Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1996-01-11
1997-11-04
Higel, Floyd D.
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
514397, C07G 500, C07D40506
Patent
active
056841558
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Field of the Invention
The present invention relates to a process for the extraction and purification of alkaloids from plant materials and tissues.
In particular, the invention relates to a process for the extraction and purification of pilocarpine from leaves of Pilocarpus Microphillus.
2. Description of the Prior Art
The presently known processes for the extraction of the alkaloids from plant materials (leaves, roots and so on) are based on the use of either polar organic solvents, such as methil alcohol, ethil alcohol, chlorinated solvents and the like, or non-polar organic solvents, such as benzene, toluene and the like, that are contacted with the starting plant material previously treated with aqueous sodium carbonate, aqueous ammonia or other alkalinizing substances suitable of converting the alkaloid from the form in which it is linked to the tissues to a free base soluble in the organic solvents.
The organic extract thus obtained contains considerable amounts of chlorophille and other natural compounds present in the plant material that greatly hinder the subsequent phases of extraction and purification of the alkaloid.
The process conditions (high pH, hot extraction, long stay of the drug in the extractor, etc.) greatly favour the isomerization of some alkaloids, such as for instance in the case of pilocarpine, a part of which in such conditions is changed into isopilocarpine, which is uneffective from the pharmacological point of view.
Furthermore, the high amount of the solvent used (more than 6 times the weight of the raw material to be extracted) requires expensive operations for the recovery of the same.
According to the known processes, the alkaloid is then extracted from the organic solvent with aqueous solutions of mineral acids, whereby it is transformed from a free base into a salt soluble in an aqueous solution of the used acid, or it is recovered as free base by complete evaporation of the solvent.
U.S. Pat. No. 3,631,059 discloses a process where the alkaloid is extracted from the plant material by using a diluted aqueous solution of a strong mineral acid or a strong organic acid, neutralizing then the acid aqueous extract to a pH between 5 and 13 and adsorbing the alkaloid on activated carbon, separating the carbon by which the alkaloid has been adsorbed from the exhausted solution and finally eluting the alkaloid with an aqueous solution of a strong mineral acid or a strong organic acid. In this type of process the aqueous extracts resulting from the extraction with diluted acid solutions contain various types of impurities coming from the plant (chlorophille and other pigments, sugars, starch, proteins, tannin, fat, etc.) which cannot be removed either by filtration or by strong centrifugation. Such impurities lead to a quick exhaustion of he carbon and also, after the alkalinization, give rise to stable emulsions which make extremely difficult the subsequent phases of the process. In the last analysis, the process according to the above mentioned U.S. patent, though providing an alternative to the use of organic solvents for the extraction of alkaloids from plant tissues, is however not workable in practice due to the above described incoveniences.
The purpose of the present invention is to provide a process for the extraction and purification of alkaloids from plant tissues and plant materials in general, which would be suitable from one side to take advantage from the extraction with aqueous acid solutions instead of with organic solvents and, from the other side, be effective and workable at industrial level.
SUMMARY OF THE INVENTION
The novel features of the process according to the invention consist in that for the clarification of the extract there is provided for the addition of coagulative agents with a consequent flocculation and sedimentation of the suspended impurities the concentration of said agents in said extract being at least 2 g/l. Moreover, the extraction of the alkaloid from the clarified extract comprises either of the following operation:
REFERENCES:
patent: 3631059 (1971-12-01), Goorley et al.
patent: 4045558 (1977-08-01), Smith et al.
patent: 4076942 (1978-02-01), Smith et al.
patent: 5025027 (1991-06-01), Rapoport et al.
patent: 5059531 (1991-10-01), Reuter
Burchianti Gilberto
Burchianti Marcello
Correa Viana Claudio Luiz
Falcao De Andrade Francisco Jose
Rocha De Albuquerque Lucio Elisabeth Maria
Higel Floyd D.
Polis A.G.
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