersal anachronisms is via the size of the seeds. If the seeds of an obviously animal-dispersed fruit are too large to be swallowed by any extant disperser, they are very likely to be anachronistic.

In a recently published paper (Federman, et al. 2016) the authors calculated the absolute maximum seed sizes that extinct and extant lemurs could/can swallow based on the relationship between body mass and maximum ingestible food size. They found that among extant lemurs, the black-and-white ruffed lemur (Varecia variegata) and the red ruffed lemur (Varecia rubra) are the two species that can swallow the largest seeds, limited to a diameter of up to 26 mm. However, among the extinct giant lemurs, the largest disperser, Palaeopropithecus ingens (a sloth lemur), could probably swallow seeds of up to 70 mm in diameter (e.g. Borassus madagascariensis) – nearly three times larger.

The logical conclusion is that any plant species in Madagascar that has animal dispersed fruits with seeds larger than 26 mm in diameter is now anachronistic.

Black-and-white ruffed lemur (Varecia variegata); and red ruffed lemur (Varecia rubra) (Images: © Paul Reynolds, © Hans Hillewaert, Wikipedia/Creative Commons Licence).

Found on a recent field trip in March: seeds and fruits too large for any extant disperser. Left: Salacia sp. (Celastraceae), right: Symphonia sp. (Clusiaceae) (Image: W. Stuppy).

What this means for conservation

Extreme dispersal anachronisms, i.e. cases where no extant animal species is capable of swallowing (and therefore dispersing) the seeds, are the most compelling cases. However, anachronism is not simply a binary concept. Lesser dispersal inefficiencies also qualify as anachronisms. For example, the black-and-white ruffed lemur and the red ruffed lemur are the only extant species able to facilitate the dispersal of many large-seeded species which were undoubtedly also part of the diet of the extinct giant lemurs. However, both species are currently critically endangered and are irreplaceable in their seed dispersal function. If they also perish, yet more of Madagascar’s unique plant species will face an uncertain future.

Identifying and studying Madagascar’s orphans of extinction is an important and urgent task. Species that have lost most if not all their animal dispersers are on borrowed time. The results of our research will hopefully inform and improve conservation strategies and policies, which should lead to a more secure future of Madagascar’s diverse forests.

- Wolfgang & Aurélie -


We would like to thank our Kew colleagues Gwilym Lewis, Bill Baker, Stuart Cable and Wolf Eiserhardt for their collaboration, and our Kew MSc student Sarah Perillo for her work on anachronisms in Madagascan palms. We also thank the team of the Kew Madagascar Conservation Centre (KMCC) for their invaluable collaboration, in particular Hélène Ralimanana, Franck Rakotonasolo, Guy Onjalalaina, Romer Rabarijaona and Tatamo Andrianantenaina. Without their input, ranging from obtaining permits to organising field work and their excellent plant identification skills, this project would not be possible.

This project is part-funded by the Joseph Jones and Daisy and Graham Rattenbury Charitable Trust.


Baum, D. (1995). A systematic revision of Adansonia (Bombacaceae). Annals of the Missouri Botanical Garden 82: 440-470.

Dransfield, J. & Beentje, H. (1995). The Palms of Madagascar. Kew: Royal Botanic Gardens, Kew and International Palm Society.

Federman, S., Dornburg, A., Daly, D.C., Downie, A., Perry, G.H., Yoder, A.D., Sargis, E.J., Richard, A.F., Donoghue, M.J. & Baden, A.L. (2016). Implications of lemuriform extinctions for the Malagasy flora. Proceedings of the National Academy of Sciences Early Edition. Available online

Godfrey, L.R., Jungers, W.L., Schwartz, G.T., & Irwin, M.T. (2008). Ghosts and orphans. In: Elwyn Simons: a search for origins, ed. J.G. Fleagle &C.C. Gilbert, pp 361-395. Springer, United States. Available online

Hansen, D.M. & Galetti, M. (2009). The forgotten megafauna. Science 324: 42-43. Available online

Janzen, D.H. & Martin, P.S. (1982). Neotropical anachronisms: the fruits the gomphotheres ate. Science 215: 19-27. Available online

Gifts in Wills Information Tour: Economic Botany - how are plants used by people?

Event details

Wednesday 18 October

Joseph Banks Building, Kew Gardens


Free. Booking is essential. Please call 020 8332 3249 or email at least one week in advance. 

Event overview

Food, medicines, attributes of culture – Kew’s Economic Botany Collection is an extraordinary resource of artefacts from the across the globe and represents various uses for plants, spanning over 100 years.

Join this tour to discover some of the most fascinating objects hidden behind the scenes and learn how you can help Kew identify and research the potential of plants and fungi for human use with a gift in your Will.

Booking is essential. Please call 020 8332 3249 or email at least one week in advance. 

Find out more about legacies at Kew, and watch our new film featuring Kew’s supporters.

Find out more about the Economic Botany Collection at Kew.


