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The Infrared Drying of Pharmaceutical Extracts
The Infrared Drying of Pharmaceutical Extracts* By S. COLLETT Infrared drying has been applied t o more than forty samples of botanical drugs and extracts. Deterioration during the drying time of fifty minutes was slight, and drying was complete i n that period of time.
a dry extract can be defined as a solution of the active principles of a vegetable drug which has been evaporated to dryness. The preparation of such extracts, especially on the large scale, is by no means such a simple matter as the above definition might imply, however; the thermolabile nature of many drug constituents necessitates that the most careful attention be paid to the conditions under which the evaporation is carried out. The manufacture of dry extracts usually fnvolves the following stages: ( a ) the extraction of the vegetable drug (in most cases by percolation) with a suitable solvent (almost invariably water, alcohol, or a mixture of the two) ; ( b ) the evaporation of the resulting aqueous or alcoholic liquor to a soft extract (usually rarricd out in a vacuum still); (c) the drying of the soft extract, to produce a friable solid; (a) the reduction of the latter to powder or to granules. While part ( b ) aboGe can, with very little difficulty, be accomplished at temperatures of 50" or less, the final drying of the soft extract t o a solid involves (at least in its later stages) te*peratures in the region of 100-115"; and it is here, in stage (c) of manufacture, that most damage is done ta any thermolabile substances present in the ebtract. I n certain instances, such as belladonna and hyoscyamus extracts, the damage may lie assessed by assaying the material for qlkaloidal content before and after stage (c), since any deterioration due to excessive heat results inevitably in a loss of alkaloid. When dealing with nonalkaloidal extracts, excessive heating during manufacture can almost invariably be detected by determining the proportion of insoluble matter in the finished product and comparing i t with that present in the soft extract. In such cases, the dry extract is found to contain a considerably higher percentage of insoluble matter than was present in the intermediate product. The conversion of soft extract to dry is usually done in a vacuum oven, which generally has hollow steam-heated shelves upon which are placed metal trays, with devices for controlling vacuum
G
E N E R ~ L L Y SPEAKING,
*Received England.
October 9, 1851, from Subdwy, SufIolk.
and steam pressure, and with inspection windows through which the inaterial may be observed throughout the drying process. Although it would appear that other methods of drying have been tried, a t least on the experimental scale, most of them have received only brief mention in the pharmaceutical literature. The literature does not include any account of any quantitative investigation into the changes brought about in the material being dried by such processes. During the course of recent researches into the use of infrared radiation in moisture determination, certain chance observations led to the belief that the majority of vegetable extracts would undergo comparatively little deterioration during infrared drying; and i t was thought that, if this were the case, a quantitative examination of such extracts before and after drying would yield interesting results. I n consequence, some forty samples, each representing a different batch of extract, were infrared dried on a small scale and the solid products immediately transferred to small airtight containers. Portions of the original soft extract and of the dried product were analyzed with a view to assessing what deterioration had occurred as a result of exposure to infrared radiation. Details of these experiments and their results are given in the following paragraphs. EXPERIMENTAL Undried Soft Extract Each sample was tested for moisture content and for insoluble matter, as follows: Moisture.-Five grams of the material was infrared dried to constant weight, the loss in weight being equivalent to the moisture (or volatile matter) present in the original sample. The result was expressed as a percentage. Insoluble Matter.-Two grams of extract was weighed on a small tared paper and transferred to a weighed centrifuge tube. To it was added 10-15 1111. of the appropriate solvent (i. e.. that which was originally employed in the preparation of the extract from the crude drug), and the tube and cow tents were then carefully warmed by immersion in a steam bath (in the case of alcoholic extracts it was vital that excessive heating be avoided, because of any resulting alteration in alcohol strength). At frequent intervals, the tube was rolled between the hands in order to promote intimate mixing of the warm, softened extract with the solvent and so effect solution. In a few cases it was necessary, owing to the extra-stiff nature of the sample, to stir with a
476
SCIENTIFIC EDITION
September. 1952
glass rod. Meanwhile the paper on which the sample was weighed was removcd from thc tube with the aid of forceps. When as much as possible of the extract had dissolved, the solution was Centrifuged for four to five minutes and the liquid was poured off. Any residue in the tube was washed with an additional 10 ml. of the solvent, centrifuged again for four to five minutes, and the liquid was again poured off. The tube, with any insoluble rcsidue, was finally dried to constant weight a t 100’. Preparation of Dry Extract A quantity of extract was spread in an even layer, about l / l 0 of an inch in thickness, on an aluminum pan. The latter was then placed beneath a 400watt infrared lamp a t a distance of about 12 cm. and left there until the material attained constant weight; i. e., until all moisture had been removed. The resulting brittle mass was immediately removed from the pan, rapidly powdered, and transferred to an airtight container. Analysis of Product The infrared dried material was examincd for insoluble matter by the same method employed for the soft extract; the initial weighing was accomplished with the greatest possible speed in view of the deliquescent nature of the material. Results The results obtained with the various extracts before and after infrared drying are recorded in Table I. In addition to the expcrimental results, there is recorded for each sample the calculated theoretical insolublc-matter contcnt of thc dry extract. This value represents the proportion of insoluble matter which would be present in the dried material if no additional insoluble matter was produced during the drying process, and is calculated from the formula: Theoretical amount insoluble
=
I x 100 (100 - M )
where I is the percentage of insoluble matter present in the original soft extract and M is its moisture content As will be observed, the choice of material for this investigation was not confined particularly to those extracts which appear in the dry form commercially; the samples were chosen solely with a view to providing as wide a range of drug constituents as possible.
