Biosynthesis of Essential Oil in Aromatic Plant Species: A review

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ABSTRACT

Essential oils (EOs) are complex mixtures of volatile secondary metabolites synthesized in aromatic plants, valued for their therapeutic, aromatic, and industrial applications. This review provides a comprehensive analysis of the biosynthetic pathways involved in essential oil production, emphasizing the enzymatic and genetic regulation underlying terpenoid formation. Essential oils are primarily derived from two distinct metabolic pathways: the cytosolic mevalonate (MVA) pathway and the plastidic methylerythritol phosphate (MEP) pathway. Both pathways produce the universal precursors, isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP), which serve as the foundation for terpenoid biosynthesis. Terpene synthases (TPS) catalyze the conversion of these precursors into diverse terpenoids, including monoterpenes (C10), sesquiterpenes (C15), diterpenes (C20), and higher-order terpenes, each contributing to the characteristic fragrance and biological activity of essential oils. The commercial significance of essential oils is immense, with applications spanning pharmaceuticals, cosmetics, food flavoring, and aromatherapy. The global market for essential oils is projected to grow from USD 10.3 billion in 2021 to USD 18.25 billion by 2028, driven by increasing demand for natural and organic products. However, optimizing EO production requires deeper insights into metabolic engineering, environmental influences on biosynthesis, and genetic manipulation of key enzymatic steps. This review consolidates current knowledge on terpenoid biosynthesis, discusses the roles of critical enzymes and genes, and highlights future research directions to enhance EO yield and diversification. Understanding these mechanisms will facilitate the development of sustainable strategies for industrial-scale essential oil production.

Significance of the Study:
This study provides a comprehensive analysis of the DXP pathway enzymes—MCT, CMK, and MDS—critical for plastidial isoprenoid biosynthesis in plants. By elucidating their structural, functional, and regulatory mechanisms, the research advances our understanding of terpenoid production, which underpins essential ecological and economic processes, including plant defense, pollination, and pharmaceutical compound synthesis. The findings offer potential applications in metabolic engineering for enhanced essential oil yields and the development of targeted herbicides or antimicrobials, leveraging the pathway’s absence in mammals.

Summary of the Study:
The study systematically examines three key enzymes (MCT, CMK, MDS) in the DXP pathway, detailing their roles in converting metabolic intermediates to terpenoid precursors. Through structural and kinetic analyses, it highlights their plastid localization, catalytic mechanisms, and regulatory features. The research bridges gaps in plant isoprenoid biosynthesis, offering insights for biotechnological manipulation of terpenoid production. These discoveries pave the way for sustainable applications in agriculture, medicine, and industry by optimizing natural product synthesis.