Publication in: Fall 2022 Issue

Supercritical Fluid Extraction of Native Appalachian Plants for Antibacterial
Reese Taylor
Faculty Mentor(s):
John W. Brock and Amanda Wolfe
Abstract / Summary:
Novel antibacterial compounds are in high demand due to antibacterial resistance creating a gap in viable treatment for various bacterial infections. These compounds can be developed synthetically, requiring several steps to design a lead compound, or they can be discovered through screening of compounds from natural sources. Synthetic development can be costly and time-consuming, thus the screening of natural compounds is favored. A wide diversity of unexplored natural sources exist, suggesting a method is needed to narrow the screening selection to plants most likely to contain antibacterial compounds. Plants used in traditional medicine, for conditions we know now as bacterial infections, can be explored for novel compounds. This research applies the screening of various traditional Appalachian medicinal plants using supercritical fluid extraction (SFE) to optimize the extraction of candidate compounds. Supercritical fluid extraction is highly efficient at extracting compounds from a matrix with exceptional precision. Extractions are varied by temperature, pressure, and polarity to extract a range of compounds from plant matter. The crude extractions are tested for inhibition of gram-positive Staphylococcus aureus and gram-negative Escherichia coli. For extractions showing antimicrobial activity, SFE parameters were further refined and re-evaluated to identify the exact parameters that extract the bioactive compound(s) to then be purified and characterized. Refined extractions with bioactive compounds were analyzed using LC-MS/MS to determine the specific compounds showing activity. Black Walnut (Juglans nigra), Sycamore Maple (Acer pseudoplatanus), White Oak (Quercus alba), and Joe-pye Weed (Eutrochium purpureum) were screened using these methods. Joe-pye Weed extracts showed significant inhibition of both Escherichia coli and Staphylococcus aureus, and was characterized by LC-MS/MS to identify the concentration of the known antibacterial compound, salicylic acid, in the inhibitory fractions.
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