.
DISCUSSION Taken as a whole, the results are distinctly encouraging, in that the deterioration resulting from the infrared drying is relatively small in the majority of cascs. Out of a total of 43 samples, 28 of them experienced an increase in insoluble matter contcnt of less than 1%, calculated on the dried material. Moreover, in no case did the drying process bring about any appreciable degree of darkening or other discoloration. In regard to the physical properties of the dried products, all but two of the latter could be quite easily powdered. As might be expected, however, the powders werc at1 extremely deliquescent: in somc
477
cases, even a few seconds’ exposure to the atmosphere sufliced to bring about some degree of caking. Storage in nearly full, airtight containers, however, served to prevent any such caking, and under these conditions the powdered extracts retained their freeflowing properties for long periods. This was demonstrated, after completion of analytical tests, by storing the powders in heat-sealed glass ampuls for several months and examining them visually a t intervals. Drying Time and Temperature Under the conditions outlined, the time requircd for complete infrared drying varied between thirty and fifty minutes; longer periods would, of course, be necessary if thicker layers of extract were to be dried. Needless to say, that is one of the factors which would call for careful consideration in attempting to step up this mode of drying to the large scale. The maximum temperature attained during drying was 80”, as comparcd with maxima of 100-llOo in vacuum oven drying. Moreover, it must be remembered that, even in the case of the longestdrying extracts, the material was subjected to 80” for only about one quarter of the total drying time, possibly less. The Egect o n Individual Constituents In view of the encouraging results obtained in the experiments so far described, it was felt that some further data, illustrating the effect of infrared drying on individual active constituents, would be of interest. Four of the extracts mentioned in Table I were assayed for their principal constituents; the corresponding infrared dried samples were similarly assayed, and the results compared with “theoretical” values calculated in a manner similar to those appearing in Table I. The alcoholic extracts of kola, licorice, nux vomica, and hydrastis wcrc chosen for this purpose, and the assay methods employed in each case are now briefly outlined. Determination of Caffeine in Kola Extracts One gram of sample was mixed with approximately 5 Gm. of calcium hydroxide and 5 Gm. of kieselguhr and the mixture wa6 moistened with water to form a smooth paste. The latter was then carefully heated on a steam bath until converted into a friable mass, which was next exhaustively extracted with hot chloroform. The chloroforrnic extract, after filtration, was evaporated to dryness, and the residue dissolved in 2 ml. of fresh chloroform. To this was added 1.5 ml. of hot water, the mixture was boiled for five minutes, and the hot aqueous solution was filtered into a tared dish. Residue and filter were washed with three 10-ml. portions of hot water which was then added to the tared dish. The mixed aqueous filtrates were then evaporated to dryness and the residue of caffeine was dried t o constant weight at 100’. The caffeine content was calculated as a percentage. Determination of Strychnine in Nux Vomica Extracts The method used was that of the €3. P. 1948, 3 Gm. of sample being tested in each case. The B. P.
