Expectorants comprising N-acetylneuraminic acid and its salts

Abstract: An expectorant capable of acting on the rheological properties of sputum and capable of directly promoting the ciliary motion. The expectorant contains N-acetylneuramin­ ic acid or a pharmaceutically active salt thereof.

Description: The present invention relates to an expectorant. More particularly, the invention is concerned with an expectorant made of the pharmaceutically active salts of N-acetylneuraminic acid having an effect of directly promoting ciliary motion while acting on the rheological property of sputum. Viscous secretion exists in the airway of the human body. The secretion has an important role in imparting suitable temperature and humidity to inhaled air. The matter generally referred to as "sputum" is constituted mainly by this secretion. When its amount is moderate, the secretion in the airway is unconsciously swallowed or expelled with the breath, but usually is never expectorated. Thus, any expectoration suggests that there is something extraordinary in the respiratory system. On the other hand, accumulation of sputum to be expectorated in the airway is liable to cause an infection via the airway. From this point of view, the removal of sputum is a matter of great significance in the medical treatment of patients who suffer from a disease in the airway. Sputum is often very viscous and sticky so that expectoration causes the patient pain. P. Görög and Iren B. Kovács describe in "Agents and Actions", Vol. 8, no.5 (1978), page 543 the pharmaceutical properties of sialic acid like anti-inflammatory properties. R. Shauer describes in "Sialic acids, chemistry, metabolism, and function " on page 289 (1984) that mucins form a continuous lining on the inside surface of the bronchial system and, by virtue of their viscous and elastic properties, they are involved in transport and secretion processes. Lopez - Vidríero et. al. describe in "Thorax" (1973), Vol.28, page 401 that the viscosity and pourability of mucoid sputum is correlated with it's N-acetylneuraminic acid content. In order to facilitate expectoration a medicine which is referred to as "expectorant" has been used. This medicine is given in a general dosage orally or by injection. The expectorant thus administered serves to remove sputum by diluting the sputum through an increase in secretion by the mucosa of the airway, promotion of separation from the mucosa and enhancement of ciliary beat. This , however, involves various clinical problems concerning mechanism and effect. The present inventors have therefore made intensive studies and found that sialic acids may serve as an effective expectorant which can be used locally. This invention has been accomplished through a study on the sputum-removing effect offered by the salts of N-acetylneuraminic acid. Accordingly, an object of the invention is to provide an expectorant mainly composed of the salts of N-acetylneuraminic acid which acts on the rheological property of sputum and which directly promotes ciliary beat so as to facilitate the expectoration. The expectorant of the invention contains, as effective components, salts of N-acetylneuraminic acid of the following general formula: On condition of n = 1, Z represents lithium, potassium, sodium, ammonium, or organic ammonium, whereas, on condition of n = 2, Z represents calcium, barium or magnesium. The N-acetylneuraminic acid itself is a known compound, and its salts can be obtained by neutralizing this acid with a hydroxide or carbonate of an alkali metal or alkali earth metal and separating the corresponding alkali metal salt or alkali earth metal salt from the system. According to the invention, this compound is used in such a form as to permit the use of a known local administration method such as inhalation of the pulverized compound from an aerosol. The effect of the salts as of N-acetylneuraminic acid an expectorant is attributable to the following two functions: namely, physiological change for easier expectoration by acting on the rheological property of the expectorant such as its fluidity, yield value, spinnability, stickiness, stress relaxing time and so forth, and promotion of sputum transportation by cilia through direct activation of ciliary beat of the cilia in the airway. These functions have been confirmed through an experiment in which the rotary motion of a cilium group before the application of the salts of N-acetylneuraminic