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A Comparison of the Pharmacological Properties of Two Nitrated Cyclohexanols*
368
JOURNAL OF THE AMERICAN PHARMACEUTICAL ASSOCIATION
tion of Valamin with respect to eight other drugs are presented in Table I. The RI values presented in the table do not imply that the various substances, including Valamin, listed herein can be identified by these values alone, inasmuch as the Rfdifferences are so small between certain compounds. Fortunately bromisovalum and Valamin each reacted t o ammoniacal silver nitrate with distinct colors (see Table I). Identification of drugs by the color of their spots on a chromatogram proved to be another useful criterion. The color development of Valamin with concentrated sulfuric acid is extremely sensitive but not specific, however the results obtained from the chromatography procedure were of aid in the elimination
Vol. XLVII, No. 5
of the possible presence of the few compounds which
produce colors similar to Valamin in sulfuric acid. REFERENCES
. E., Anderson, R . C., and Gibson, W. R.. ,40(1956). H.. Schumann, H. J., and Junkman, K., iO(1953). l i o n ( J a p a n ) , 8, 26 (IYbb).
(4) Gonzales, T. A,, Vance, M.. Helpern, M.. and Umberger. G. J., “Legal Medicine Pathology and Toxicology,” “Appleton-Century-Crofts, Inc., New York, N. Y.. lY54, p. 1191-1255. (5) Perlman, P. L., and Johnson, C., THISJOURNAL, 41, 13(1852). (6) Schmall, M., Wollisch, E. G . , and Shafer, E. G. G . , Anal. Chem., 29, 1373(195(i).
A Comparison of the Pharmacological Properties of Two Nitrated Cyclohexanols* By WILLIAM J. FLEMING,? EDWARD J. ROWE, and DONALD B. MEYERS The nitrate esters of two isomeric cyclohexanols, meso-inositol and scyllitol, were prepared and their pharmacological effects studied. The compounds exhibited the typical organic polynitrate action of depressing smooth muscle when tested on various isolated tissues such as the rabbit intestine, guinea pig ileum, and rat and rabbit lungs. A typical vasodepressor action was obtained from anesthetized cats and rabbits. The acute toxicity of the nitrates was also determined. The results of this study showed the meso-inositol nitrate to be the more active of the two compounds in depressing smooth muscle of the organs studied. No species variation was noted.
arrangement of the nitrate groups on a series of as a medicament nearly one hundred years isomeric hexahydric alcohols did not appear to ago, various organic polynitrates have been influence the activity of the compounds (8). utilized as smooth muscle relaxants; however, ‘ I n this study, a comparison of the relative relatively little is known regarding their mecha- potency of two isomeric nitrated cyclohexanols nism of action. Since the compounds exhibit was undertaken. activity similar to the metallic and organic EXPERIMENTAL nitrites, it was postulated by Hay (1) and substmtiated by others (2, 3) that the organic Preparation of the Nitrated Products of mesonitrates were converted to nitrite ion in the blood Inositol and Scyllito1.-The spatial configurations and exerted their physiological actions by this of the two isomers of inositol which were used in this study are given below (9). mechanism. More recently, RrantL and co-workers, in a OH OH series of papers (4-7), offer evidence that the organic polynitrates act as intact molecules and not through hydrolysis and reduction to nitrite. This assumption is also held by Marshall (8). I Thus far, little has been done in correlating the OH spatial configuration necessary to obtain maximeso-Inositol mum depressor activity of the organic nitrates. OH It is known that methyl nitrate has little deI pressor properties while most of the active members of the series are derived from polyalcohols. However, Marshall found that the INCE THE INTRODUCTION of glyceryl trinitrate
S
7””
*
Received April 16, 19.56, from Butler University College of Pharmacy, Indianapolis, Ind. t Fellow, American Foundation for Pharmaceutical Education, 19541955.
