Galenicals
Introduction:
Extraction is the process of removing active constituents from plant or animal tissues using a liquid solvent known as the menstruum. The leftover insoluble material is called the marc. Galenicals, named after the Greek pharmacist Galen, refer to medicinal products derived via extraction of crude vegetable or animal drugs. Extracts contain all constituents soluble in the menstruum.
Types of Extracts:
- Dry extracts (e.g., belladonna extract)
- Soft extracts (e.g., glycerrhiza extract used in ointments or suppositories)
- Liquid extracts such as tinctures
Solvents Used in Extraction:
Water:
Solvent for proteins, gums, sugars, alkaloidal salts, organic acids, and salts. It is cheap, non-toxic, and non-inflammable but prone to microbial growth and may cause fermentation and hydrolysis. Requires heat to concentrate.
Alcohol:
Solvent for alkaloids, volatile oils, resins, tannins, and glycosides. Alcohol inhibits microbial growth if concentration is 20% or more, is neutral and non-toxic at used concentrations, requires less heat, and selectively dissolves active constituents. It is more costly than water and other organic solvents like ether or chloroform are used rarely.
Factors Affecting Extraction:
Nature of drug, solvent choice, temperature, pH, and particle size influence extraction efficiency.
Methods of Extraction:
- Infusion – soaking drug in hot water (sometimes in muslin cloth) for a short time
- Decoction – boiling the drug in water
- Digestion – maceration with gentle heat
- Maceration – soaking drug in menstruum for days with agitation
- Percolation – solvent passing through packed drug bed in a percolator
- Other modern methods: supercritical fluid extraction, microwave-assisted extraction, ultrasonication
Infusions:
Fresh infusion is dilute using boiling water, prepared for immediate use (e.g., orange infusion). Concentrated infusion is stronger using alcohol as solvent, stored longer, and prepared by repeated maceration.
Maceration:
For drugs with large soluble portions; the mixture stands for 7 days with periodic shaking, then filtered and marc pressed.
Percolation:
Continuous downward solvent displacement for efficient extraction used in tinctures and fluid extracts.
Soxhlet Extraction:
Continuous extraction using boiling solvent vapor and siphoning action, economical for large-scale extraction.
Preparation of Spirits and Tinctures:
Spirits are alcoholic or hydro-alcoholic solutions of volatile substances used internally or externally. Tinctures are made by maceration or percolation using alcohol-based solvents.
Understanding galenicals and their extraction is vital for pharmaceutical formulation and ensuring bioactive constituents are optimally obtained while removing unwanted components.
Detailed Notes:
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