Once botanical identity is established, the next step is preliminary phytochemical screening. This screening involves extraction, purification and characterisation of the active constituents of pharmaceutical importance. The herbal drug or herbal drug preparation in its entirety is regarded as the active substance. These constituents are either of known therapeutic activity or are chemically defined substances or groups of substances generally accepted to contribute substantially to the therapeutic activity of an herbal drug. Qualitative chemical examination is done to detect and isolate the active constituent(s). High performance liquid chromatography (HPLC) is the main analytical technique for quantitative measurements of active compounds. In cases when active ingredients are not known or are too complex, the quality of plant extracts can be assessed by a “fingerprint” chromatogram.
Standardisation means adjusting the herbal drug preparation to a defined content of a constituent or a group of substances with known therapeutic activity by adding excipients or by mixing herbal drugs or herbal drug preparations. Botanical extracts made directly from crude plant material show substantial variation in composition, quality and therapeutic effects. Standardised extracts are high quality extracts containing consistent levels of specified compounds, and they are subjected to rigorous quality controls during all phases of the growing, harvesting and manufacturing processes.
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