Most of medicinal herbs are not—in their natural state—fit for administration. Preparations suitable for administration are made according to pharmacopoeial directions. Herbal infusions are prepared by treating the herb to be extracted with water or alcohol. An herbal drug reduced to powder form is known as pulverata. Tinctures are solutions of the active principles of a drug in alcohol. A coarsely bruised drug boiled in water for a definite period is known as decoction.
Herbal extracts are considered to be scientific pharmacopoeial preparations. Liquid extracts, concentrated soft extracts and dry extracts are all used for industrial applications. Herbal extracts are prepared by extracting an herb of a specific particle size with suitable solvent. Depending on the solvent used, extracts are known as aqueous, alcoholic or etheral extracts. The extracts also contain marker compounds that are important for the quality of the finished product. Markers are chemically defined constituents of a herbal drug, which are of interest for quality control purposes (independent of whether they have any therapeutic activity or not). Extract of Hypericum perforatum (i.e., St. John’s Wort) is a good example of how extracts are standardised to marker compounds (0. 3% hypericin) and active constituent (2. 8% hyperforin).In the case of medicinal herbs, before a consignment is evaluated, a sample is drawn for analysis and considerable care is exercised to ensure that this sample is truly representative. Macroscopic and sensory characters are usually sufficient to enable the drugs to be identified. Thin Layer Chromatography (TLC) is a good tool for determining the botanical identity of the herb. Moisture content, extractive value and ash value are also used as standards for preliminary examination. Swelling index is standard specified, applicable to mucilage-containing drugs. Inadequate quality control of herbal drugs is a significant concern for consumers and manufacturers.
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