Student Research Enhances the Antibacterial Effectiveness of a Common Sugar Alternative

Ariel Richards ’23, a chemistry major, was only able to experience in-person labs for a few months before the pandemic began. So, she returned to campus in the spring of 2021 for a chemistry Mentored Independent Project and stayed that summer for a chemistry Mentored Advanced Project under the supervision of Erick Leggans, professor of chemistry. “I really wanted to get my hands —,” she pauses and then continues, “I don’t want to say dirty because I don’t want my hands to be dirty with chemicals.”

Richards got her hands metaphorically dirty by carrying out pharmacognosy research, research that helps develop drugs from compounds produced by organisms. Through this research, she participated in both the College’s Mentored Advanced Project program and the American Society of Pharmacognosy’s Summer Research Fellowship. The fellowship supports seven students in lab research and includes weekly trainings and professional development workshops.

In part through this fellowship, the American Society of Pharmacognosy is working to make graduate school and careers in pharmacognosy more equitable. Richard’s cohort was all women of color and many of the workshop leaders were also people of color, which created a refreshing atmosphere for Richards. “I just felt comfortable,” she says.

From Sugar Alternative to Antibacterial

Richards’s research stems from the plant Stevia rebaudiana, which is composed of a core molecule, steviol, and sugars that are a common alternative to conventional sugar. Steviol is a structural analog of isosteviol — there are only slight differences between the two compounds.

There is some research to suggests steviol has antibacterial properties. Richards wanted to find out whether modifying steviol and isosteviol could enhance their antibacterial effectiveness, a question that is especially important as more bacteria develop resistance to existing antibacterials.

Persistence and Discovery

Richards began by removing the sugars from steviol and isosteviol. That ended up taking six of the ten weeks she had to finish her project. Frustrating as that was, Leggans and the fellowship mentors encouraged and supported Richards in troubleshooting and persisting when her experiments didn’t go as planned.

One day, Richards changed her starting material to a different brand of Stevia. When she did, a sickly sweet smell wafted from her product. That smell is associated with isosteviol — she had successfully removed the sugars!

She then modified isosteviol by adding common essential oils known for their antibacterial properties and placed discs of the modified isosteviols onto plates covered with bacteria. For controls, she placed discs made of the same liquid she used to dissolve her compounds, discs made of unmodified isosteviol, and discs made of a known antibacterial on plates. The compounds diffuse from the discs onto the bacteria-covered plates, and the bacteria growth in response indicates the antibacterial effectiveness — less growth indicates higher effectiveness and vice versa.

As expected, the plates with discs made of the same liquid she used to dissolve her compounds and those with discs made of unmodified isosteviol had significant bacteria growth and the plates with discs made of a known antibacterial had clear rings around the discs where the antibacterial prevented bacteria growth. But as Richards had hoped, some plates with discs made of the modified isosteviols also had clear rings — some modified isosteviols did enhance antibacterial effectiveness.

Gaining Knowledge and then Creating It

Richards presented her research at a poster session with other chemistry MAP students and at a virtual seminar for American Society of Pharmacognosy members. It was during those presentations that she realized, “Wow! I did so much.”

“A few months before, I was learning organic chemistry,” she reflects. “There’s a stark difference between pre-research Ariel and post-research Ariel.”

Stepping through Doors, Opening More

Richards is still deciding what she wants to do after graduation, but she says, “I definitely would do research. … I found it fun.” Her experience enabled her to develop many pharmacognosy and chemistry research skills, which would be a solid foundation for a research career if she chooses to pursue one.

However, her experience also enabled her to develop skills that will be useful in any profession. Overall, she says her experience gave her “more options, more space to navigate through.”