178
JOTJRNAL OF 1Ill3
AMERICANPIIARMACEUTICAL AssocrAnoN
procedure involves the production of a chloroformic solution of the total alkaloids, removal of the solvent by distillation, treatment of the alkaloidal residue with nitric acid to destroy the brucine, and the ex-
TABLE I.-RESUI,TS OBTAINED BEFORE INFRARED DRYIN@ .-
~~~~~~
---
Moisture.
%
Cascara Leptandra UvaeUrsi(+) Buchu(+) Cascara(+) Cascara Licorice Licorice(+) Convallaria
25.3 18.5 18.8 27.0 28.7 25.0 15.6 23.5
(+I
(+I
Hamamelis Hamamelis Viburnum Valerian Gentian (+) Coltsfoot (+) Kola ( 1 Kola Krameria (+) Senna fruct (+) Hawthorn Grindelia Horehound
+
(+)
Cornsilk (+) Anthemidis (+) Pichi herb (+) Burdock Foenugr eek Damiana ( ) Cascara Senna leaf Fucus vesic(+) Euphorbia Sarsauarilla Belladonna root Belladonna leaf Melilotus Melilotus Nux vomica Valerian ( ) Lupulus Bitter orange Rheum Hydrastis
+
+
-
~
Extract
AND AFTER
Insol. Matter, % Before After Drying Drying
%
3.6 2.4 1.35 2.4 0.25 1.7
2.4 1.15 3.95 5.0 3.6 4.1 2.0 2.8
0.7 0.5 4.4 3.3 1.9 3.2 0.29 2.2
21.6 18.8
2.35 2.47
3.1 5.9
3.0 3.0
26.0 20.2 19.8 ~. 20.0 18.6 20.0 22.0 52.0
2.25 1.1 1.4 3.0 1.2 2.6 1.7 9.6
4.8 1.4 9.3 4.0 3.0 3.8 2.5 27.1
3.0 1.37 1.75 3.7 . 1.4 3.2 2.2 20.0
25.2 10.2 26.0
2.55 2.5 2.6
3.7 2.9 4.6
3.4 2.8 3.45
18.8 16.0
2.15 1.8
3.1 2.15
2.6 2.1
20.0 31.6 27.5 22.0 40.5 17.6 23.4
1.9 6.3 3.1 1.2 5.1 0.75 0.7
2.65 9.0 4.24 1 .8 9.2 2.3 1.1
2.5 9.1 4.27 1.54 8.5 0.91 0.91
23.4 19.0 18.5
2.25 3.0 1.5
4.0 3.9 3.5
2.93 3.7 1.84
20.0
4.0
6.0
5.0
3.3 0.75 2.25 0.5 1.3 2.7 2.6
4.9 1.5 4.6 1.2 2.6 4.2 3.3 3.1 1.4
4.1 0.91
~
20.0 18.0 21.5 20.0 22.0 21.0 18.5 22.5 20.3
0.5
Theoretical Amt. Insol.,
0.4
1.8
0.8
+ were aqueous extracts;
a Samples marked were alcoholic extracts
2.86
0.62 1.66 3.4 3.22 2.3 1.0 remainder
Vol. XLI, NO.9
traction of the strychnine (after making alkaline) with fresh chloroform. After removal of the solvent, the alkaloid is finally dissolved in alcohol and estimated titrimetrically. Determination of Hydrastine in Hydrastis Extracts Two grams of sample, dissolved in 10 ml. of 70% alcohol, was transferred to a 100-ml. graduated flask;. 20 rnl. of potassium iodide solution was added, the mixture adjusted to 100 ml. with water, and the flask shaken for several minutes. A portion of 50 ml. of the mixture was filtered off, made alkaline with ammonia, and extracted by shaking with three separate 30-1111. portions of ether. The mixed ethereal extracts were filtered into a tared h s k , the ether was removed by distillation, and the residue was dried to constant weight a t 80". The iinal weight represents the hydrastine from 1 Gm. of sample. Determination of Glycyrrhizin i n Licorice Extracts Two grams was dissolved in a few milliliters of water, and the solution was treated with twice its volume of 95% alcohol to precipitate unwanted gummy matter. The liquid was clarified by centrifuging, and the precipitate was washed with a few milliliters of 70% alcohol; the washings were then centrifuged and added to the main liquid. The mixture was vacuum-distilled to dryness, and the residue was dissolved in a few milliliters of water. The aqueous solution was transferred to a centrifuge tube, twice the volume of dilute sulfuric acid was added, and the mixture was centrifuged. The liquid was poured off from the glycyrrhizin precipitate which was then dissolved in dilute ammonia; the ammonia1 solution was filtered into a tared dish, evaporated to dryness, and the residue was dried to constant weight at 100" Results of Assays The results obtained from the above assays are summarized in Table 11. It will be observed that