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MindMap Gallery Natural Medicinal Chemistry General Introduction-Isolation and Purification

Natural Medicinal Chemistry General Introduction-Isolation and Purification

This is a mind map about natural medicinal chemistry - separation and purification, including solubility, Distribution ratio, adsorption, molecular size, degree of dissociation, etc.

Edited at 2024-01-16 20:20:47

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Natural Medicinal Chemistry General Introduction-Isolation and Purification

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Outline

Separation and refining

Isolation and refining of natural medicinal ingredients

Homogeneous and heterogeneous

Heterogeneous mixture: There are interfaces between materials in the system and their properties are completely different; gas-solid separation, liquid-solid separation and liquid-liquid separation, such as: dust removal, filtration, extraction, distillation, etc.

Homogeneous mixture: There is no interface between materials, which refers to miscible extracts with different components.

The principle of separation and refining: utilizing the differences in properties of coexisting components

Such as solubility, distribution ratio, adsorption, molecular size, degree of dissociation

solubility

Adjust temperature: crystallization, recrystallization

Change solvent polarity

Method: Add another solvent with a large difference in polarity → the polarity of the mixed solvent changes → some substances precipitate out

type: Water/alcohol method: remove water-soluble impurities in the water extract (the target component is in the mother liquor) Alcohol/water method: remove fat-soluble impurities in the alcohol extract (the target component is in the mother liquor) Alcohol/ether method (alcohol/acetone method): purification of saponin (the target product is precipitating)

Adjust pH

Acid extraction and alkali precipitation method: alkaloids; alkali extraction and acid precipitation method: flavonoids, anthraquinones; adjusting pH to isoelectric point: precipitating proteins

Add precipitation reagent

Acidic components: Precipitation reagents: Pb2, Ba2, Ca2 Operation: Suspension in precipitated water, pass through H2S, mother liquor (√)

Basic compounds: precipitation reagents: picric acid/picric acid, phosphomolybdic acid/phosphotungstic acid/radium acid Operation: precipitation, strong acid, Et2O extraction, H2O layer (√)

Distribution ratio

Separate substances based on different distribution coefficients

Distribution coefficient: K=CU/CL (CU is the concentration of solute in the upper phase solvent) Separation factor: β=KA/KB (KA > KB) • β > 100: 1 extraction, basic separation • 10 ≤ β ≤ 100: Extraction 10~12 times • β ≤ 2: extraction more than 100 times • β ≈ 1: cannot be separated

Method classification

Simple liquid-liquid extraction

Conditions: β>50; Method: organic solvent/water; organic solvent/acid, alkaline water (pH → substance existence state → solubility → K); pH gradient extraction (gradient adjustment of pH, changing the existence state of one component at a time , separated in turn)

Partition coefficient and pH: Acidic substances: Acidic substances are completely dissociated at pH=pKa 2, and acidic substances are completely dissociated at pH=pKa-2. Alkaline substances: The larger the pKa of the conjugate acid, the more alkaline it is. When pH<3, most acidic substances are in free state and alkaline substances are in dissociated state.

Countercurrent Dissolution (CCD), Droplet Countercurrent Chromatography (DCCC)

Applicable to: β<50; Principle: multiple, continuous liquid-liquid extraction

High speed countercurrent chromatography (HSCCC)

Principle: The centrifugal force field generated by planetary rotation keeps the stationary phase in the serpentine tube, and the mobile phase passes through the stationary phase in one direction and at a low speed, achieving the purpose of continuous countercurrent extraction and separation of substances.

Paper Chromatography (PC)

Liquid-liquid distribution column chromatography

Normal phase chromatography and reversed phase chromatography

Octadecyl silica column (ODS/RO-18) can only use methanol/ethanol and water as eluent

Pressurized liquid column chromatography

Flash chromatography: ~ 2bar Low pressure liquid chromatography LPLC: <5 bar Medium pressure liquid chromatography MPLC: 5 ~ 20 bar High pressure liquid chromatography HPLC: >20 bar

Turbulence Chromatography (TFC)

Principle: Small molecular substances: small mass transfer impedance and small column efficiency loss; large molecular substances: have no time to enter the inside of the packing and are washed out of the column

Conditions: large particle size packing, mobile phase under high speed conditions (7.5 cm/s), generating vortex state

Purpose: It can remove macromolecules in the solution and realize direct analysis of biological samples.