I
HO
Scyllitol
May 1958
SCIENTIFIC EDITION
369
Inositol Nitrate.-meso-Inositol nitrate was pre- throughout the study. The free ends of the segpared by dissolving 5 Gm. (0.028 moles) of anhy- ments were attached t o lever-arms for kymograph drous meso-inositol in 10 ml. (0.22 moles) of cold, recording. fuming nitric acid. After complete solution was obThe results of this experiment showed that mesotained, 10 ml. of fuming sulfuric acid was slowly inosotol nitrate, in doses of 0 . 5 1 . 0 mg., was active added with constant stirring. During this time a in lowering both the tone and amplitude of intestinal white, magma-like mass formed. The temperature muscle while comparable concentrations of scyllitol nitrate exhibited little activity. maintained throughout the synthesis was 0-5'. The precipitate was diluted with cold distilled water, The vehicle, propylene glycol, caused a n immedifiltered, washed thoroughly with cold water, and ate slight fall in tone which was followed by an increase in tone and a decrease in amplitude when addried under a carbon dioxide atmosphere. The product, when recrystallized two times from ministered in doses of 3 ml. a 2 : l v/v mixture of 95% ethanol and water and Antagonism Against Histamine Induced Spasm two times from benzene, melted a t 119-12Io1 which of Isolated Guinea Pig Ileum.-Ileal segments of is in agreement with that recorded for the hexani- nonfasting guinea pigs were isolated and suspended trate. A yield of 31.6y0 was obtained. in a water bath containing aerated Locke-Ringer's meso-Inositol nitrate is a fine, white, crystalline solution at a temperature of 37-38'. The bath powder which decomposes readily in the dry form volume was 100 ml. throughout the experiment. when exposed to the atmosphere a t room tempera- The system was organized for kymograph recording ture. It is insoluble in water but is soluble in alco- in the usual manner. hol, propylene glycol, acetic anhydride, and warm After tracings of normal ileal movements were obbenzene. tained, 0.1 ml. of histamine acid phosphate, 1:1000, And-Calcd. for CSHSN&: N, 18.67. Found: was added to the preparation to produce a n immediN, 17.48 (Kjeldahl). ate ileal spasm. The drug was left in contact with Scyllitol Nitrate.-The nitrated product of scylli- the tissue for two and one-half minutes. The segto1 was prepared by adding, with stirring, 4 Gm. ment was then washed and the contractions allowed (0.022 moles) of scyllitol to 10 ml. (0.22 moles) of t o return to normal. The same procedure was folfuming nitric acid. Upon standing, a white, lowed in subsequent trials, with the alteration that magma-like mass formed which did not dissolve in thirty seconds after the dose of histamine acid the acid. Fuming sulfuric acid, 10 ml.. was slowly phosphate, meso-inositol nitrate or scyllitol nitrate added with constant stirring. The temperature was added in varying concentrations. Their efwas maintained at 0-5' throughout the procedure. fects of alleviating the spastic ileum were noted over The precipitate was diluted with ice water, filtered, a time interval of two minutes. washed thoroughly with cold water, and dried under It was determined by this study that mesoa carbon dioxide atmosphere. inositol nitrate was 1.46 times as active as scyllitol The final product is a dense, white powder which nitrate in doses of 1.5 mg., and 1.99 times as active melted a t 123-125" with decomposition. A yield in doses of 1.0 mg.,in relaxing the spastic ileum after of 90.75% was obtained. It is insoluble in water the addition of histamine. and the common organic solvents. Guinea Pig Tracheal Chain.-The tracheae of And-Calcd. for CE.HE.NSOI~: c , 16.01; H, 1.33; two albino, female guinea pigs were used t o prepare N, 18.66. Found: C, 18.05; H, 1.57; N, 15.84 a chain according t o the method of Castillo and (Kjeldahl). DeBeer (10). The chain was suspended in aerated Van Dyke-Hastings solution modified by the addiPHARMACOLOGY tion of 0.05% dextrose. The bath was maintained a t a temperature of 37-38' and a volume of 100 ml. Since the organic polynitrates exhibit relaxing throughout the experiment. actions on many organs containing smooth muscle, Histamine acid phosphate, 0.5 mg., was added to a pharmacological comparison of the two compounds the bath to cause a contraction of the chain. Neither was made by studying their relative effects on the of the compounds under study, in doses up t o 3 mg., vascular system, small intestine, uterine muscle, produced any antagonism to histamine induced trachial chain, and isolated lung. tracheal spasm when administered before or after In all studies except that of acute toxicity, the the histamine. compounds were administered in a propylene glycol Isolated Guinea Pig Uterus.