Essential Oil Quality in Medicinal and Aromatic Plants: Linking Plant Biosynthesis, Matrix Selection and Extraction Strategy

Essential oils (EOs) are complex mixtures of volatile secondary metabolites produced by medicinal and aromatic plants (MAPs), mainly including terpenes, terpenoids and phenylpropanoid/benzenoid derivatives. Their composition depends on the plant species, chemotype, organ, developmental stage, environmental conditions and post-harvest processing, and directly affects EO yield, EO profile, biological properties, standardization and industrial value. This narrative and conceptual review connects plant biosynthesis, environmental regulation, matrix selection and extraction strategy as interdependent determinants of EO quality. Terpenoid constituents originate mainly from the mevalonate (MVA) and methylerythritol phosphate (MEP) pathways, whereas phenylpropanoid and benzenoid volatiles derive largely from the shikimate/phenylalanine pathway. Conventional extraction methods, such as hydrodistillation and steam distillation, remain widely used, while intensified and complementary approaches, including microwave-assisted methods, ultrasound pretreatment, supercritical CO2 extraction and solvent-free methods, are increasingly investigated to improve selectivity and reduce extraction time, solvent use, water demand and energy consumption. Rather than ranking extraction methods only by yield, this review emphasizes that EO quality should be interpreted through an integrated plant-to-extraction framework, in which botanical raw material, target chemical classes, matrix properties, compound stability and intended application jointly guide the selection of an extraction strategy. This integrated perspective may support more reproducible, application-oriented and sustainable EO production.