Study confirms anti-inflammatory property of traditional Samoan remedy

  • Aided by traditional Samoan healers, researchers isolated the bioactive compounds from the leaves of a small, tropical tree called Psychotria insularum.
  • The leaf extract, along with the isolated compounds, was recently discovered to prevent the production of inflammatory molecules in immune cells as well as ibuprofen did.
  • Despite opinions that Indigenous knowledge is merely superstitious, Samoan researchers say it is the product of centuries of empirical testing, careful observation and the conservation of their natural resources.
  • Researchers and Samoan traditional healers have set up gardens to protect traditional medicinal plants with therapeutic potential from the impacts of climate change and environmental destruction.

Taking a pill is what gets many people around the world through physical pain or other forms of ill health. Many others took to more traditional plant-based remedies for their benefits. While concoctions using leaf and bark extracts may not be stamped with a pharmaceutical company logo, they may be just as effective at treating some conditions as their lab-manufactured counterparts.

Scientists from Samoa, New Zealand and the United States isolated and characterized the active compounds in Psychotria insularum, a small tropical tree whose leaves have been used for centuries in a traditional Samoan remedy called matalafi. They found that chemicals in matalafi have potent anti-inflammatory properties, according to a recent report published in the Proceedings of the National Academy of Sciences (PNAS).

Lead author and native Samoan Seeseei Molimau-Samasoni started the work in 2013 as part of her dissertation, fueled by government efforts to reignite research in Samoan natural products and medicine. Molimau-Samasoni, now a biologist at the Scientific Research Organization of Samoa (SROS), says she was primarily interested in identifying the biomedical basis behind natural Samoan medicines, as well as learning whether there was a link between a remedy’s traditional use and its molecular activity.

“We have hundreds and hundreds of medicinal plants recorded in various publications on Samoan traditional medicines,” Molimau-Samasoni says. So she first had to whittle down the list to something manageable. Due to the type of molecular screening system she used in her lab, she focused her research on plants that were used for antimicrobial reasons, such as treating skin wounds or infections.

Medicinal plants
Medicinal plants being studies at the Scientific Research Organization of Samoa’s (SROS) medicinal garden. Image courtesy of Seeseei Molimau-Samasoni.

She also wanted to ensure that she didn’t kill any of the plants she harvested for her research. Healers might use the leaves, bark, roots, berries, or blossoms of a plant, she says, but she decided to restrict her options to just plants whose leaves were used in remedies, further narrowing her list down to 11 medicinal plants. After a botanist and traditional Samoan healers helped her identify the plants, Molimau-Samasoni harvested the leaves and took them to New Zealand for analysis.

Of the 11 remedies, matalafi had the most clearly potent effect. Surprisingly, “it was also the plant that I was most skeptical about,” Molimau-Samasoni adds, laughing.

“When I talk about matalafi,” she says, “the first thing that comes to mind is the superstitious belief surrounding [it].” Matalafi is known for treating illnesses attributed to ghosts or spirits, known as aitu, she says, although it’s also used to treat various infections and inflammation. She says in Samoan, the plant’s name translates to “hide from sight,” and there’s a superstition that if you announce you’re going out looking for it, it will hide from you. Just to stay on the safe side, they decided in advance to collect the leaves from plants growing in a villager’s garden.

Over the next eight years, Molimau-Samasoni, along with collaborators from Victoria University of Wellington in New Zealand, Stanford University and New York University in the U.S., and the Samoan Ministry of Natural Resources and Environment found that matalafi chelates, or traps, iron within cells. They later isolated the two main compounds responsible: rutin and nicotiflorin. When they treated immune cells from mice with either rutin, juice from P. insularum leaves, or ibuprofen, they found that matalafi and rutin reduced the production of inflammatory molecules called cytokines to a similar extent as ibuprofen. That suggested that the centuries-old remedy may hold modern therapeutic potential.

“I was very impressed,” says Gaugau Tavana, a Samoan chief and educator who was not involved with the study. Tavana is a learning specialist at the Student Athlete Life and Learning Center at Brigham Young University (BYU) and also teaches Samoan language and culture classes.

Hopefully, he says, matalafi will become a new remedy for certain future diseases. Tavana notes the approach of collaborating with local healers to identify plant-based remedies was the same strategy his long-term collaborator Paul Alan Cox, an ethnobotanist, used to discover the anti-HIV drug prostratin.

So far, matalafi’s future is looking bright. “Ever since this paper has come out,” Molimau-Samasoni says, “we’ve received a lot of interest from around the world in terms of research collaborations.” She says people are interested in using it to treat iron overload, including in conditions such as Alzheimer’s disease and Parkinson’s disease, or for treating pain. Using structural biology and computational analysis, other researchers have predicted that rutin may even be able to inhibit replication of SARS-CoV-2, the virus that causes COVID-19.

“We’re very excited that this paper has provided scientific merit for traditional Samoan medicine,” Molimau-Samasoni says. “We’re hoping that our research will continue to provide scientific background and molecular basis for how our plants are being used in traditional medicines.”

‘Scientists in their own right’

Tavana says many scientists don’t consider Indigenous wisdom to be credible, noting that his and Cox’s work rooted in traditional teachings has been dismissed in the scientific world as merely folklore.