-Uterine segments of vehicle. meso-Inositol nitrate was soluble in a connongravid guinea pigs were obtained and suspended centration of 10 mg./ml., while the scyllitol nitrate in aerated Locke-Ringer's solution a t a temperature formed a uniform suspension. Acute toxicity stud- of 27-38". The bath volume was 100 ml. ies of both drugs were carried out with the comDoses as high as 3 mg. of either meso-inositol pounds suspended in a 0.i5yonietliylcellulose solunitrate or scyllitol nitrate had no activity in relaxing tion. the tissue or antagonizing contractions caused by posterior pituitary, U. S. P., in concentrations of PERFUSION STUDIES 1 x 10-3 units/ml. Isolated Lung Perfusion.-The lungs and trachea Isolated Rabbit Intestine.-Randomly selected segments of small intestine from non-fasting, albino were removed from a rabbit or rat and placed on a rabbits were isolated and suspended in water baths T-type cannula. Modified Locke-Ringer's solution containing aeratedTyrode's solution a t a temperature was then perfused through the lung at a positive. The volume of the bath was 100 ml. constant pressure and a temperature of 37-38'. of 37-38'. Aftc- expressing the residual air in the lungs through the sidearm of the cannula, the drugs were injected 1 The melting points were determined with a Fisher-Johns into the perfusion fluid a t a rate of 1 ml./min. and apparatus.
JOURNAL OF THE A ~ R I C APKARMACBUTICAL N ASSOCIATION
370
their actions in altering the rate of outflow were noted. It was found that meso-inositol nitrate in doses of 5 mg. and 10 mg. was active in increasing the lung outflow in the rat, but the results were not conclusive in the rabbit study. Scyllitol nitrate was somewhat active in increasing outflow in both the rat and rabbit; however, the compound was not as potent as its meso-inositol isomer in duration of action or outflow when compared in equal doses on the isolated r a t lung.
Vol. XLVII, No. 5
cellulose solution. The test animals were placed in cages by dose and observed over a period of 72 hours. The majority of mortalities occurred after 24 hours and before 48 hours. The only apparent toxic sign was a cyanosis seen in the tail four hours after injection. The LDSOand standard error of the compounds was calculated by the method of Bliss (11). The LDKO of meso-inositol nitrate was found to be 0.957 f 0.057 Gm./Kg. The LD6o of scyllitol nitrate was computed to be 1.267 f 0.088 Gm./Kg.
BLOOD PRESSURE STUDIES DISCUSSION Anesthetized Rabbit.-Six albino rabbits of either sex and weighing 3 . H . 1 Kg. were anesthetized with urethane, 1.5 Gm./Kg., rectally and maintained throughout the experiment with intravenous injections of secobarbital sodium as needed. The animals were prepared for blood pressure and respiration recording by cannulating the right common carotid artery and trachea. All injections were introduced through the marginal ear vein. Both of the drugs were effective in lowering blood pressure in doses of 5 mg. (Table I). The fall in blood pressure took place within ten seconds after the injection had begun and was accompanied by a n increase in the rate and amplitude of respiration. Doses lower than 5 mg. produced rather transient depressions in pressure. The same general responses were obtained after double vagotomy. Anesthetized Cat.-Three female cats weighing 2.1-2.9 Kg. were anesthetized with phenobarbital sodium, 175 mg./Kg., by intraperitoneal injection. The animals were prepared for blood pressure and respiratory studies in the usual manner. All injections were introduced through the left external jugular vein. The results of this study are essentially the same as observed in the rabbit and are tabulated in Table I. It can be seen that meso-inositol nitrate is the more active of the two compounds from the standpoint of the amount of fall in pressure and duration of action.
