Possibility for application of liquefied gases for purification of Barberry alkaloids

Abstract

Introduction. Biologically active substances (BAS) of barberry roots represented by alkaloids of isoquinoline group are perspective substances for development of preparations with multiple pharmacological activities. However, now manufacture of them in Ukraine is stopped. One of the reasons of thisis out-of-date production technologies of alkaloids involving use of toxic and/or flammablesolvents. In the article possibility for application of liquefied gases in technology of obtaining of alkaloids from barberry roots has been studied.Materials and methods. Initial raw herb drug were barberry (Berberis vulgaris) roots harvestedin spring on the territory of Southern Ukraine. Theirmoisture content was 11%, comminuting degreewas 0,5-1,4 mm. At the first stage purificationof raw herb drug from lipophilic impurities(defatting) was made with use of some liquefied gases: tetrafluoroethane, isobutane, difluorochloromethaneand difluoromethane. Extraction of the alkaloid sum was made with difluoromethane mixed with various quantities of liquid ammonia or diethylamine as alkaline agent. Crudeextracts were exposed to two-level liquefied-gas purification. At firstthe alkaloid bases were transformed into saline forms with aqueous solutions of acids and purified from ballast impurities with liquefied freon-22. Then alkaloid salts were reextracted from aqueous phase in the base form with liquefied mixture of difluoromethane and ammonia. Mixing of liquid phases was provided by creation of alternategradients of temperatures and, as consequence, pressures between separators feedingalternately cool water into jacket of one of them, and warm water – into jacket of another one. Quantity of lipophilic ballast impurities and also weight of extractives were determined gravimetrically. Quantitativeanalysis of the alkaloid sum was made by titrimetric method after sedimentation of alkaloids with volumetric solution of phosphomolybdic acid.Results and discussion.It has been found that at stage of degreasing of raw crude drug the most selective solvent to lipophilic ballast compounds was isobutaneand difluorochloromethane, but the latter was more rational for using in industrial scale concerning its fire-safety and economicavailability. It has been also found that efficiency of the purification stage of Berberis alkaloids appreciablydependson composition of extracting solvent while obtaining of crude extracts. The best parameters in the finished product have been revealed after purification of the extracts obtained with difluoromethane containing 12% of liquid ammonia: quantity of BAS (alkaloids) in the finished product reached95%, and their losses were insignificant– 3,5%.Increasing of cosolvent (ammonia) content in the extracting solvent considerably complicatedpurification of extractives, and losses of alkaloids raised to 13,2%, obviously as a result of presence of considerable quantity of hydrophylic ballastsubstances. Reducing of the ammonia content in the extracting solvent down to 1% also caused negativeimpact on process of obtaining of the alkaloids which yield was the lowest amonginvestigated assays. It’s possible to explain this by lower рН value in extractingmedium, change of solvent polarity, therefore middle-polar and hydrophobiccompounds preferably passed into composition of crude extracts. Conclusions. Acceptability for use of liquefied gases and their mixtures for purification of the alkaloid sum from barberry roots has been proved. It has been shown that prior to stage of extraction of these BAS it’s expedient to withdraw lipophilic impurities from the crude herbal drug with liquified difluorochloromethane (freon-22). Purification efficiency of the finished product considerably depends on composition of extracting solvent during obtaining of crude extracts. The best parameters were found after purification of the extracts taken with difluoromethane containing 12% of liquid ammonia. It’s the most expedient to purify crude extracts by two-step procedure using on the first step liquefied difluorochloromethane (freon-22) as organic phase and on the second one – difluoromethane mixed with 10% of ammonia, and as aqueous phase – 10 % acidic solutions; at the second step it’s necessary to provide liquid re-extraction of the alkaloid bases in triplicate.