The Extraction and Purification of Natural Products In addition our chemical synthesis and biopharmaceutical manufacturing services, PharmaSynth has capabilities in natural products extraction, purification and characterisation. A "natural product" is a chemical compound or substance produced by a living organism that is found in nature. Natural products may be produced by the chemical extraction of plant or animal tissues followed by isolation and purification of the final product. In other cases, a molecule might be harvested from an organism and then this precursor molecule further modified outside the organism to produce the desired product â€” a process called "semisynthesis". On the other hand, in organic chemistry, a "total synthesis" is, in principle, the complete chemical synthesis of complex organic molecules from simpler pieces without processing of the molecules within a living organism or "biological factory". However, not all natural products can be fully synthesized. Also many natural products have very complex structures that are too difficult and/or expensive to synthesize on an industrial scale through total synthesis. Natural products that can be isolated or produced from plants are called "phytochemicals." The natural products industry is particularly interested in secondary metabolic compounds found in plants. "Secondary metabolites" are organic compounds that are not directly involved in the normal development, growth, or reproduction of an organism. In agriculture, many "secondary metabolites" are known to provide protection against insect attacks and plant diseases. Secondary metabolites produced by plants can also be used in medicines, as flavorings, or in consumer products. If the lead compound (or active principle) of interest is present in a mixture of other compounds from a natural source, it has to be extracted and purified. Secondary metabolites can be extracted from a variety of natural sources, including plants, microbes, marine animals, insects, and amphibians. With regard to laboratory-scale processes of initial and bulk extraction from plant and microbial sources, the steps required for the preparation of the material prior to extraction, including aspects concerning plant selection, collection, identification, drying, and grinding. The various extraction methods available include maceration, ultrasound-assisted solvent extraction, percolation, pressurized solvent extraction, Soxhlet extraction, extraction under reflux, steam distillation, and acid/based extraction. The extraction process in general must be streamlined to reduce solvent consumption since solvent removal can present a major process bottleneck. Also an important concept is to choose an extraction method that supports the first step used in fractionation. For initial fractionation of any crude extract, it is advisable not to generate too many fractions, because it may spread the target compound over so many fractions that those containing the compound in low concentrations might evade detection. It is more sensible to collect only a few large relatively crude fraction and then quickly home in on those containing the target compound. Often preparation chromatography is utilized - a physical method of separation in which the components to be separated are distributed between two phases, one of which is stationary (stationary phase) while the other (the
mobile phase) moves in a definite direction. One example would be preparative liquid chromtaography (LC). The active fractions from LC are then undergo a more finer fractionation such as by semipreparative or high-performance liquid chromatography (HPLC), often guided by an on-line detection method such as ultraviolet light (UV) or mass spectrometry (MS). The combination of liquid chromatography and mass spectrometry is denoted by the acronym "LC-MS." Once an compound of interest is detected in a fraction, an important technique for determining the chemical structures of the compound is nuclear magnetic resonance spectroscopy (NMR) which yields information about individual hydrogen and carbon atoms in the structure, allowing detailed reconstruction of the moleculeâ€™s architecture. Finally, it is important to determine if a compound purified utilizing the above techniques has biological activity. For that purpose, bioassays are developed and put into play based on the use of a biological system to detect properties important for the activity of the molecule (e.g., antibacterial, antifungal, anticancer, anti-HIV, anti-diabetic, etc.). Bioassays could involve the use of in vivo systems (e.g., whole animal experiments), ex vivo systems (isolated tissues and organs), or in vitro systems (e.g., cultured cells).
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