TABLE I.-BLOOD PRESSURE STUDY IN THE CATAND RABBIT
Dose, Drug
m-Inositol Nitrate Scyllitol Nitrate m-Inositol Nitrate Scyllitol Nitrate m-Inositol Nitrate Scyllitol Nitrate a
mg.
Av.” Fall in Systolic B.P., mm. Rabhit Cat
Av.0 Duration of Action, min. Rabbit Cat
.. ..
5
23
..
8.8
5
19
..
5.3
10
32
33
9.6
11
10
21
21
6.G
9
15
30
31
5.1
9.5
15
19
22
6.2
7.5
Av. in 6 rabbits and 3 cats.
Acute Toxicity-Intraperitoneal LDa.-Albino mice, weighting 14-20 Grn., were injected intraperitoneally with the drugs suspended in a 0.5% methyl
The data obtained from the pharmacological comparison of the nitrated products of meso-inositol and scyllitol indicates that meso-inositol nitrate is the more active of the two compounds in relaxing the smooth muscle of the various organs studied from the standpoint of the amount of activity and duration of action. In comparing the relative potency of the two drugs, several factors should be considered: spatial relationships, solubility, and the degree of nitration obtained. It can be seen from the structural configurations that meso-inositol has three adjoining hydroxyl groups on the same side of the plane of the cyclohexane ring, while the hydroxyl groups of scyllitol alternate above and below the plane of the ring; and therefore, none of the groups are directly adjacent. As yet, the relationships necessary for the organic polynitrates t o exhibit maximum depressor activity is not known, but since methyl nitrate and ethylene glycol dinitrate have little smooth muscle relaxant properties while activity increases with higher members of the series, i t may be possible t o draw some correlation of activity with the number of adjacent nitrate groups on the molecule. Secondly, from the previously described physical properties of the two compounds, it is evident that scyllitol nitrate is generally the more insoluble. This factor could well play a part in limiting the activity of the drug by altering its contact and fixing abilities with the smooth muscle tissue. Although analytical determinations indicate that meso-inositol nitrate was more completely nitrated than the scyllitol derivative, the importance of this factor is not known; however, in most cases the pharmacological response produced by meso-inositol nitrate could not be obtained with even twice the quantity of scyllitol nitrate.
REFERENCES (1) Hay M . Trans. Roy. SOC.Edinburgh 32, 67(1883). (2) Lee& D’. J., Brit. Med. J . , 1. 1305(18b3). (3) Herrman, R. F . , I.eake, C. D., Loevenhart, A. S.. and Muehlberger, C. W., J . Pkarmacol. E x p f l . Therap., 27, 259 (1926). (4) Krantz, J. C., Jr., Carr, C. J., Forman, S., and Ellis, F.W., ibid., 67, 187(1939). (5) Ibid., 67, 191(1939). (6) Krantz, J. C., Jr.. Carr, C. I.,Furman, S., and Cone, N . , ibid., 70,323(1940). (7) Rath, M.M., and Krantz, J. C., Jr., ibid., 76, 33 (1842).
(8) Marshall, C. R., ibid. 83 106(1945). (9) Pigman. W. W., and’WAflrom, M . L., “Advances in Carbohydrate Chemistry,” Vol.3,Academic Press Inc., New York, 1948, p. 47. (10) Castillo, J. C., and DeBeer, E. J., J . Pharmacol. Exfifl. Therap.. 90, 104(1947) (11) Bliss, C.I., Quart. J . Pharm. a7nd Pkarmacol., 11, 192 (1938).