the percentage of active constituent lost during drying, calculated in terms of the dried extract, was in no instance greater than 5% (i. e., 5% of that present in the original material); this amply supports the evidence obtained in the earlier experiments that, under the specified conditions, the drying of extracts by means of infrared radiation results in the majority of cases in only a small degree of deterioration, as shown by "insoluble matter" determinations. I t should, perhaps, be emphasized that no attempt was made during this investigation to stcp up the infrared drying of extracts to the large scale or to solve any of the chemical engineering problems which would inevitably arise. The author has only a few data relating to the effect of vacuum-oven drying on the insoluble-
TABLE 11 Extract
Active Constituent
Before Drying, %
After Drying. %
Theoretical Value, %
Kola Nux vomica Hydrastis Licorice
Caffeine Strychnine Hydrastine Glycyrrhizin
6.8 6.2 7.8 26.5
8.53 7.63 9.26 30.4
8.7 7.75 9.75 31.3
Recovery,
%
98 98.5 95 97
September, 1952
SCIENTIFIC EDITION
479
TABLE IIr
o
Moisture, Extract
%
Initial Insol., %
Final Insol., %
Theoretical Value, %a
Cascara Aqueous Cascara Aqueous Krameria Aqueous Valerian Aqueous C.nlerian Aqueous
20 24 30 28 21
2.5 2.2 3.4 4.7 1.8
9.2 8.1 15.7 14.3 11.6
3.1 2.9 4.8 6.3 2.8
A w ~ m i n gno inrrease during drying
matter content of the product. The srnall amourtt of information which is available is suiiininrized in Table 111. SUMMARY
The infrared drying of pharmaceutical extracts has been investigated on the laboratory scale. More than forty different samples were dried by this means, and the proportion of insoluble matter was determined in the undried and dried material in each case. By comparing the figures thus obtained before and after drying, it is shown that in the ma-
jority of cases the deterioration which occurs duririfi the drying process is slight. This conclusion is further supported by the results o f some additional experiments, carried out on four of the samples, in which the undried and dried extracts were each assayed for a particular active constituent. None of the samplcs examined required more than fifty minutes' exposure to the infrared radiation; complete drying was invariably effected within that period. The maximum teniperature reached by the material being dried was 80".
A Method for the Differentiation of Hydroxocobalamin from Cyanocobalamin Employing the Ascorbic Acid Reaction* By J. A. CAMPBELL, J. M. McLAUGHLAN, and D. G. CHAPMANt,f The fact that hydroxocobalamin is readily destroyed in solutions containing ascorbic acid while cyanocobalarnin is relatively stable in such solutions has been used as the basis of a procedure to determine hydroxocobalamin in the presence of cyanocobalarnin. The method is simple, and appears to be specific and reliable. OLLOWING earlier work (1, 2) on the reaction Fof vitamin BIP and ascorbic acid, Trenner, et al. (3), reported in 1950 that vitamin Biza (hydroxocobalamin) was readily destroyed in
* Received June 3, 1952, from the Food and Drug Divi sions, Department of National Health and Welfare, Ottawa, Canada. t The authors are indebted to Dr. H H. Fricke, Abbott Laboratories, Chicago, and to Dr. G. E. Boxer. Merck & C o . , Rahway, N . J., for generous supplies of vitamin BLL and Btna respectively. After this work was completc=d. the authors were privileged, through the kindness of Dr. D. V. Frost, Abbott Laboratories. to see the draft of a paper outlining experience in their laboratory with this reaction. The data reported here confirm some of their work.