acid was compared with that after the application, using cilium cells in the human airway, as well as through an experiment in which the sputum conveying property of cilia of frog palatine mucosa in the state after the application of the salts of N-acetylneuraminic acid was compared with that before the application. In clinical use, the expectorant of the invention is used in the form of, for example, the following preparation. As the first step, a salt of N-acetylneuraminic acid is well ground and mashed in an agate mortar to reduce it to a fine powder of a grain size ranging between 1 and 20 microns. Lactose is then gradually mixed with the fine powder and diluted 10 to 20 fold. Then, 20 to 40 mg of the mixture is put in a capsule or envelope by a known method. Preferably, a capsule is used for powdered aerosol, and an envelope is used for liquid aerosol. Whether the expectorant is used as a powdered aerosol or liquid aerosol is determined on the basis of the symptoms of the patient. The dose is usually 0.5 to 5 mg/time. The expectorant should be administered at least two times a day but this may be changed if the symptoms warrant it. The results of pharmacodynamic tests and acute toxicity tests showed that the number of dosage per day need not be limited. The expectorant is administered, when used in the form of a powdered aerosol, by means of a powder spray such as an insufflator or nebulizer, and when used as a liquid aerosol, by a liquid atomizer such as a nebulizer. The effect of the invention can be summarized as follows: the expectorant of the invention exhibits a superior sputum-removing effect when administered locally. Namely, it changes the property of sputum to ease expectoration by acting on the rheological property of sputum, e.g. yield value and viscosity. On the other hand, it directly activates the ciliated cells to promote expectoration by ciliary beat. Description will be now made hereinunder as to the way of synthesis of the compound of the invention, as well as the effect of the same, through preferred examples. Example 1 Method of Synthesizing Ammonium Salt of N-Acetylneuraminic Acid 12 g of N-acetylneuraminic acid was dissolved in 150 ml of water to form an aqueous solution into which was stirred a saturated aqueous solution of ammonium until the solution becomes neutral (pH 6.7). The reaction solution was spontaneously filtrated and the residual was freeze-dried (one day) to form 13.2 g of white crystals. Melting Point: about 150 o C decomposed, Qualitative Reaction of Ammonium Salt: According to General Testing Method of the "Pharmacopeia of Japan", 10th Edition An excess amount of sodium hydroxide reagent was added to the ammonium salt and the mixture was heated. The mixture gave off an odor of ammonium and the fume changed a red litmus paper blue. Example 2: Method of synthesizing Calcium Salt of N-Acetylneuraminic Acid 200 ml of distilled water was added to a mixture of 10.1 g (0.0323 mole) of N-acetylneuraminic acid and 1.162 g (0.0162 mole) of calcium carbonate. The solution was stirred for 2 hours at room temperature until the calcium carbonate was completely dissolved (pH 6.55). The solution was filtered and the deposit was subjected to freeze-drying and decompression drying to form 11.0 g of colorless needle crystals. Melting Point: 140 o or higher (decomposed) Qualitative Test of Calcium Salt According to General Testing Method of Pharmacopeia of Japan 10th Edition (1) A yellowish red was observed in a flame reaction test of the calcium salt. (2) A white precipitate was observed when an ammonium carbonate reagent was added to the calcium salt. 3600 - 3000, 1620 1560 (NMR(D₂O)ppm) 1.59 - 2.42 (m) 2.05(s), 3.71 (s) 3.99(s) Salts of lithium, potassium, sodium, organic ammonium, barium and magnesium of N-acetylneuraminic acid were prepared in the same way as that described above. Namely, the N-acetylneuraminic acid was neutralized with hydroxides or carbonates of these elements, followed by freeze-drying, thus obtaining salts of the N-acetylneuraminic acid. Example 3: Effect of Calcium Salt of N-acetylneuraminic acid on Ciliary Movement of Palatine Mucosa of Frog Bull frogs (furnished by Saitama Test Animal) weighing 300 to 450 g were used regardless of sex. The calcium salt of N-acetylneuraminic acid (provided by Kanto Ishiseiyaku Kabushiki Kaisha), as well as acetylcholine chloride (furnished by Sigma Kabushiki Kaisha) were used as test substances. Mucociliary