Crafting A More Environmentally Benign Extraction and Analysis of Pharmaceutical Precursors from a Medicinal Plant: A Student-Led Innovation

A student-led research seminar was utilized to develop and validate an innovative 4-part undergraduate chemistry laboratory module that exposes students to a more environmentally benign method for the extraction and analysis of pharmaceutical-precursor alkaloids from the leaves of a medicinal plant, the Madagascar periwinkle. This plant is well known for its production of valuable pharmaceutical alkaloids but obtaining these compounds in therapeutic amounts has relied on traditional techniques that often ignore environmental impacts. Our student-directed design team has optimized an instructional protocol for extracting alkaloids from leaves by successfully, and for the first time, replacing the traditionally used dichloromethane extraction solvent with cyclopentyl methyl ether, a less environmentally harmful solvent. As a pedagogical exercise in the principles of green chemistry, students work in teams performing extractions with conventional vs. “green” solvents for comparison. We also introduce the student to the concept of the qualitative assay for alkaloid presence. Thin layer chromatography is performed with various solvents to optimize resolution of major alkaloid components, as well as to introduce fundamental principles of chromatography to the students. Finally, supercritical fluid chromatography is utilized as a previously unexplored, and less waste-producing analytical technique for confirmation of the presence of the valuable pharmaceutical precursors vindoline and catharanthine.