solutions containing ascorbic acid, and that vitamin B12 (cyanocobalamin) was relatively stable under such conditions. The reaction appeared to be influenced by PH. These data suggested a possible means of differentiating between hydroxocobalamin and cpanocobalamin, using .a microbiological assay as the basis for the test. In 1950, Frost, et ui. (4),reported experience with such a procedure where measurements were made of vitamin By. potency before and after destruction of the vitamin BIZb(hydroxocobalamin) with sodium ascorbate. They also described other factors affecting the reaction, but no details of the method were published. Independent work in this laboratory has led to the development of a somewhat similar method for the differential estimation of vitamins BI2, and B12a in the presence of vitamin Bit. Vita-
a dry extract can be defined as a solution of the active principles of a vegetable drug which has been evaporated to dryness. The preparation of such extracts, especially on the large scale, is by no means such a simple matter as the above definition might imply, however; the thermolabile nature of many drug constituents necessitates that the most careful attention be paid to the conditions under which the evaporation is carried out. The manufacture of dry extracts usually fnvolves the following stages: ( a ) the extraction of the vegetable drug (in most cases by percolation) with a suitable solvent (almost invariably water, alcohol, or a mixture of the two) ; ( b ) the evaporation of the resulting aqueous or alcoholic liquor to a soft extract (usually rarricd out in a vacuum still); (c) the drying of the soft extract, to produce a friable solid; (a) the reduction of the latter to powder or to granules. While part ( b ) aboGe can, with very little difficulty, be accomplished at temperatures of 50" or less, the final drying of the soft extract t o a solid involves (at least in its later stages) te*peratures in the region of 100-115"; and it is here, in stage (c) of manufacture, that most damage is done ta any thermolabile substances present in the ebtract. I n certain instances, such as belladonna and hyoscyamus extracts, the damage may lie assessed by assaying the material for qlkaloidal content before and after stage (c), since any deterioration due to excessive heat results inevitably in a loss of alkaloid. When dealing with nonalkaloidal extracts, excessive heating during manufacture can almost invariably be detected by determining the proportion of insoluble matter in the finished product and comparing i t with that present in the soft extract. In such cases, the dry extract is found to contain a considerably higher percentage of insoluble matter than was present in the intermediate product. The conversion of soft extract to dry is usually done in a vacuum oven, which generally has hollow steam-heated shelves upon which are placed metal trays, with devices for controlling vacuum
G
E N E R ~ L L Y SPEAKING,
*Received England.
October 9, 1851, from Subdwy, SufIolk.
and steam pressure, and with inspection windows through which the inaterial may be observed throughout the drying process. Although it would appear that other methods of drying have been tried, a t least on the experimental scale, most of them have received only brief mention in the pharmaceutical literature. The literature does not include any account of any quantitative investigation into the changes brought about in the material being dried by such processes. During the course of recent researches into the use of infrared radiation in moisture determination, certain chance observations led to the belief that the majority of vegetable extracts would undergo comparatively little deterioration during infrared drying; and i t was thought that, if this were the case, a quantitative examination of such extracts before and after drying would yield interesting results. I n consequence, some forty samples, each representing a different batch of extract, were infrared dried on a small scale and the solid products immediately transferred to small airtight containers. Portions of the original soft extract and of the dried product were analyzed with a view to assessing what deterioration had occurred as a result of exposure to infrared radiation. Details of these experiments and their results are given in the following paragraphs. EXPERIMENTAL Undried Soft Extract Each sample was tested for moisture content and for insoluble matter, as follows: Moisture.-Five grams of the material was infrared dried to constant weight, the loss in weight being equivalent to the moisture (or volatile matter) present in the original sample. The result was expressed as a percentage. Insoluble Matter.-Two grams of extract was weighed on a small tared paper and transferred to a weighed centrifuge tube. To it was added 10-15 1111. of the appropriate solvent (i. e.. that which was originally employed in the preparation of the extract from the crude drug), and the tube and cow tents were then carefully warmed by immersion in a steam bath (in the case of alcoholic extracts it was vital that excessive heating be avoided, because of any resulting alteration in alcohol strength). At frequent intervals, the tube was rolled between the hands in order to promote intimate mixing of the warm, softened extract with the solvent and so effect solution. In a few cases it was necessary, owing to the extra-stiff nature of the sample, to stir with a
476
SCIENTIFIC EDITION
September. 1952
glass rod. Meanwhile the paper on which the sample was weighed was removcd from thc tube with the aid of forceps. When as much as possible of the extract had dissolved, the solution was Centrifuged for four to five minutes and the liquid was poured off. Any residue in the tube was washed with an additional 10 ml. of the solvent, centrifuged again for four to five minutes, and the liquid was again poured off. The tube, with any insoluble rcsidue, was finally dried to constant weight a t 100’. Preparation of Dry Extract A quantity of extract was spread in an even layer, about l / l 0 of an inch in thickness, on an aluminum pan. The latter was then placed beneath a 400watt infrared lamp a t a distance of about 12 cm. and left there until the material attained constant weight; i. e., until all moisture had been removed. The resulting brittle mass was immediately removed from the pan, rapidly powdered, and transferred to an airtight container. Analysis of Product The infrared dried material was examincd for insoluble matter by the same method employed for the soft extract; the initial weighing was accomplished with the greatest possible speed in view of the deliquescent nature of the material. Results The results obtained with the various extracts before and after infrared drying are recorded in Table I. In addition to the expcrimental results, there is recorded for each sample the calculated theoretical insolublc-matter contcnt of thc dry extract. This value represents the proportion of insoluble matter which would be present in the dried material if no additional insoluble matter was produced during the drying process, and is calculated from the formula: Theoretical amount insoluble
=
I x 100 (100 - M )
where I is the percentage of insoluble matter present in the original soft extract and M is its moisture content As will be observed, the choice of material for this investigation was not confined particularly to those extracts which appear in the dry form commercially; the samples were chosen solely with a view to providing as wide a range of drug constituents as possible.