transport was measured by the particle transport method. After decapitation of a frog, the surface of the palatine mucosa was separated with minimized damage and fixed to a cork plate in a Petri dish which was then filled with 20 ml of Ringer's solution (trishydrochloric acid). The palatine mucosa was left in this state for 30 minutes before the commencement of measurement. For measurement, the Ringer's solution was removed and fine pieces of cork (capable of passing pharmaceutical sieve No. 5 but not capable of passing No. 6) were placed on the surface of the palatine mucosa, and the time (in seconds) required for the cork piece to move 1 cm was measured. The duration of movement, i.e., moving speed, was measured also in the state immediately after the removal of the Ringer's solution or pharmaceutical solution. It was confirmed that the calcium salt of N-acetylneuraminic acid causes an acceleration of the ciliary movement of palatine mucosa in a certain dose-dependency, as will be seen from Table 3. This result was substantially equal to that produced by acetylcholine (control) at concentrations of 10⁻⁵ and 10⁻⁴ g/ml, as will be seen from Table 2. The calcium salt of N-acetylneuraminic acid was confirmed as producing substantially the same ciliary movement promoting effect as the acetylcholine which has been known as being effective in the promotion of ciliary movement. The calcium salt of N-acetylneuraminic acid, therefore, is expected to facilitate expectoration. The acetylcholine, however, cannot be used as an expectorant because it causes undesirable effects such as bronchoconstriction and crinogenic action, although it promotes ciliary action. In contrast, the calcium salt of N-acetylneuraminic acid can be used as an expectorant because it effectively promotes ciliary action, without being accompanied by the detrimental effects produced by acetylcholine. Example 4: Effect of the Calcium Salt on of N-acetylneuraminic Acid Rotation of Ciliated Cell Using ciliated cells from the human airway and frog palate, rotation of cell groups due to ciliary beat was observed before and after application of the calcium salt of N-acetylneuraminic acid, in order to confirm the effect of these agents on the ciliated cells. Human ciliated cells were collected from a normal trachea by means of a branchoscope, the ciliated cells being separated by rubbing the bronchus while observing through the branchoscope, while the collection of frog ciliated cells was conducted by rubbing the palatine mucosa, without being specially careful. The cilium cells thus obtained were floated in Medium 199 (prepared by Gibco Company) and groups of ciliated cells, each consisting of several cells exhibiting rotary motion due to ciliary motion, were sucked up by a microsyringe in such a manner as to avoid damage to such cells, using observation through a phase contrast microscope. The groups of cells were transferred to a cover slip and one drop of chicken plasma (prepared by Difco Company) and one drop of 50% chicken embryo extract were added to the cells, thus forming clots. The rotary motion in the clots was recorded by means of a video recorder and the number of rotations per minute was measured. The agents were dissolved in the Medium 199 and were injected through a tube attached to a rose chamber. The states of rotary motion 5 minutes, 10 minutes and 15 minutes after the injection were recorded by means of a video recorder, and the number of revolutions was measured. With application of N-acetylneuraminic acid (10⁻⁴ to 10⁻¹ mg/ml), the rotary motion of the cilium cells is gradually accelerated starting immediately after the application. 5 minutes, 10 minutes and 15 minutes after the application, plateaus were observed at application rates of 10⁻³ to 10⁻² mg/ml. In these plateaus, the speed in revolutions per minute was about 25% higher than that in the Medium 199, as will be seen from Figs. 1 and 2. It was confirmed also that the rotary motion of the cilium cells is increased by application of 10⁻³ to 3 x 10⁻² mg/ml of terbutaline (5-[2-[(1.1-dimetylethyl) amino]-1-hydoxyethyl]-1,3-benzenediole), in a certain dependency to the dose. The effect was particularly remarkable 5 minutes after the application, as can be seen from Fig. 3. It was confirmed also that the speed of rotary motion of the cilium cells is increased by the addition of 10⁻³ mg/ml and 3 x 10⁻³ mg/ml of acetylcholine. Speed peaks of the rotary motion