Plant-based traditional medicines to treat Buruli ulcers

Eisman, left, in a tree that will be used in the harvesting of stem-bark. The adinkra symbols and mottoes on the bag represent strength, faith, quality, wisdom, trust and reliance and serve as words of encouragement for the trip home.

Eli Benchell Eisman, a post-doctoral research fellow working in the lab of David Sherman in the LSI and a STEM-Africa Seed Scholar, recently spent ten weeks in Ghana investigating plant-based traditional medicines in hopes of ultimately developing new drugs. 

In collaboration with Abraham Yerboah-Mensah of the Kwame University of Science and Technology in Kumasi, Ghana, Eisman collected plant samples in order to isolate, identify, and characterize compounds and ultimately work to develop these molecules into novel therapeutics.  

As a graduate student in U-M's Program in Chemical Biology, Eisman worked in the Sherman lab studying bioactive small molecules, or natural products, derived from cyanobacteria. He completed a Ph.D. in 2013. He has two bachelor’s degrees from Michigan State University, one in biochemistry and molecular biology and the other in chemistry.

What is your current work as a post-doc research fellow in the Sherman lab?

The research proposal is titled “Ethnopharmaceutical investigation of the treatment of Buruli ulcers in sub-Saharan Africa." I’m now working on the second phase of the project, which was started in Ghana.

What did you do in Ghana?

The work in Ghana was focused on identifying new molecules isolated from plants used in the herbal treatment of Buruli ulcers, a necrotizing skin fasciitis endemic to that region. The hope is that those chemicals have the potential to be developed in novel therapeutics for the disease, because right now there really aren’t any good ones. Buruli ulcers represent one of the 17 World Health Organization neglected tropical diseases. The disease is caused by infection with Mycobacterium ulcerans, a bacteria closely related to the ones that cause both tuberculosis and leprosy. One of the motivations behind the work is that like those other diseases, there aren’t any great treatments for long-term infection and there is a major social stigma associated with the ulcers, but if you catch it early and are aggressive with treatment, you can make an impact. A major component of the field work also involved community engagement and discussions with community leaders about what causes Buruli ulcers, ways to avoid transmission and education on early detection and intervention.

I was based at the Kwame Nkrumah University of Science and Technology in Kumasi, Ghana, but I got the opportunity to travel outside that region to do the field work to places like Accra, Nkawkaw and Bepong. I went on three collections and screened 16 total plant samples for antimicrobial activity. Of those, I prioritized the top three hits and I’m following up with those now. 

What about your experience surprised or intrigued you the most?

I was pretty surprised by the amount of work that actually goes into the getting the plant material and preparing the samples. Harvesting the plant material is a really physically demanding process. To get to our collection site, the day began with traveling four or five hours by trotro, a shared minibus, from Kumasi to Nkawkaw. Once there, you catch a taxi up to the village at the top of a mountain and meet with the local leader to offer a gift and get permission to go onto their land.  Then you set out on a 8 or so mile hike over mixed terrain in high heat and higher humidity until you come to the plant that you hope to retrieve plant tissues from. You give thanks to the spirit of the tree and begin to collect your samples—typically leaves, stem bark, or roots—and then you begin the long haul, carrying the plants material back with you for the return journey. It's seriously exhausting.

Once you’re back in the lab, the samples are processed: hand-cut into small pieces, dried in the sun and finely milled. It sounds simple, but the process takes days. Extracts from the plant material are prepared in a way that mimics the traditional uses. If the common preparation of the herbs is as a tincture made by infusing locally made spirits, then we might extract the samples in laboratory alcohols. Or if they make a tea, we’ll boil the samples in water. Then you let it sit for a few days before filtering and drying down the sample for testing. 

Don’t get me wrong. It sounds like I’m complaining, but what was the hardest part of the trip was actually the part that I was looking forward to doing the most. When you do the majority of your work in a lab,  it’s easy to lose perspective on the big picture and what motivated you to pursue science to begin with, but this was really an adventure like few others get to experience. It really felt like that—an adventure. And I’m really grateful to African Studies Center STEM seed program, to David Sherman and to the LSI for the support.

How does this work relate to what you hope to do in the future?

One of the things that I was really amazed at when I joined the Sherman group was the pivotal role that environmentally isolable small molecules have played in the development of health and human medicine. Natural products have really laid the foundation for the modern pharmaceutical paradigm. The Sherman lab and the Life Sciences Institute really take that potential for discovery to the next level. It’s easy to forget the biological origins of some of the drugs that we take for granted, but the story of Alexander Flemming discovering penicillin still blows me away. What is unique about this project is that we already know that these plants are efficacious because they’ve been in use as part of the traditional medical practices for thousands of years. 

Pharmacognosy, the study of the natural origins of drugs and bioactive materials, is something that I can see myself pursuing long-term.  Nature’s already done the hard work of making these chemicals, I think finding them and figuring out why they’re here is incredibly interesting and only beginning to really be looked at by the field.

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Top Image: Eisman and his team traveled by trotro to Nkawkaw, which sits at the base of Agogo-Mpraeso, then hired a driver to take them to Bepong, the village that will be the starting point of their foot journey through the brush.