.
DISCUSSION Taken as a whole, the results are distinctly encouraging, in that the deterioration resulting from the infrared drying is relatively small in the majority of cascs. Out of a total of 43 samples, 28 of them experienced an increase in insoluble matter contcnt of less than 1%, calculated on the dried material. Moreover, in no case did the drying process bring about any appreciable degree of darkening or other discoloration. In regard to the physical properties of the dried products, all but two of the latter could be quite easily powdered. As might be expected, however, the powders werc at1 extremely deliquescent: in somc
477
cases, even a few seconds’ exposure to the atmosphere sufliced to bring about some degree of caking. Storage in nearly full, airtight containers, however, served to prevent any such caking, and under these conditions the powdered extracts retained their freeflowing properties for long periods. This was demonstrated, after completion of analytical tests, by storing the powders in heat-sealed glass ampuls for several months and examining them visually a t intervals. Drying Time and Temperature Under the conditions outlined, the time requircd for complete infrared drying varied between thirty and fifty minutes; longer periods would, of course, be necessary if thicker layers of extract were to be dried. Needless to say, that is one of the factors which would call for careful consideration in attempting to step up this mode of drying to the large scale. The maximum temperature attained during drying was 80”, as comparcd with maxima of 100-llOo in vacuum oven drying. Moreover, it must be remembered that, even in the case of the longestdrying extracts, the material was subjected to 80” for only about one quarter of the total drying time, possibly less. The Egect o n Individual Constituents In view of the encouraging results obtained in the experiments so far described, it was felt that some further data, illustrating the effect of infrared drying on individual active constituents, would be of interest. Four of the extracts mentioned in Table I were assayed for their principal constituents; the corresponding infrared dried samples were similarly assayed, and the results compared with “theoretical” values calculated in a manner similar to those appearing in Table I. The alcoholic extracts of kola, licorice, nux vomica, and hydrastis wcrc chosen for this purpose, and the assay methods employed in each case are now briefly outlined. Determination of Caffeine in Kola Extracts One gram of sample was mixed with approximately 5 Gm. of calcium hydroxide and 5 Gm. of kieselguhr and the mixture wa6 moistened with water to form a smooth paste. The latter was then carefully heated on a steam bath until converted into a friable mass, which was next exhaustively extracted with hot chloroform. The chloroforrnic extract, after filtration, was evaporated to dryness, and the residue dissolved in 2 ml. of fresh chloroform. To this was added 1.5 ml. of hot water, the mixture was boiled for five minutes, and the hot aqueous solution was filtered into a tared dish. Residue and filter were washed with three 10-ml. portions of hot water which was then added to the tared dish. The mixed aqueous filtrates were then evaporated to dryness and the residue of caffeine was dried t o constant weight at 100’. The caffeine content was calculated as a percentage. Determination of Strychnine in Nux Vomica Extracts The method used was that of the €3. P. 1948, 3 Gm. of sample being tested in each case. The B. P.
178
JOTJRNAL OF 1Ill3
AMERICANPIIARMACEUTICAL AssocrAnoN
procedure involves the production of a chloroformic solution of the total alkaloids, removal of the solvent by distillation, treatment of the alkaloidal residue with nitric acid to destroy the brucine, and the ex-
TABLE I.-RESUI,TS OBTAINED BEFORE INFRARED DRYIN@ .-
~~~~~~
---
Moisture.