were observed about 10 minutes and 5 minutes after the application when the amounts of addition were respectively, 10⁻³ mg/ml and 3 x 10⁻³ mg/ml. In both cases, the rotary motion stopped 13 minutes after the application. It was confirmed that terbutalin and acetylcholine, which are known as being effective in promoting ciliary beat, promote also the rotary motion of the cilium cells. N-acetylneuraminic acid was confirmed as also being effective in the promotion of the rotary motion of ciliated cells. It is considered that the rotary motion of the ciliated cells is transmitted into ciliary beat, thereby facilitating the expectoration. This clearly shows that N-acetylneuraminic acid will be effective as an expectorant. Example 5: Synthesis of Sodium Salt of N-Acetylneuraminic acid A small amount of activated carbon was added to an aqueous solution of N-acetylneuraminic acid and, under a flow of nitrogen gas, 1N sodium hydroxide was added to obtain a pH value of pH 7.3 to 7.8. The reacted solution was filtered using a filter of 0.2 µm and the filtrate was freeze-dried, forming a colorless powder of sodium salt of N-acetylneuraminic acid. 1R 3400 cm⁻¹, 2937 cm⁻¹ 1660 to 1620 cm⁻¹, 1560 cm⁻¹ decomposition point about 140 - 185 o C (decomposition with foaming) ¹H-400MHz (D₂O) 1,807 (dd, H3ax) 2,205 (dd, H3eq) 4,022 (m, H4) 3,901 (t, H5) 3,973 (d, H6) 3,501 (d, H7) 3,747 (m, H8) 3,598 (dd, H9') 3,831 (dd, H9) 2,041 (s, Ac-5) Example 6: Effect of Sodium Salt of N-Acetylneuraminic Acid on Ciliary Movement of Palatine Mucosa of Frog Using the sodium salt of N-acetylneuraminic acid obtained in Example 5, a test was conducted to confirm the above-mentioned effect in accordance with the same testing method as that of Example 1. The result of this test is shown in Table 6. From Table 6, it will be seen that the sodium salt of N-acetylneuraminic acid caused acceleration of the MTR (mucociliary transport rate) i.e. the rate of transport of sputum of the frog palatine mucosa in a certain dependency on the dose. The result was subtantially equivalent to that of the acetylcholine (comparison agent) at a concentration of 10⁻⁴ mg/ml. This suggests that the sodium salt of N-acetylneuraminic acid produces an effect similar to that produced by the above-described calcium salt of N-acetylneuraminic acid. Example 7: Effect of Sodium Salt of N-Acetylneuraminic Acid on Rotary Motion of Ciliated Cell A test was conducted to examine the above-mentioned effect by using sodium salt of N-Acetylneuraminic Acid, in accordance with the same testing method as that of Example 2. The result of this test is shown in Table 7 which shows the following facts. A significant number of rotations was observed upon application of 10⁻³ mg/ml of sodium salt of N-acetylneuraminic acid. Terbutaline showed a general tendency to increase the rotation at a concentration of 10⁻⁴ to 10⁻²mg/ml. Acetylcholine showed an increase in the rotation in a certain dependency on the dose, at a concentration of between 10⁻³ and 10⁻² mg/ml. From these facts, it is understood that the sodium salt of N-acetylneuraminic acid can be used as an expectorant as effectively as the calcium salt of N-acetylneuraminic acid. Example 8 : Effect of Sodium Salt of N-Acetylneuraminic Acid on Sputum The sputum used for the specimens was collected from 12 samples of patients suffering from chronic obstructive lung disease. The sodium salt of N-acetylneuraminic acid was added to the specimen sputum in the ratios of 5 mg/ml sputum and 1 mg/ml sputum, and the specimen was left for 1 hour at 4 o C before measurement. Sputum which had not been treated by the sodium salt of N-acetylneuraminic acid was used as a comparison example. A palatine mucosa obtained from a decapitated frog head was kept at constant temperature and humidity until the mucus liquid of the frog itself depleted. The specimen sputum was placed on the dried palatine mucosa, and the speed of movement of the sputum was observed through a noumenal microscope, thus measuring the MTR. The pH value of the sputum was measured by means of an electronic model HM-SAp pH meter, while the spinnability was measured by a device developed by Nagaoka and Yamanaka (disclosed in Transactions of 2nd Symposium of Cough and sputum, published July 20, 1979). The yield value was measured by Dulfano's double-tube method which is shown in the American Review of Respiratory Diseases, Vol. 104, p88, 1971. The result of this test is shown in