Extraction of Thyme Leaves and Analysis of Antibacterial Properties: An Adaptation for USF Analytical Chemistry Lab Course

We streamlined and adapted the thyme leaf extraction and analysis experiment developed by Purcell et al. at the University of California, Berkeley for the analytical chemistry lab course at the University of San Francisco. This experiment used the extraction and analysis of thyme leaves to familiarize students with an integrated laboratory approach, which is becoming increasingly popular in undergraduate chemistry education. The first goal of our research was to adapt the parameters of the experiment to the science writing heuristic (SWH), which moves away from verification-based activities and towards problem-based learning. A lab manual formatted for the SWH gives students a goal and basic experimental parameters, but has the students determine exactly how they are going to conduct the experiment. This means that the students will need to understand the experiment conceptually to complete the lab. The second major component of this project was adapting the methods of thin-layer chromatography, high-performance liquid chromatography, and Kirby-Bauer Disk Diffusion Assay. While our results were mostly consistent with those of Purcell, we calculated the concentration of thymol in thyme leaves to be 0.2% (w/w), while Purcell calculated a value of 2.11% (w/w). Additionally, we determined that carvacrol had more potent antibacterial properties than thymol, while Purcell found the opposite.