JOURNAL OF THE AMERICAN PHARMACEUTICAL ASSOCIATION
tion of Valamin with respect to eight other drugs are presented in Table I. The RI values presented in the table do not imply that the various substances, including Valamin, listed herein can be identified by these values alone, inasmuch as the Rfdifferences are so small between certain compounds. Fortunately bromisovalum and Valamin each reacted t o ammoniacal silver nitrate with distinct colors (see Table I). Identification of drugs by the color of their spots on a chromatogram proved to be another useful criterion. The color development of Valamin with concentrated sulfuric acid is extremely sensitive but not specific, however the results obtained from the chromatography procedure were of aid in the elimination
Vol. XLVII, No. 5
of the possible presence of the few compounds which
produce colors similar to Valamin in sulfuric acid. REFERENCES
. E., Anderson, R . C., and Gibson, W. R.. ,40(1956). H.. Schumann, H. J., and Junkman, K., iO(1953). l i o n ( J a p a n ) , 8, 26 (IYbb).
(4) Gonzales, T. A,, Vance, M.. Helpern, M.. and Umberger. G. J., “Legal Medicine Pathology and Toxicology,” “Appleton-Century-Crofts, Inc., New York, N. Y.. lY54, p. 1191-1255. (5) Perlman, P. L., and Johnson, C., THISJOURNAL, 41, 13(1852). (6) Schmall, M., Wollisch, E. G . , and Shafer, E. G. G . , Anal. Chem., 29, 1373(195(i).
A Comparison of the Pharmacological Properties of Two Nitrated Cyclohexanols* By WILLIAM J. FLEMING,? EDWARD J. ROWE, and DONALD B. MEYERS The nitrate esters of two isomeric cyclohexanols, meso-inositol and scyllitol, were prepared and their pharmacological effects studied. The compounds exhibited the typical organic polynitrate action of depressing smooth muscle when tested on various isolated tissues such as the rabbit intestine, guinea pig ileum, and rat and rabbit lungs. A typical vasodepressor action was obtained from anesthetized cats and rabbits. The acute toxicity of the nitrates was also determined. The results of this study showed the meso-inositol nitrate to be the more active of the two compounds in depressing smooth muscle of the organs studied. No species variation was noted.
arrangement of the nitrate groups on a series of as a medicament nearly one hundred years isomeric hexahydric alcohols did not appear to ago, various organic polynitrates have been influence the activity of the compounds (8). utilized as smooth muscle relaxants; however, ‘ I n this study, a comparison of the relative relatively little is known regarding their mecha- potency of two isomeric nitrated cyclohexanols nism of action. Since the compounds exhibit was undertaken. activity similar to the metallic and organic EXPERIMENTAL nitrites, it was postulated by Hay (1) and substmtiated by others (2, 3) that the organic Preparation of the Nitrated Products of mesonitrates were converted to nitrite ion in the blood Inositol and Scyllito1.-The spatial configurations and exerted their physiological actions by this of the two isomers of inositol which were used in this study are given below (9). mechanism. More recently, RrantL and co-workers, in a OH OH series of papers (4-7), offer evidence that the organic polynitrates act as intact molecules and not through hydrolysis and reduction to nitrite. This assumption is also held by Marshall (8). I Thus far, little has been done in correlating the OH spatial configuration necessary to obtain maximeso-Inositol mum depressor activity of the organic nitrates. OH It is known that methyl nitrate has little deI pressor properties while most of the active members of the series are derived from polyalcohols. However, Marshall found that the INCE THE INTRODUCTION of glyceryl trinitrate
S
7””
*
Received April 16, 19.56, from Butler University College of Pharmacy, Indianapolis, Ind. t Fellow, American Foundation for Pharmaceutical Education, 19541955.
