Extraction and Antibacterial Properties of Thyme Leaf Extracts: Authentic Practice of Green Chemistry

Abstract

In this undergraduate analytical chemistry experiment, students quantitatively assess the antibacterial activity of essential oils found in thyme leaves (Thymus vulgaris) in an authentic, research-like environment. This multiweek experiment aims to instill green chemistry principles as intrinsic to chemical problem solving. Students progress through various techniques including extraction, chromatography (TLC and HPLC), culturing bacteria, and disk diffusion via a process of guided exploration that emphasizes green experimental design. Approximately 600 undergraduate students carried out the experiment and self-reported substantial learning gains.

Isolation of biologically active compounds from mangrove sediments

“…Similar to work presented here, extraction procedures involved the utilization of various organic solvents [28][29][30]. The range of chromatographic techniques varied from simple paper chromatography [31] and TLC [30,[32][33][34], with the latter noting, "the students recognize that TLC does not have the resolving power necessary to separate the extracted compounds and are guided towards a more powerful alternative, HPLC" [35]. HPLC is widely used in undergraduate teaching environments [35][36][37][38], so the utilization of HPLC in this paper is an obvious choice given the complexity of the extract.…”

“…The range of chromatographic techniques varied from simple paper chromatography [31] and TLC [30,[32][33][34], with the latter noting, "the students recognize that TLC does not have the resolving power necessary to separate the extracted compounds and are guided towards a more powerful alternative, HPLC" [35]. HPLC is widely used in undergraduate teaching environments [35][36][37][38], so the utilization of HPLC in this paper is an obvious choice given the complexity of the extract. For characterization of compounds, gas chromatography, sometimes coupled to a mass spectrometer (GC-MS), has been utilized [29,39,40] and in some cases, high-resolution mass spectrometry has also been used [39].…”

Design of a drug discovery course for non‐science majors

“…Supplemental readings are assigned from Napoleon’s Buttons: How 17 Molecules Changed History by Penny LeCouteur & Jay Burreson [16] and Laughing Gas, Viagra, and Lipitor: The Human Stories Behind the Drugs We Use by Jie Jack Li. [17] …”

“…In addition to offering a unifying theme for covering chemistry and biochemistry concepts in the classroom, the drug discovery theme is rife with possibilities for inquirybased laboratories. Previously described laboratory-based activities, including molecular modeling of pharmaceuticals [11,12], thin-layer chromatography-based analysis of analgesics [13,14], chemical synthesis of aspirin [15], screening of molecules for antimicrobial activity [16,17], and computer-aided drug design [18], fit seamlessly under the drug discovery umbrella. Further, drug discovery is a multidisciplinary topic that has connections to the history of scientific thought, the sociology of access to healthcare, the neuroscience of drug addiction, the public health impacts of antibiotic resistance, the economics of drug pricing, the laws behind patent protection, and the government oversight of pharmaceuticals, on top of the underpinning chemistry and biochemistry concepts.…”

Hydrodistillation and antimicrobial properties of lemongrass oil (Cymbopogon citratus, Stapf): An undergraduate laboratory exercise bridging chemistry and microbiology

“…Here, we bring together knowledge and skills from general chemistry and microbiology in a 4‐hr undergraduate laboratory exercise, where students carry out a hands‐on and research‐like experiment of essential oil extraction and antimicrobial activity testing. Extracting essential oils and studying their biological properties in undergraduate‐level laboratory exercise have been previously performed on thyme leaves ( Thymus vulgaris ) using Soxhlet extraction (Redfern, Kinninmonth, Burdass, & Verran, 2014), which takes 16 hr to complete, or organic solvent extraction (Purcell et al., 2016). The experiment presented here consists of extracting essential oil from lemongrass ( Cymbopogon citratus , Stapf) via hydrodistillation, and testing its antimicrobial properties against selected foodborne pathogens, namely, Escherichia coli , Bacillus subtilis , and Staphylococcus aureus .…”