Chapter 11 - Modern solvent-free microwave extraction with essential oil optimization and structure-activity relationships

Abstract

Essential oils (Eos) are naturally occurring compounds derived from higher plants and are extensively used in various industries, including agriculture, cosmetics, foods, pharmaceuticals, perfumery, and textiles. The successful utilization of these oils necessitates reliable extraction, isolation, and analytical methods to maintain product quality. However, most EOs obtained for commercial purposes are still extracted using traditional processes. Innovative advances and groundbreaking technology have motivated researchers to apply green chemistry strategies to perform extraction without the use of toxic solvents and to explore alternative, ecologically friendly, and energy-efficient manufacturing techniques. Modern extraction technology utilizing a solvent-free microwave method represents a platform that takes advantage of the strengths of solvent-free techniques. This modern approach can provide increased predictability and selectivity, rapid isolation processes, and decreased energy consumption when combined with response surface methodology (RSM). The resulting oil constituents possess broad-spectrum bioactivities, and analyzing their structure-activity relationship is vital for identifying targets and optimizing leads in the development of bioactive agents. Thus, this chapter compiles and synthesizes information on the application of solvent-free microwave extraction in EO research, the implementation of RSM in the optimization process, and SAR studies of key components. Global research trends using systematic bibliometric analysis are also explored. This review will help readers understand modern solvent-free EO extraction, advances in the current science, research gaps, and trends in EO research and applications for sustainable development.