I
HO
Scyllitol
May 1958
SCIENTIFIC EDITION
369
Inositol Nitrate.-meso-Inositol nitrate was pre- throughout the study. The free ends of the segpared by dissolving 5 Gm. (0.028 moles) of anhy- ments were attached t o lever-arms for kymograph drous meso-inositol in 10 ml. (0.22 moles) of cold, recording. fuming nitric acid. After complete solution was obThe results of this experiment showed that mesotained, 10 ml. of fuming sulfuric acid was slowly inosotol nitrate, in doses of 0 . 5 1 . 0 mg., was active added with constant stirring. During this time a in lowering both the tone and amplitude of intestinal white, magma-like mass formed. The temperature muscle while comparable concentrations of scyllitol nitrate exhibited little activity. maintained throughout the synthesis was 0-5'. The precipitate was diluted with cold distilled water, The vehicle, propylene glycol, caused a n immedifiltered, washed thoroughly with cold water, and ate slight fall in tone which was followed by an increase in tone and a decrease in amplitude when addried under a carbon dioxide atmosphere. The product, when recrystallized two times from ministered in doses of 3 ml. a 2 : l v/v mixture of 95% ethanol and water and Antagonism Against Histamine Induced Spasm two times from benzene, melted a t 119-12Io1 which of Isolated Guinea Pig Ileum.-Ileal segments of is in agreement with that recorded for the hexani- nonfasting guinea pigs were isolated and suspended trate. A yield of 31.6y0 was obtained. in a water bath containing aerated Locke-Ringer's meso-Inositol nitrate is a fine, white, crystalline solution at a temperature of 37-38'. The bath powder which decomposes readily in the dry form volume was 100 ml. throughout the experiment. when exposed to the atmosphere a t room tempera- The system was organized for kymograph recording ture. It is insoluble in water but is soluble in alco- in the usual manner. hol, propylene glycol, acetic anhydride, and warm After tracings of normal ileal movements were obbenzene. tained, 0.1 ml. of histamine acid phosphate, 1:1000, And-Calcd. for CSHSN&: N, 18.67. Found: was added to the preparation to produce a n immediN, 17.48 (Kjeldahl). ate ileal spasm. The drug was left in contact with Scyllitol Nitrate.-The nitrated product of scylli- the tissue for two and one-half minutes. The segto1 was prepared by adding, with stirring, 4 Gm. ment was then washed and the contractions allowed (0.022 moles) of scyllitol to 10 ml. (0.22 moles) of t o return to normal. The same procedure was folfuming nitric acid. Upon standing, a white, lowed in subsequent trials, with the alteration that magma-like mass formed which did not dissolve in thirty seconds after the dose of histamine acid the acid. Fuming sulfuric acid, 10 ml.. was slowly phosphate, meso-inositol nitrate or scyllitol nitrate added with constant stirring. The temperature was added in varying concentrations. Their efwas maintained at 0-5' throughout the procedure. fects of alleviating the spastic ileum were noted over The precipitate was diluted with ice water, filtered, a time interval of two minutes. washed thoroughly with cold water, and dried under It was determined by this study that mesoa carbon dioxide atmosphere. inositol nitrate was 1.46 times as active as scyllitol The final product is a dense, white powder which nitrate in doses of 1.5 mg., and 1.99 times as active melted a t 123-125" with decomposition. A yield in doses of 1.0 mg.,in relaxing the spastic ileum after of 90.75% was obtained. It is insoluble in water the addition of histamine. and the common organic solvents. Guinea Pig Tracheal Chain.-The tracheae of And-Calcd. for CE.HE.NSOI~: c , 16.01; H, 1.33; two albino, female guinea pigs were used t o prepare N, 18.66. Found: C, 18.05; H, 1.57; N, 15.84 a chain according t o the method of Castillo and (Kjeldahl). DeBeer (10). The chain was suspended in aerated Van Dyke-Hastings solution modified by the addiPHARMACOLOGY tion of 0.05% dextrose. The bath was maintained a t a temperature of 37-38' and a volume of 100 ml. Since the organic polynitrates exhibit relaxing throughout the experiment. actions on many organs containing smooth muscle, Histamine acid phosphate, 0.5 mg., was added to a pharmacological comparison of the two compounds the bath to cause a contraction of the chain. Neither was made by studying their relative effects on the of the compounds under study, in doses up t o 3 mg., vascular system, small intestine, uterine muscle, produced any antagonism to histamine induced trachial chain, and isolated lung. tracheal spasm when administered before or after In all studies except that of acute toxicity, the the histamine. compounds were administered in a propylene glycol Isolated Guinea Pig Uterus.