While Indigenous remedies are steeped in culture and have been in practice for centuries, Molimau-Samasoni says not all of them were pulled from thin air. “These people didn’t just sit around and think, ‘Oh, well, we’ll try that leaf,’” she says. They spent years of trial and error, testing the best combinations of plants and preparation methods to empirically determine the best treatments.

Tavana adds that healers keep experimenting throughout their lives to optimize remedies. He recalls how his own grandmother, a traditional healer in his village of Saipipi in Samoa, was exquisitely precise when preparing traditional cures, sending him in search of exact numbers of leaves or berries for the treatment she was preparing.

Medicinal plant in Samoa
Calophyllum inophyllum is a plant found in the Polynesian islands. Its crushed leaves are used to treat rashes in a traditional Samoan medicine called ‘fetau’. Image courtesy of David Eickhoff/Flickr.

“They are scientists in their own right,” he says.

In addition, Tavana says Samoan culture emphasizes the importance of observation, often considered the first step in the scientific method. He says that while there is little formal structure for passing traditional teachings from generation to generation, the elders will tell the younger people, “Look — there are only two things you need: One is you use your eyes properly, and look,’” he says. “And then your ears, to hear what is being said.”

He recalls watching elders in his village make incredibly accurate predictions about when certain fish species will arrive or what will happen with the weather. “They look at the weather, they look at the ocean, the sun and the moon and the sky,” Tavana says, all of which enable them to predict the fish’s arrival to the exact day.

With such a rich source of knowledge, researchers are currently questioning how they can learn from Indigenous sources in an ethical manner.

Tavana says many Samoans are sensitive to researchers coming in from other places, particularly if their research ties into the culture itself. He notes there’s been a history of researchers not sharing the discoveries they’ve made with the Samoans who supported their research, while others have misrepresented Samoan traditions and customs to the academic world.

Even Molimau-Samasoni says she was met with some skepticism when trying to engage healers outside her own village when she started her research nearly a decade ago. “They didn’t want their bread and butter to be put under the microscope,” she says. “They didn’t want scientists coming in and saying, ‘Actually, your traditional medicine does not work.’”

But now, she says, they’re keen to share their knowledge and collaborate with researchers, in part due to government initiatives implementing policies that ensure traditional healers and researchers work hand in hand with fair resource and benefit sharing.

Tavana adds that he and Cox’s groups have included their Indigenous collaborators as co-authors and patents, and have translated the abstracts of their publications into Samoan so their research will be accessible.

In addition to improving collaboration between researchers and healers, Molimau-Samasoni says she and her colleagues are setting up digital databases for traditional healers to access and share their knowledge so that it isn’t lost.

Culture and conservation tightly bound

But it’s not just knowledge that needs to be conserved. The connection between Indigenous Samoan wisdom and the natural world is deep, and as such, “if you lose the environment,” Tavana says, “you lose the culture.” If medicinal plants are lost to habitat destruction and climate change, the practical application of centuries of experimentation will fade. Additionally, any untapped pharmaceutical potential these plants have that could be discovered by combining Indigenous knowledge with cutting-edge molecular analysis could also be lost.

The Scientific Research Organization of Samoa’s (SROS) medicinal garden. Image courtesy of Seeseei Molimau-Samasoni.

Despite having their own ways of sustainably managing their natural resources, Tavana says Samoans are still threatened by climate change and environmental destruction. “You can do so much to preserve and conserve the island environment,” he says, “but there are still other factors that come into play.” In the face of this, he says, Samoans are doing what they can to preserve the biodiversity that plays such a huge role in their traditional ways of life.

According to Molimau-Samasoni, when she and her colleagues were looking for medicinal plants for their research, they realized that some were becoming harder to find. This prompted SROS to establish a garden of medicinal plants, ensuring “that we will always have the plants that are currently available to us, and that they are protected,” she says.

The garden protects tried-and-true remedies like matalafi along with other medicinal plants that may have as-yet-undiscovered therapeutic potential.

Back in Tavana’s village, the locals are also creating a garden of native and medicinal plants, as well as establishing a new building dedicated to conserving both the culture and the environment. Tavana leads a group of BYU students to Samoa to assist in conservation projects such as coral reef restoration. But ultimately, he says, the villagers have ownership of the project, trusting them to know the best way to protect their natural resources.

“The conservation project belongs to them,” he says. “The ideas originate from them, and we’re there to support that.” 

Banner image: The Scientific Research Organization of Samoa’s (SROS) medicinal garden. Image courtesy of Seeseei Molimau-Samasoni.


Molimau-Samasoni, S., Woolner, V. H., Foliga, S. T., Robichon, K., Patel, V., Andreassend, S. K., … Munkacsi, A. B. (2021). Functional genomics and metabolomics advance the ethnobotany of the Samoan traditional medicine “matalafi.” Proceedings of the National Academy of Sciences, 118(45), e2100880118. doi:10.1073/pnas.2100880118

Annie Melchor is freelance science writer based in the Bay Area. Follow her on Twitter at @sjmelchor.

Related listening from Mongabay’s podcast: A look at two stories that illustrate how bioacoustics are helping to advance Indigenous-led conservation initiatives. Listen here:

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