Chemical and Physical Characterization of Verbenaceae Essential Oils Using Modern Analytical Methods and Chemometrics

Essential oils have been used for generations to treat various health issues, including mitigating insomnia, reducing stress, inflammation, and preserving foods, to mention a few. Essential oils have complex chemistry, which defines the essence of the host plant. Recently, increased commercial uses of essential oils have prompted attention at the governmental level to monitor the chemical, physical, or biological activity of essential oils. This study is an attempt to add new information for consumers to the understanding of the composition of essential oils. Modern analytical techniques including FTIR-ATR, GC-MS, LC-MS-MS, multivariate analysis statistics, and physio-chemical techniques (electrochemistry, DPPH, TRC, and antimicrobial assays) were used to characterize Verbenaceae essential oils. This is a family of plant products that have a history of treating respiratory and gastrointestinal related disorders. Using commercial essential oils mathematical models were built from the FTIR-ATR and GC-MS data to extract the chemical characteristics. These same models could be used to evaluate the quality of the essential oils. LC-MS-MS was to expand the chemical characterization. Electrochemistry explored the antioxidant activities of essential oils, which was compared to standard DPPH and TRC methods. The mathematical models provided useful variables to classify the essential oils from one another. With the input matrix ranging from 0-1, class predictions of the essential oils ranged from 0.84-1.18. LC-MS-MS offered new compounds that could not be accessed using GC-MS. SWV parameters, like total charge, correlated well with TRC results for antioxidant activity. Each of the oils exhibited adequate antibacterial activity, with subdued effects on the fungal species assessed.