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Syllabus of Unit 5 :-

Basics of Phytochemistry
Modern methods of extraction, application of latest techniques like Spectroscopy, chromatography and electrophoresis in the isolation, purification and identification of crude drugs.

Modern Method of Extraction :-

Extraction is that the beginning to separate the specified natural products from the raw materials. Extraction methods include solvent extraction, distillation method, pressing and sublimation in keeping with the extraction principle. Solvent extraction is that the most generally used method. The extraction of natural products progresses through the subsequent stages: the solvent penetrates into the solid matrix; the solute dissolves within the solvents; the solute is diffused out of the solid matrix; the extracted solutes are collected. Any factor enhancing the diffusivity and solubility within the above steps will facilitate the extraction. The properties of the extraction solvent, the particle size of the raw materials, the solvent-to-solid ration, the extraction temperature and also the extraction duration will affect the extraction efficiency.

The selection of the solvent is crucial for solvent extraction. Selectivity, solubility, cost and safety should be considered in selection of solvents. supported the law of similarity and intermiscibility (like dissolves like), solvents with a polarity value regarding the polarity of the solute are likely to perform better and the other way around. Alcohols (EtOH and MeOH) are universal solvents in solvent extraction for phytochemical investigation.

Generally, the finer the particle size is, the higher result the extraction achieves. The extraction efficiency are enhanced by the tiny particle size thanks to the improved penetration of solvents and diffusion of solutes. Too fine particle size, however, will cost the excessive absorption of solute in solid and difficulty in subsequent filtration.

High temperatures increase the solubility and diffusion. Temperatures that too high, however, may cause solvents to be lost, resulting in extracts of undesirable impurities and also the decomposition of thermolabile components.

The extraction efficiency increases with the rise in extraction duration in a very certain time range. Increasing time won't affect the extraction after the equilibrium of the solute is reached inside and outdoors the solid material.

The greater the solvent-to-solid ratio is, the upper the extraction yield is; however, a solvent-to-solid ratio that's too high will cause excessive extraction solvent and requires a protracted time for concentration.

The conventional extraction methods, including maceration, percolation and reflux extraction, usually use organic solvents and need an outsized volume of solvents and long extraction time. Some modern or greener extraction methods like super critical fluid extraction (SFC), pressurized liquid extraction (PLE) and microwave assisted extraction (MAE), have also been applied in natural products extraction, and that they offer some advantages like lower organic solvent consumption, shorter extraction time and better selectivity. Some extraction methods, however, like sublimation, expeller pressing and enfleurage are rarely employed in current phytochemical investigation and can not discussed during this review