Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev
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Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev

Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev

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30.10.2014 Views

13 COUNTER-CURRENT CHROMATOGRAPHY 13.2.4 Applications of Droplet Counter-current Chromatography This simple DCCC instrument has been used to perform effi cient preparative separations such as: • Separation of non-polar compounds. • Isolation of virginiamycin-M1 and parthenolide. • Isolation of vitamin B12. • Pharmacognostical studies of Tabernaemontana species: ion-pair DCCC of indole alkaloids from suspension cultures. • Chiral resolution of a carboxylic acid. • Separation of natural polar substances by reverse phase HPLC, centrifugal thin layer chromatography and DCCC. • Effi cient isolation of ecdysteroids from the silkworm, Bombyx mori. • Analytical DCCC isolation of 20-hydroxyecdysone from Vitex thyrsifl ora (Verbenaceae). • Increasing the speed of DCCC separations. • Complete resolution of isoleucine. • DCCC of anthocyanins. • Effi cient isolation of phytoecdysones from Ajuga plants by high-performance liquid chromatography and DCCC. • DCCC with non-aqueous solvent systems. • Use of DCCC in log P determinations. • Purifi cation of Stevia rebaudiana sweet constituents (potential sweetening agent of plant origin). • Water-free solvent system for DCCC and its suitability for the separation of non-polar substances. • Isolation of phorbol, 4α-phorbol and croton oil. • Purifi cation of antibiotics such as gramicidins, tyrocidines and tetracyclines. 13.2.5 Limitations of DCCC • Extremely low fl ow rates (sometimes solute retention is measured in days). • Only biphasic solvents systems that form stable droplets can be used. • Poor mixing of phases, which results in relatively low effi - ciency. 13.2.6 Modern Counter-current Chromatography Modern CCC has split into two basic directions. The fi rst, which is called High-speed Counter-current Chromatography (HSCCC), uses an apparatus with a variable gravity fi eld produced by a double axis gyratory motion (Figure 4). The second, termed Centrifugal Partition Chromatography 214

EXTRACTION TECHNOLOGIES FOR MEDICINAL AND AROMATIC PLANTS (CPC), employs a constant gravity fi eld produced by a single axis rotation, together with rotatory seals for supply of solvent. Separation takes place in cartridges or disks. CPC with cartridges or disks is a hydrostatic equilibrium system. If the coil is fi lled with the stationary phase of a biphasic solvent system and then the other phase is pumped through the coil at a suitable speed, a point is reached at which no further displacement of the stationary phase occurs and the apparatus contains approximately 50% of each of the two phases. Steady pumping-in of mobile phase results in elution of mobile phase alone. This basic system uses only 50% of the effi cient column space for actual mixing of the two phases. A more effective way of using the column space is to rotate the coil around its central axis while eluting the mobile phase. A hydrodynamic equilibrium is rapidly established between the two phases and almost 100% of the column space can be used for their mixing. CCC with rotating coil instruments is an example of this latter mechanism. • The planetary motion is produced by engaging a planetary gear mounted on the column holder axis to an identical stationary sun gear rigidly fi xed to the centrifuge framework. • This 1:1 gear coupling produces a particular type of planetary motion of the column holder, i.e. the holder rotates about its own axis while revolving around the centrifuge axis at the same angular velocity (synchronous) in the same direction. • This planetary motion provides two major functions for performing CCC separation. The fi rst is a rotary-seal-free elution system so that the mobile phase is continuously eluted through the rotating separation column. • The second and more important function is that it produces a unique hydrodynamic motion of two solvent phases within the rotating multilayer coiled column mainly due to the Archimedean screw effect. 13.3 HSCCC Instrument and Mechanism Figure 4: High speed counter-current chromatography instrument When two immiscible solvent phases are introduced in an endclosed coiled column, the rotation separates the two phases completely 215

13 COUNTER-CURRENT CHROMATOGRAPHY<br />

13.2.4 Applications of Droplet Counter-current<br />

Chromatography<br />

This simple DCCC instrument has been used to per<strong>for</strong>m effi<br />

cient preparative separations such as:<br />

• Separation of non-polar compounds.<br />

• Isolation of virginiamycin-M1 <strong>and</strong> parthenolide.<br />

• Isolation of vitamin B12.<br />

• Pharmacognostical studies of Tabernaemontana species:<br />

ion-pair DCCC of indole alkaloids from suspension cultures.<br />

• Chiral resolution of a carboxylic acid.<br />

• Separation of natural polar substances by reverse phase<br />

HPLC, centrifugal thin layer chromatography <strong>and</strong> DCCC.<br />

• Effi cient isolation of ecdysteroids from the silkworm, Bombyx<br />

mori.<br />

• Analytical DCCC isolation of 20-hydroxyecdysone from Vitex<br />

thyrsifl ora (Verbenaceae).<br />

• Increasing the speed of DCCC separations.<br />

• Complete resolution of isoleucine.<br />

• DCCC of anthocyanins.<br />

• Effi cient isolation of phytoecdysones from Ajuga plants by<br />

high-per<strong>for</strong>mance liquid chromatography <strong>and</strong> DCCC.<br />

• DCCC with non-aqueous solvent systems.<br />

• Use of DCCC in log P determinations.<br />

• Purifi cation of Stevia rebaudiana sweet constituents (potential<br />

sweetening agent of plant origin).<br />

• Water-free solvent system <strong>for</strong> DCCC <strong>and</strong> its suitability <strong>for</strong> the<br />

separation of non-polar substances.<br />

• Isolation of phorbol, 4α-phorbol <strong>and</strong> croton oil.<br />

• Purifi cation of antibiotics such as gramicidins, tyrocidines<br />

<strong>and</strong> tetracyclines.<br />

13.2.5 Limitations of DCCC<br />

• Extremely low fl ow rates (sometimes solute retention is<br />

measured in days).<br />

• Only biphasic solvents systems that <strong>for</strong>m stable droplets<br />

can be used.<br />

• Poor mixing of phases, which results in relatively low effi -<br />

ciency.<br />

13.2.6 Modern Counter-current Chromatography<br />

Modern CCC has split into two basic directions. The fi rst, which<br />

is called High-speed Counter-current Chromatography (HSCCC), uses an apparatus<br />

with a variable gravity fi eld produced by a double axis gyratory motion<br />

(Figure 4). The second, termed Centrifugal Partition Chromatography<br />

214

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