-Uterine segments of vehicle. meso-Inositol nitrate was soluble in a connongravid guinea pigs were obtained and suspended centration of 10 mg./ml., while the scyllitol nitrate in aerated Locke-Ringer's solution a t a temperature formed a uniform suspension. Acute toxicity stud- of 27-38". The bath volume was 100 ml. ies of both drugs were carried out with the comDoses as high as 3 mg. of either meso-inositol pounds suspended in a 0.i5yonietliylcellulose solunitrate or scyllitol nitrate had no activity in relaxing tion. the tissue or antagonizing contractions caused by posterior pituitary, U. S. P., in concentrations of PERFUSION STUDIES 1 x 10-3 units/ml. Isolated Lung Perfusion.-The lungs and trachea Isolated Rabbit Intestine.-Randomly selected segments of small intestine from non-fasting, albino were removed from a rabbit or rat and placed on a rabbits were isolated and suspended in water baths T-type cannula. Modified Locke-Ringer's solution containing aeratedTyrode's solution a t a temperature was then perfused through the lung at a positive. The volume of the bath was 100 ml. constant pressure and a temperature of 37-38'. of 37-38'. Aftc- expressing the residual air in the lungs through the sidearm of the cannula, the drugs were injected 1 The melting points were determined with a Fisher-Johns into the perfusion fluid a t a rate of 1 ml./min. and apparatus.
JOURNAL OF THE A ~ R I C APKARMACBUTICAL N ASSOCIATION
370
their actions in altering the rate of outflow were noted. It was found that meso-inositol nitrate in doses of 5 mg. and 10 mg. was active in increasing the lung outflow in the rat, but the results were not conclusive in the rabbit study. Scyllitol nitrate was somewhat active in increasing outflow in both the rat and rabbit; however, the compound was not as potent as its meso-inositol isomer in duration of action or outflow when compared in equal doses on the isolated r a t lung.
Vol. XLVII, No. 5
cellulose solution. The test animals were placed in cages by dose and observed over a period of 72 hours. The majority of mortalities occurred after 24 hours and before 48 hours. The only apparent toxic sign was a cyanosis seen in the tail four hours after injection. The LDSOand standard error of the compounds was calculated by the method of Bliss (11). The LDKO of meso-inositol nitrate was found to be 0.957 f 0.057 Gm./Kg. The LD6o of scyllitol nitrate was computed to be 1.267 f 0.088 Gm./Kg.
BLOOD PRESSURE STUDIES DISCUSSION Anesthetized Rabbit.-Six albino rabbits of either sex and weighing 3 . H . 1 Kg. were anesthetized with urethane, 1.5 Gm./Kg., rectally and maintained throughout the experiment with intravenous injections of secobarbital sodium as needed. The animals were prepared for blood pressure and respiration recording by cannulating the right common carotid artery and trachea. All injections were introduced through the marginal ear vein. Both of the drugs were effective in lowering blood pressure in doses of 5 mg. (Table I). The fall in blood pressure took place within ten seconds after the injection had begun and was accompanied by a n increase in the rate and amplitude of respiration. Doses lower than 5 mg. produced rather transient depressions in pressure. The same general responses were obtained after double vagotomy. Anesthetized Cat.-Three female cats weighing 2.1-2.9 Kg. were anesthetized with phenobarbital sodium, 175 mg./Kg., by intraperitoneal injection. The animals were prepared for blood pressure and respiratory studies in the usual manner. All injections were introduced through the left external jugular vein. The results of this study are essentially the same as observed in the rabbit and are tabulated in Table I. It can be seen that meso-inositol nitrate is the more active of the two compounds from the standpoint of the amount of fall in pressure and duration of action.