%
Cascara Leptandra UvaeUrsi(+) Buchu(+) Cascara(+) Cascara Licorice Licorice(+) Convallaria
25.3 18.5 18.8 27.0 28.7 25.0 15.6 23.5
(+I
(+I
Hamamelis Hamamelis Viburnum Valerian Gentian (+) Coltsfoot (+) Kola ( 1 Kola Krameria (+) Senna fruct (+) Hawthorn Grindelia Horehound
+
(+)
Cornsilk (+) Anthemidis (+) Pichi herb (+) Burdock Foenugr eek Damiana ( ) Cascara Senna leaf Fucus vesic(+) Euphorbia Sarsauarilla Belladonna root Belladonna leaf Melilotus Melilotus Nux vomica Valerian ( ) Lupulus Bitter orange Rheum Hydrastis
+
+
-
~
Extract
AND AFTER
Insol. Matter, % Before After Drying Drying
%
3.6 2.4 1.35 2.4 0.25 1.7
2.4 1.15 3.95 5.0 3.6 4.1 2.0 2.8
0.7 0.5 4.4 3.3 1.9 3.2 0.29 2.2
21.6 18.8
2.35 2.47
3.1 5.9
3.0 3.0
26.0 20.2 19.8 ~. 20.0 18.6 20.0 22.0 52.0
2.25 1.1 1.4 3.0 1.2 2.6 1.7 9.6
4.8 1.4 9.3 4.0 3.0 3.8 2.5 27.1
3.0 1.37 1.75 3.7 . 1.4 3.2 2.2 20.0
25.2 10.2 26.0
2.55 2.5 2.6
3.7 2.9 4.6
3.4 2.8 3.45
18.8 16.0
2.15 1.8
3.1 2.15
2.6 2.1
20.0 31.6 27.5 22.0 40.5 17.6 23.4
1.9 6.3 3.1 1.2 5.1 0.75 0.7
2.65 9.0 4.24 1 .8 9.2 2.3 1.1
2.5 9.1 4.27 1.54 8.5 0.91 0.91
23.4 19.0 18.5
2.25 3.0 1.5
4.0 3.9 3.5
2.93 3.7 1.84
20.0
4.0
6.0
5.0
3.3 0.75 2.25 0.5 1.3 2.7 2.6
4.9 1.5 4.6 1.2 2.6 4.2 3.3 3.1 1.4
4.1 0.91
~
20.0 18.0 21.5 20.0 22.0 21.0 18.5 22.5 20.3
0.5
Theoretical Amt. Insol.,
0.4
1.8
0.8
+ were aqueous extracts;
a Samples marked were alcoholic extracts
2.86
0.62 1.66 3.4 3.22 2.3 1.0 remainder
Vol. XLI, NO.9
traction of the strychnine (after making alkaline) with fresh chloroform. After removal of the solvent, the alkaloid is finally dissolved in alcohol and estimated titrimetrically. Determination of Hydrastine in Hydrastis Extracts Two grams of sample, dissolved in 10 ml. of 70% alcohol, was transferred to a 100-ml. graduated flask;. 20 rnl. of potassium iodide solution was added, the mixture adjusted to 100 ml. with water, and the flask shaken for several minutes. A portion of 50 ml. of the mixture was filtered off, made alkaline with ammonia, and extracted by shaking with three separate 30-1111. portions of ether. The mixed ethereal extracts were filtered into a tared h s k , the ether was removed by distillation, and the residue was dried to constant weight a t 80". The iinal weight represents the hydrastine from 1 Gm. of sample. Determination of Glycyrrhizin i n Licorice Extracts Two grams was dissolved in a few milliliters of water, and the solution was treated with twice its volume of 95% alcohol to precipitate unwanted gummy matter. The liquid was clarified by centrifuging, and the precipitate was washed with a few milliliters of 70% alcohol; the washings were then centrifuged and added to the main liquid. The mixture was vacuum-distilled to dryness, and the residue was dissolved in a few milliliters of water. The aqueous solution was transferred to a centrifuge tube, twice the volume of dilute sulfuric acid was added, and the mixture was centrifuged. The liquid was poured off from the glycyrrhizin precipitate which was then dissolved in dilute ammonia; the ammonia1 solution was filtered into a tared dish, evaporated to dryness, and the residue was dried to constant weight at 100" Results of Assays The results obtained from the above assays are summarized in Table 11. It will be observed that the percentage of active constituent lost during drying, calculated in terms of the dried extract, was in no instance greater than 5% (i. e., 5% of that present in the original material); this amply supports the evidence obtained in the earlier experiments that, under the specified conditions, the drying of extracts by means of infrared radiation results in the majority of cases in only a small degree of deterioration, as shown by "insoluble matter" determinations. I t should, perhaps, be emphasized that no attempt was made during this investigation to stcp up the infrared drying of extracts to the large scale or to solve any of the chemical engineering problems which would inevitably arise. The author has only a few data relating to the effect of vacuum-oven drying on the insoluble-
