Essential oil from Aquilaria spp. (agarwood): a comprehensive review on the impact of extraction methods on yield, chemical composition, and biological activities

Agarwood essential oil (AEO), a highly prized medicinal substance, holds multifaceted applications across chemistry, traditional medicine, religion, and other domains. However, its limited yield poses a significant challenge to its widespread utilization. Conventional methods such as hydro-distillation (HD) and steam distillation (SD) do not ensure optimal extraction rates. Solvent extraction (SE) offers the potential for higher yields, albeit with the need for caution due to potential solvent residue hazards. Ultrasonic-assisted extraction (UAE) uses mechanical vibrations and cavitation to speed up extraction and increase yield, however it may damage bioactive chemicals over time. Microwave-assisted extraction (MAE), with its capacity to modify treatment conditions, presents an avenue to tailor functional components. Supercritical fluid extraction (SFE), while time-efficient, faces limitations due to its high cost. Enzyme pretreatment, despite its effectiveness, is not economically viable. Optimizing HD, UAE, and MAE concurrently can substantially reduce the duration and expense of AEO production, leading to higher yields. In addition, by adapting the composition to the unique characteristics of various extraction methods, AEO production can be enhanced, and a broader spectrum of functionalities can be explored. This article comprehensively reviews the impact of HD, SD, SE, UAE, MAE, SFE, and enzyme pretreatment on AEO yield, chemical composition, and biological functionality. It aims to furnish valuable insights into diverse extraction methods and component variations, thereby serving as a seminal reference for enhancing AEO yield and fostering extensive functional research.