User:Prince shoaib/Methods of extracting drug from plants

Extraction
Extraction refers to processes for the isolation of the active ingredients from drug material. This may be by physical means or by dissolving in a suitable menstruum (liquid solvent eg. water or alcohol).

Expression
Expression is the physical act of applying pressure to squeeze out oils or juices from plants. This was normally achieved with a tincture press.

Infusions
Infusions are prepared by simply soaking a drug in water for a specified time. This might be hot or cold, depending on whether decomposition of ingredients could occur at higher temperatures. Infusions would normally be prepared for immediate use, as there is no preservative present. In some cases concentrated infusions might be prepared by boiling to reduce the water then adding a preservative such as alcohol.

Decoction
Decoctions are prepared in a similar way to infusions but with the ingredients and water boiled for a specified period of time or until a certain volume is achieved.

Maceration
Maceration differed from the above two processes in that the drug was left in contact with the menstruum, usually alcohol but sometimes water, for a longer period of time. The usual procedure would be to add the liquid to the drug in a closed vessel for seven days, shaking occasionally, straining, pressing the marc (the remaining drug/liquid mixture), mixing the two solutions and clarifying by filtering or by standing.

Percolation
Percolation differs slightly from maceration. The powdered drug is dampened with the menstruum, left for four hours then packed into a percolator. Sufficient menstruum is added to cover the drug and left for twenty-four hours. The liquid is then allowed to very slowly drain from the bottom of the percolator (about twenty drops per minute). More menstruum is added and the process continued until the volume in the collecting flask reaches about three-quarters of the required volume. The marc is pressed, this liquid added to the flask, more menstruum added to make the specified volume then the whole liquid is clarified.