October half-term fun

Event details

23 to 27 October, 11am to 3pm



Included with entry to Wakehurst

Event overview

Storm survivors

Commemorate the 30th anniversary of the Great Storm of 1987 and discover Wakehurst’s oldest trees.

Activities include arts and crafts, games, fun facts and a trail.

Wild play at Wakehurst

Don’t forget to pay one of your last visits to the Children’s Heritage Garden – it closes for the winter on 29 October.

Young visitors will love hanging out in the potting shed and planting broad bean seeds. They will also adore the Mud Kitchen where they can have fun with tree and leaf-shaped cookie cutters.

The ‘dig it’ area is also always a bit hit. They can dig for wooden vegetables and replant them to their hearts content!

Kew Science Festival at Wakehurst – science goes wild!

Event details

22 to 23 July, 10am to 5pm



Included with entry to Wakehurst

Event overview

Don your lab coat and dig out your goggles for Kew’s Science Festival at Wakehurst.  Join in with fantastic workshops, shows, tours and hands-on experiments that will inspire children and adults alike.

All budding scientists are invited to make some discoveries, with researchers from both Kew Gardens and Wakehurst showcasing some amazing events and activities for all the family. Design and launch seeds in the air with the air cannon - reveal the secrets of identifying and germinating seeds - carry out brilliant botanical experiments with scientific tools.

Science fun

The Millennium Seed Bank will become the hub of the science festival, presenting a range of fun, hands-on experiments. Plus BBC TV presenter Stefan Gates will be presenting his incredible Gastronaut Live show - packed with fun food science and quirky edible delights.

Wild science

Explore Wakehurst’s beautiful wild landscape - uncover the science and conservation work all around the gardens from the crops grown on-site for research, to the conservation of rare plants and trees. Track down Charles Darwin and hear about his amazing botanical work!

Behind the scenes

Explore the Millennium Seed Bank and delve into the amazing cutting-edge research on site, with special behind the scenes science tours. Try your hand at being a researcher in the germination lab and hear from some great botanical speakers.

The Hive: Fortnightly findings

Event details

Alternate Sundays 28 May – 29 October 2017 11.30am, 12.30pm, 2pm, 3pm & 4pm

Free with entry to the Gardens

Event overview

Our fortnightly findings bringing together different community groups, national organisations and innovators to inspire you.

Meet the inventor of the Honey Flow Hive, look out for walks and talks from the British Bee Keeping Association and discover insights into city beekeeping from Bee Urban’s Barnaby Shaw.

Highlights include: 

28 May – BWARS (Bees, Wasps & Ants Recording Society) lead talks and tours on different types of solitary bees, the habitats they enjoy and what you can do to support them. 

11 June – Inventor of the Honey Flow Hive, Stuart Anderson talks about a new invention that helps make life easier for bees and beekeepers. Stuart gives a personal account of the family story behind this global crowdfunding success.

25 June – Friends of the Earth’s Great British Bee Count is underway. Join a team of citizen scientists to discover which bees are flourishing and which need our help, as part of the Great British Bee Count. 

09 July – A city that’s buzzing with Bee Urban, in London we're surrounded by flora on which bees forage; acacia trees; lavender in people's window boxes; wild honeysuckle in railway arches. All of these grow free fropm pesticides. Bee Urban give an insight into city beekeeping from their bees at home in Kennington Park to the hives they manage at the National Theatre and Southbank Centre.

23 July – BWARS (Bees, Wasps & Ants Recording Society) is back – helping us to spot and record the 26 different types of bumblebees in the UK. 

Included with entry to the Gardens. 

Save on the price of your ticket when you book online

Richmond RUNFEST

Event details

16 and 17 September 2017

Kew Gardens

Event overview

The Kew Gardens 10k is undoubtedly the most beautiful race in Europe. Experience an incredible six mile journey past the famous Palm House, Kew Palace, the great Pagoda and much more.

The course is completely flat, so has great ‘pb’ potential - or could be a perfect warm-up for the Half or Full Marathon the next day?!

For a longer distance, you can enter the Richmond Marathon or Half Marathon on Sunday 17 September. The course features many of Kew’s show-stoppers before a beautiful tour of the Thames riverside. Featuring Richmond Bridge, Teddington Lock, inside the stunning Ham House Gardens and for the Marathon course…inside Royal Hampton Court Palace.

Celebrate your achievement at an all-day family music festival just for you in Old Deer Park. FREE pint of London Pride for all runners.

This race sells out early so enter now to avoid disappointment.

Enter online



Kew Gardens 10k: Saturday 16 September 2017.

Richmond Marathon and Half Marathon: Sunday 17 September 2017.

Start location

All races start inside the Royal Botanic Gardens, Kew.

Finish location

Kew Gardens 10k finishes inside the Royal Botanic Gardens, Kew.

Richmond Marathon and Half Marathon finish a mile away in Old Deer Park (next to Pools on the Park), Richmond.