In general, the agarwood extraction method depends on the purpose of the extract. The agarwood essential oils are obtained through hydrodistillation, or steam distillation. The chemical constituents of agarwood usually obtained from the solvent extraction, such as acetone, methanol, ethanol and water or supercritical fluid extraction. Various extraction process such as maceration, soxhlet, supercritical fluid, ultrasonic-assisted, microwave-assisted, and high-pressure processing extractions are used to get the desired extract/compounds.
Each solvent and/or extraction process produces different extracts in terms of quantity and quality of the constituents. Although water is a cheap solvent and relatively safe, however, aqueous extracts resulted the impurities that makes difficult to isolate the desired compound. Therefore, after the aqueous extraction process, the crude extract was fractionated with hydroalcohol into the desired compounds. This technique is widely applied, especially in the whole process of extraction of the agarwood.
Methanol also suitable as an extraction solvent since aqueous methanol was more effective in extracting total sesquiterpenes, 2-(2-phenylethyl)-4H-chromen-4-one derivatives (PECs), and aromatic compounds as compared with water. Alternatively, ethanol is also a suitable solvent for agarwood extraction. It is a non-toxic for human consumption, and widely used for natural products extraction. Most secondary metabolities are dissolved in ethanol except protein, phlegm, pectin, starch and polysaccharide.