Essential oils serve as a valuable, inexpensive natural supply of useful organic compounds that possess various biological activities, including antimicrobial properties, and most oils emit pleasant and familiar odors. They are an excellent source of analytes for introductory organic laboratory experiments. We report an experiment in which students rapidly isolate the major components of commercial essential oils (clove, oregano, red thyme, spearmint) by a small-scale modification of dry column vacuum chromatography (DCVC), a convenient reduced-pressure alternative to flash column chromatography, using an apparatus easily constructed from common laboratory glassware. They then experimentally establish the antibacterial activities of the oils and their two major components by testing for inhibition of bacterial growth on a nutrient agar plate.

The pharmacologically active lignans sesamin and sesamolin are minor components of sesame oil and ingredients in OTC dietary supplement capsules. We report an introductory undergraduate organic laboratory experiment combining natural product isolation and spectral analysis in which students isolate a mixture of sesamin and sesamolin by either (1) dry column vacuum chromatography (a convenient alternative to flash column chromatography) of commercial sesame oil using an apparatus constructed from common laboratory glassware or by (2) solid−liquid extraction of commercial sesame seed lignan dietary supplement capsules. Two recrystallizations from methanol remove most of the sesamolin to afford crystalline sesamin, which, due to its 2fold rotational symmetry, students can easily identify and characterize by NMR. During a second laboratory period, students perform a 5 min, test tube-scale reaction of sesamin with catalytic BF 3 :OEt 2 to promote its epimerization to episesamin, a diastereomer of sesamin lacking rotational symmetry, and the sesamin/episesamin ratio in the resulting product mixture is established by 1 H NMR integration. Students are asked to propose a mechanism for this epimerization based on their knowledge of the reactivity of benzyl ethers under acidic conditions.