TABLE 11 Extract
Active Constituent
Before Drying, %
After Drying. %
Theoretical Value, %
Kola Nux vomica Hydrastis Licorice
Caffeine Strychnine Hydrastine Glycyrrhizin
6.8 6.2 7.8 26.5
8.53 7.63 9.26 30.4
8.7 7.75 9.75 31.3
Recovery,
%
98 98.5 95 97
September, 1952
SCIENTIFIC EDITION
479
TABLE IIr
o
Moisture, Extract
%
Initial Insol., %
Final Insol., %
Theoretical Value, %a
Cascara Aqueous Cascara Aqueous Krameria Aqueous Valerian Aqueous C.nlerian Aqueous
20 24 30 28 21
2.5 2.2 3.4 4.7 1.8
9.2 8.1 15.7 14.3 11.6
3.1 2.9 4.8 6.3 2.8
A w ~ m i n gno inrrease during drying
matter content of the product. The srnall amourtt of information which is available is suiiininrized in Table 111. SUMMARY
The infrared drying of pharmaceutical extracts has been investigated on the laboratory scale. More than forty different samples were dried by this means, and the proportion of insoluble matter was determined in the undried and dried material in each case. By comparing the figures thus obtained before and after drying, it is shown that in the ma-
jority of cases the deterioration which occurs duririfi the drying process is slight. This conclusion is further supported by the results o f some additional experiments, carried out on four of the samples, in which the undried and dried extracts were each assayed for a particular active constituent. None of the samplcs examined required more than fifty minutes' exposure to the infrared radiation; complete drying was invariably effected within that period. The maximum teniperature reached by the material being dried was 80".
A Method for the Differentiation of Hydroxocobalamin from Cyanocobalamin Employing the Ascorbic Acid Reaction* By J. A. CAMPBELL, J. M. McLAUGHLAN, and D. G. CHAPMANt,f The fact that hydroxocobalamin is readily destroyed in solutions containing ascorbic acid while cyanocobalarnin is relatively stable in such solutions has been used as the basis of a procedure to determine hydroxocobalamin in the presence of cyanocobalarnin. The method is simple, and appears to be specific and reliable. OLLOWING earlier work (1, 2) on the reaction Fof vitamin BIP and ascorbic acid, Trenner, et al. (3), reported in 1950 that vitamin Biza (hydroxocobalamin) was readily destroyed in
* Received June 3, 1952, from the Food and Drug Divi sions, Department of National Health and Welfare, Ottawa, Canada. t The authors are indebted to Dr. H H. Fricke, Abbott Laboratories, Chicago, and to Dr. G. E. Boxer. Merck & C o . , Rahway, N . J., for generous supplies of vitamin BLL and Btna respectively. After this work was completc=d. the authors were privileged, through the kindness of Dr. D. V. Frost, Abbott Laboratories. to see the draft of a paper outlining experience in their laboratory with this reaction. The data reported here confirm some of their work.
solutions containing ascorbic acid, and that vitamin B12 (cyanocobalamin) was relatively stable under such conditions. The reaction appeared to be influenced by PH. These data suggested a possible means of differentiating between hydroxocobalamin and cpanocobalamin, using .a microbiological assay as the basis for the test. In 1950, Frost, et ui. (4),reported experience with such a procedure where measurements were made of vitamin By. potency before and after destruction of the vitamin BIZb(hydroxocobalamin) with sodium ascorbate. They also described other factors affecting the reaction, but no details of the method were published. Independent work in this laboratory has led to the development of a somewhat similar method for the differential estimation of vitamins BI2, and B12a in the presence of vitamin Bit. Vita-