Herbal extracts may be prepared using one herb only, or a number of herbs could be used to obtain an extract with specific properties. However, when you require more accurate results, it is recommended to use a mixture of different herbal extracts in a definite ratio. The label on the packaging of commercial extracts would specify the ratio of herbs to solvent. Herbal extracts and different spices have been in use for centuries by native people from all over the world.