Seeding anti-solvent

Gas anti-solvent fractionation was carried out using C02 on mixtures of lecithin/Soya oil/hexane coriander seed triglycerides/essential oil/hexane and pure components of the mixtures. Separation of the mixtures into individual components was demonstrated at a laboratory scale. The degree of separation possible was a function of the volume expansion of the liquid solvent phase. The pressure/volume expansion at which a pure component precipitated was qualitatively related to its solubility in supercritical C02. The volume expansion was a function of temperature and pressure. The pressure required to reach a certain volume expansion increased as both the temperature and triglyceride content increased. 

The requirement for increased amounts of seed for reactive crystallization compared with the cooling, evaporahon, and anti-solvent methods is discussed by Mullin (2001, p. 339). Amounts of seed up to 50% are indicated to be necessary in recycle systems to provide the seed area necessary. The requirement for this increased amount is the direct result of the rapid development of supersaturation by reaction and the need to have sufficient surface area for growth throughout the operation, especially at the start of reagent addihon. 

A commonly used protocol used in controlling crystallization processes is to establish a seed bed prior to the bulk crystallization process. This significantly aids in the reproducibility of the crystallization. This is effected by determining the saturation point of the system and then adding authentic product prior to reaching this point. Once the seed bed is maintained, the system by default has been saturated with the desired product and by either addition of anti-solvent or with controlled cooling, both nucleation and crystal growth can be controlled. 

Pyrrolizidine alkaloids have long been known to be antitumor active and, more recently, have become of interest as anti-cancer agents. They occur naturally in several plant species, but are often difficult to extract and isolate from the plant material without degradation or the use of toxic solvents. The extraction of a model pyrrolizidine alkaloid, monocrotaline, from the seeds of Crotalaria spectabilis was investigated in this work. 

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