TABLE I.-BLOOD PRESSURE STUDY IN THE CATAND RABBIT
Dose, Drug
m-Inositol Nitrate Scyllitol Nitrate m-Inositol Nitrate Scyllitol Nitrate m-Inositol Nitrate Scyllitol Nitrate a
mg.
Av.” Fall in Systolic B.P., mm. Rabhit Cat
Av.0 Duration of Action, min. Rabbit Cat
.. ..
5
23
..
8.8
5
19
..
5.3
10
32
33
9.6
11
10
21
21
6.G
9
15
30
31
5.1
9.5
15
19
22
6.2
7.5
Av. in 6 rabbits and 3 cats.
Acute Toxicity-Intraperitoneal LDa.-Albino mice, weighting 14-20 Grn., were injected intraperitoneally with the drugs suspended in a 0.5% methyl
The data obtained from the pharmacological comparison of the nitrated products of meso-inositol and scyllitol indicates that meso-inositol nitrate is the more active of the two compounds in relaxing the smooth muscle of the various organs studied from the standpoint of the amount of activity and duration of action. In comparing the relative potency of the two drugs, several factors should be considered: spatial relationships, solubility, and the degree of nitration obtained. It can be seen from the structural configurations that meso-inositol has three adjoining hydroxyl groups on the same side of the plane of the cyclohexane ring, while the hydroxyl groups of scyllitol alternate above and below the plane of the ring; and therefore, none of the groups are directly adjacent. As yet, the relationships necessary for the organic polynitrates t o exhibit maximum depressor activity is not known, but since methyl nitrate and ethylene glycol dinitrate have little smooth muscle relaxant properties while activity increases with higher members of the series, i t may be possible t o draw some correlation of activity with the number of adjacent nitrate groups on the molecule. Secondly, from the previously described physical properties of the two compounds, it is evident that scyllitol nitrate is generally the more insoluble. This factor could well play a part in limiting the activity of the drug by altering its contact and fixing abilities with the smooth muscle tissue. Although analytical determinations indicate that meso-inositol nitrate was more completely nitrated than the scyllitol derivative, the importance of this factor is not known; however, in most cases the pharmacological response produced by meso-inositol nitrate could not be obtained with even twice the quantity of scyllitol nitrate.
REFERENCES (1) Hay M . Trans. Roy. SOC.Edinburgh 32, 67(1883). (2) Lee& D’. J., Brit. Med. J . , 1. 1305(18b3). (3) Herrman, R. F . , I.eake, C. D., Loevenhart, A. S.. and Muehlberger, C. W., J . Pkarmacol. E x p f l . Therap., 27, 259 (1926). (4) Krantz, J. C., Jr., Carr, C. J., Forman, S., and Ellis, F.W., ibid., 67, 187(1939). (5) Ibid., 67, 191(1939). (6) Krantz, J. C., Jr.. Carr, C. I.,Furman, S., and Cone, N . , ibid., 70,323(1940). (7) Rath, M.M., and Krantz, J. C., Jr., ibid., 76, 33 (1842).
(8) Marshall, C. R., ibid. 83 106(1945). (9) Pigman. W. W., and’WAflrom, M . L., “Advances in Carbohydrate Chemistry,” Vol.3,Academic Press Inc., New York, 1948, p. 47. (10) Castillo, J. C., and DeBeer, E. J., J . Pharmacol. Exfifl. Therap.. 90, 104(1947) (11) Bliss, C.I., Quart. J . Pharm. a7nd Pkarmacol., 11, 192 (1938).