Page 112 - phytochemistry I - PharmD Clinical

solution decreases until it stabilizes at +52.7°. On the other hand, a
recently dissolved aqueous solution of β-glucose has a specific rotation
of +18.7°, but in subsequent measurements, this value increases
stabilizing at +52.7°considering that α-glucose has a higher specific
rotation than β-glucose. Thus α-glycoside solution shows gradual
decrease in the optical rotation till equilibrium. On the contrary, β-
glycoside solution shows gradual increase in the optical rotation till
equilibrium.

Extraction of glycosides:

Isolation of glycosides from plants is often difficult and sensitive to
temperature and humidity. This is due to the presence of plant enzymes
that may cause their own hydrolysis.

General procedure for extraction:

First drying the fresh plant material in a special oven. Then the dried plant
material is boiled with organic solvents for 20 minutes. After that, lead
acetate must be added to the plant containing tannins or resins to
precipitate them.

Steps of the extraction procedure:

1. A method must be adopted for Deactivation of enzymes, it can
be one of the following:

• Drying for 15-30 min at 100°C followed by slow drying at a low
temperature.

• Dipping the fresh material into boiling water or boiling alcohol for 10-
20 min.

• Boiling the fresh plant material with acetone.
• Carrying out the extraction at very low temp.
• Freeze-drying of the plant material before extraction (lyophilization).

2. Maintenance of neutral conditions:
Neutral pH should be assured before and during extraction because
acidity may result in hydrolysis.

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