Table 8. From Table 8, it will be seen that the samples treated with the sodium salt of N-acetylneuraminic acid (1 mg/ml sputum) showed a significant increase in pH value and MTR. Although the spinnability was generally increased, a reduction was observed with regard to the yield value. From these facts, it is understood that the sodium salt of N-acetylneuraminic acid can be used effectively as an expectorant which increases the viscosity of low viscosity sputum, such as purulent sputum which is difficult to expectorate, to a high level suitable for transport by cilia, thereby facilitating the expectoration. Rheological properties before and after Sodium Salt of N-Acetylneuraminic Acid Treatment of purulent sputum from patients with diffuse panbronchiolitis Treatment Number of specimens Mean±S.D. MTR (mm/min.) before 15 9±5 after 15 12±5 a pH before 15 7.48±0.41 after 15 7.91±0.43 b Yield value, mmH₂O before 15 0.8±1.5 after 15 0.3±0.6 Spinnability, mm before 15 13±14 after 15 21±28 a: P < 0.01 b: P < 0.001 Example 9: Acute Toxicity Test of Sodium Salt of N-Acetylneuraminic Acid A test was conducted to examine the acute toxicity of the sodium salt of N-acetylneuraminic acid, in mice, rats, and guinea pig by means of administration per os, subcutaneous injection, intravenous injection, intraperitoneal injection, and inhalation. (1) Test Animals ICR mice 6 weeks old SD rats 6 weeks old Hartley guinea pig 6 weeks old (2) Application Density 20% (W/V) dissolved in distilled water (3) Number of Test Animals per Level 10 (4) Observation Period 14 days (5) Method of Calculation of LD₅₀ By Probit method The result of the test is shown in Table 9 below. Acute Toxicity Test of Sodium Salt of N-Acetylneuraminic Acid Species LD₅₀ (mg/kg) Way of administration per os subcutaneous injection intraperitoneal injection intravenous injection inhalation mouse >5,000 >5,000 >5,000 6,286 (5,679-7,084) - >5,000 >5,000 >5,000 7,951 (7,214-9,073) - rat >5,000 >5,000 >5,000 2,966 (2,638-3,342) >4,000 mg/m³ >5,000 >5,000 >5,000 >5,000 >4,000 mg/m³ guinea pig - - - 2,856 (2,355-4,087) - Inhalation was conducted by 1-hr exposure to mist. Values in parentheses show 95% reliability limit.

Claims: Claims for the following Contracting States : BE, CH, DE, FR, GB, IT, LI, NL, SE An expectorant capable of directly acting on the ciliated cells of the airway and on the rheological property of sputum, comprising a compound of the following formula: wherein, on condition of n = 1, Z represents lithium, potassium, sodium, ammonium, or organic ammonium, whereas on condition of n = 2, Z represents calcium, barium or magnesium, as an effective component. An expectorant according to claim 1 in the form of an aerosol for inhalation. An expectorant according to claim 2 wherein the dose of the effective component is 0.5 to 5 mg/time. Use of a compound according to claim 1 for the peparation of an expectorant capable of directly acting on the ciliated cells of the airways and on the rheological property of sputum. Claims for the following Contracting State : AT A Process for the preparation of an expectorant capable of directly acting on the ciliated cells of the airway and on the rheological property of sputum, comprising a compound of the following formula: wherein, on condition of n = 1, Z represents lithium, potassium, sodium, ammonium, or organic ammonium, whereas on condition of n = 2, Z represents calcium, barium or magnesium, by neutralizing an N-acetylneuraminic acid with a hydroxide or carbonate of an alkali metal or alkali earth metal and separating the corresponding alkali metal salt or alkali metal salt from the system and formulating this salt in a form which permits the use of a known local administration method. The Process according to claim 1 wherein the expectorant is in the form of an aerosol for inhalation. The Process according to claim 2 wherein the dose of the effective component is 0.5 to 5 mg/time. Use of a compound according to claim 1 for the peparation of an expectorant capable of directly acting on the ciliated cells of the airways and on the rheological property of sputum.

Inventors: HANAFUSA TAKASHI, ITO MASAYOSHI, KARIYA KATSUHIDE, OGASAWARA SADANORI, SHITORI YOSHIYASU, HANAFUSA, TAKASHI, ITO, MASAYOSHI, KARIYA, KATSUHIDE, OGASAWARA, SADANORI, SHITORI, YOSHIYASU
Applicants: KANTO ISHI PHARMA CO LTD, MECT CORPORATION
Application year: 1985
Main classification: A61K31
IPC codes: A61P11, C07H13, A61K31, C07H11