Selectivity, solubility, cost and safety should be considered in selection of solvents. The selection of the solvent is crucial for solvent extraction. The properties of the extraction solvent, the particle size of the raw materials, the solvent-to-solid ration, the extraction temperature and the extraction duration will affect the extraction efficiency. Any factor enhancing the diffusivity and solubility in the above steps will facilitate the extraction. The extraction of natural products progresses through the following stages: (1) the solvent penetrates into the solid matrix (2) the solute dissolves in the solvents (3) the solute is diffused out of the solid matrix (4) the extracted solutes are collected. Solvent extraction is the most widely used method. Extraction methods include solvent extraction, distillation method, pressing and sublimation according to the extraction principle. This review intends to provide a comprehensive view of a variety of methods used in the extraction and isolation of natural products.Įxtraction is the first step to separate the desired natural products from the raw materials. There is an urgent need to develop effective and selective methods for the extraction and isolation of bioactive natural products. The lab-intensive and time-consuming extraction and isolation process has been the bottle neck of the application of natural products in drug development. The amounts of active ingredients in natural medicines are always fairly low. Natural products offer more drug-like features to molecules from combinatorial chemistry in terms of functional groups, chirality, and structural complexity. From the 1940s to the end of 2014, nearly half of the FDA approved chemical drugs for the treatment of human diseases were derived from or inspired by natural products. Natural products have provided the primary sources for new drug development. Chemicals known to have medicinal benefits are considered to be “active ingredients” or “active principles” of natural medicines. In the USA, approximately 49% of the population has tried natural medicines for the prevention and treatment of diseases. Today, natural medicines not only provide the primary health-care needs for the majority of the population in developing countries but have attracted more and more attention in developed countries due to soaring health-care costs and universal financial austerity. Natural medicines, such as traditional Chinese medicine (TCM) and Ayurveda, were formed and developed in the daily life of ancient people and in the process of their fight against diseases over thousands of years, and they have produced a positive impact on the progress of human civilization.
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