1. Definition and Basic Characteristics
We also call essential oils volatile oils. They are a general term for volatile oily components in plants.
These components have an aromatic odor. We can distill them with water vapor or extractants.
They are also immiscible with water. Volatile oils are complex mixtures.
The components extracted from different plants vary significantly. Currently, we use two main methods to extract volatile oils.
These methods are steam distillation and pressing. Most volatile oils are lighter than water.
Only a few are heavier than water. Examples include clove oil and cinnamon oil.
Their specific gravity generally ranges between 0.850 and 1.180. Therefore, most volatile oils are light oils.
Only a small number of them are heavy oils.
2. Solubility Characteristics
Volatile oils have poor solubility in water. However, they can dissolve completely in absolute ethanol.
They also dissolve fully in diethyl ether, chloroform, and fatty oils. They can dissolve in aqueous ethanol solutions of different concentrations.
The solubility varies with the ethanol concentration. The lower the ethanol concentration, the less volatile oil dissolves.
Volatile oils can slightly dissolve in water. This slight solubility imparts their unique aroma to the aqueous solution.
In medicine, we often utilize this property. We use it to prepare aromatic waters and injections.
Examples include mint water, Houttuynia cordata injection, and Bupleurum injection.
3. Effects and Chemical Composition
Most Chinese herbal medicines contain volatile oils. The extracted volatile oils also have similar effects.
These effects include diaphoresis, regulating qi, and relieving pain. They also have antibacterial activity and flavor correction functions.
Volatile oils from traditional Chinese medicines are active components. They consist of multiple constituents.
Besides aliphatic and aromatic hydrocarbons and oxides, they mostly contain terpenoids. These terpenoids exhibit good antibacterial effects.