Paradigm equation: H=A B/u Cu, u—mobile phase linear velocity A—eddy current diffusion coefficient B—molecular diffusion coefficient (longitudinal diffusion term) C—Mass transfer resistance coefficient (including liquid phase and solid phase mass transfer resistance coefficient)

Ion pair chromatography, ion suppression chromatography and ion exchange chromatography

Ion Pair Chromatography (IPC)

Operation: Add acid, alkali, or salt to the mobile phase; Purpose: To inhibit the dissociation of acids and bases to be tested, and add salt to reduce the interaction between the test objects and residual silanol groups; Scope of application: Add acid and alkali to separate acids and bases Neutral compounds; adding salt improves retention behavior of neutral substances

Ion Suppression Chromatography (ISC)

Operation: Add an ion pair reagent (B) with an opposite charge to the ion to be measured (A) into the mobile phase (usually the organic phase); Purpose: To make the ion to be measured A and the counter ion B form an ion pair AB; Scope of application: Separation Strongly polar organic acids and organic bases

adsorption

Law of physical adsorption: like attracts like

physical adsorption

Intermolecular force, non-selective, reversible; silica gel, alumina, activated carbon

chemical adsorption

Chemical bonds, strong selectivity, often irreversible; silica gel, alkaloids; alkaline alumina, flavonoids, anthraquinones, etc.

Semi-chemical adsorption

Hydrogen bonding, weak selectivity, mostly reversible; polyamide

Type of adsorption

polar adsorbent

Strong adsorption of polar samples Mobile phase polarity ↑, adsorption force ↓, elution force ⬆

non-polar adsorbent

Strong adsorption of non-polar components Mobile phase polarity ↑, adsorption force ↑, elution force ⬇

If the sample is highly polar and is to be separated on a polar adsorbent column, an adsorbent with weaker adsorption (i.e. lower activity) should be used and a more polar solvent should be used for elution. If the polarity of the component is weak, an adsorbent with strong adsorption (i.e. higher activity) should be used, and a less polar solvent should be used for elution.

Polarity and strength judgment

Solvent

Determine based on the type, number, position, and length of the carbon chain of the functional group; the longer the carbon chain, the lower the polarity.

R-COOH﹥ Ar-OH﹥ R-OH﹥ R-NH-﹥ R-CO-NH-﹥ R-CHO﹥ R-COR﹥ RCOO-R﹥ R-O-R﹥ R-X﹥ R-H

general matter

The greater the dielectric constant ε, the greater the polarity.

Cyclohexane＜Benzene＜Anhydrous ether＜Chloroform＜ethyl acetate＜Ethanol＜Methanol＜Water

Simple adsorption method is used to concentrate and purify substances

Activated carbon adsorption

Decolorization and deodorization during crystallization and recrystallization Concentrate trace substances from dilute aqueous solutions, such as: Concentration and purification of hematine

Magnesium oxide adsorption

Decolorization of saponin extracts, such as refining of ginsenosides

Silica gel, alumina column chromatography

Adsorbent dosage: 30-60 times the sample volume

Operation: column packing, sample loading, elution, tailing, selection of elution system: Rf value 0.2-0.3

Polyamide column chromatography

Factors affecting adsorption capacity

• More -OH • C=O more • Few H bonds in the molecule • High degree of aromatization • Small MW

Usage: Preparation and separation of phenolics such as quinones and flavonoids; detanning treatment; separation of other polar and non-polar compounds

Solvent elution ability

The adsorption force of a compound in a solvent increases as the polarity of the solvent increases

The strongest in water: water is often used to fill the column, and the sample is dissolved in water and loaded, followed by water-containing alcohols, and the weakest among alcohols: often eluted with a gradient of water-containing alcohols with increasing concentrations. EtOH-H2O is most commonly used

Elution power: water < methanol < ethanol < sodium hydroxide aqueous solution < formamide < dimethylformamide < urea water solution

macroporous adsorption resin

Separation principle: adsorption principle (intermolecular force, hydrogen bonding); molecular sieve

molecular size

Dialysis: often used to remove salts and small molecules from macromolecules

Membrane filtration method: including microfiltration, ultrafiltration, nanofiltration, reverse osmosis, etc.

Ultracentrifugation

Size exclusion chromatography (SEC)

Principle: Molecular sieve with a three-dimensional network structure of gel; separation in order from large to small molecular weight

Types, properties and applications of gels

Hydroxypropyl dextran gel: separation mechanism (molecular sieve), application range (separation of water-soluble components)

Polysaccharide gel: separation mechanism (combination of molecular sieves and reversed-phase chromatography), application range (can separate water-soluble and fat-soluble components)

Molecular sieve filtration

degree of dissociation

The structure of ion exchange resin: mother core, ion exchange group

Type: Cation exchange resin: Strongly acidic (-SO3-H), weakly acidic (-COO-H) Anion exchange resin: Strongly basic (-N (CH3)3Cl-), weakly basic (-NH2, -NH-, -N=)

Application: Separation of compounds with different charged ions (acid, alkali, amphoteric); Separation of ions with different degrees of dissociation (different acidity and alkalinity) (PPT example: Alkalinity is getting stronger and stronger)

Process: Ion exchange resin is the stationary phase - water or aqueous solvent is packed into the column - the aqueous mobile phase passes through the resin - exchangeable ions are exchanged with the exchange groups on the resin and adsorbed to the resin - neutral and non-exchangeable ion components flow out - the adsorbed The components on the column are eluted