Page 10 - Pharmd general phytochemistry I-Final2024_LEUCTERS

Methods of preparation of V.O:

1. Hydrodistillation.
2. Scarification and expression.
3. Extraction with solvents.
4. Enzymatic hydrolysis.
5. Supercritical methods.
The choose of the method depends on:
1. The condition of the plant material.
2. The location of the oil in the plant.
3. The amount of the oil.
4. The nature of the constituents of the oil.

1. HYDRODISTILLATION METHOD

This method is based on the fact that a mixture of water and immiscible
liquid (V.O.) boils at a temperature lower than water. ex. The boiling point
of turpentine oil is about 160°C, but on mixing with water and heating, the
mixture boils at about 95.6°C.
The principle of these methods is that, the boiling water or steam
penetrate the plant tissue and vaporizes all volatile substances.

 Before distillation the plant material must be subjected to size
reduction in order to expose a great number of oil glands. This process
termed "Comminution". Flowers, leaves and other thin and non-fibrous
parts of the plant can be distilled without comminution. Seeds and fruits
must be crushed. Roots, stalks and all woody materials should be cut into
short length.

There are three types of hydrodistillation:
a- Water distillation.
b- Water and steam distillation.
c- Direct steam distillation.

a- Water distillation:
The plant material is mixed directly with water in a still pot.

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