COMPLEX OF PULLULAN AND POLYETHYLENE GLYCOL

Abstract: An association complex, comprising pullulan and polyethylene glycol. The association complex, as well as its pullulan and PEG components, exerts a decreased solubility in water. The association complex reduces or even eliminates the excessively high water-solubility, threading and stickiness of pullulan so that this extends the uses of pullulan and PEG such as those in gradually disintegrable- and sustained release-shaped articles for consumer's products, toiletries, cosmetics, pharmaceuticals and feeds.

Description: The present invention relates to a complex comprising pullulan and polyethylene glycol, and to its preparation and uses. More particularly, the present invention relates to a complex comprising pullulan and polyethylene glycol wherein the pullulan and polyethylene glycol have a decreased water-solubility with respect to the water-solubility of said pullulan and said polyethylene glycol. Throughout this specification, the abbreviation "PEG" means polyethylene glycol, and references to the "complex" should be taken to mean the complex of PEG with pullulan. Pullulan is a viscous glucan produced by culturing a microorganism of the species Aureobasidium pullulans on a nutrient culture medium containing saccharide(s) such as a monosaccharide and lower oligosacchrides under aerobic conditions. Hayashibara Co., Ltd., Okayama, Japan, is the only company that commercializes pullulan on an industrial scale. Since pullulan has characteristic properties such as water-solubility, edibility, transparency, oil-resistance, gas-barrier property, gloss and adhesion, it has been extensively used as a base material for foods, beverages, cosmetics and pharmaceuticals, as well as for the preparation of various shaped articles, for example, granules, tablets, rods, films and sheets. Recently, as in the case of shaped articles for pharmaceutical uses, gradually disintegrable shaped articles that are imparted with a controlled solubility and disintegration rate in an aqueous system in order to retain their efficacy over a prescribed period, and also sustained release shaped articles that gradually release the effective ingredient have been in great demand. Shaped articles containing intact pullulan readily dissolve and disintegrate in water, and as such are not directly suitable for the preparation of gradually disintegrable- and sustained release-shaped articles. In a previous proposal for making sustained release materials incorporating pullulan, as described in Japanese Patent Laid-Open No. 219,238/85, we have proposed a shaped article wherein a heteromannan is incorporated together with pullulan. We have found that the products resulting from our previous proposal have the drawback that their preparation is relatively complicated, and their solubility may be still too high, depending on the use. FR-A-2264896 discloses a method for making a fibre or a filament based on pullulan. Pullulan is described as being soluble in water although under certain conditions pullulan filaments can be made insoluble. This document does not teach that PEG could be mixed with pullulan in certain proportions to yield a complex having reduced water solubility. We investigated complexes comprising pullulan and a water-soluble polymer in order to decrease much more the solubility of pullulan in water. As a result, we have found that when pullulan is allowed to come into contact with water-soluble polymers in an aqueous system, unlike the other water-soluble polymers tested, PEG (commercialized by Nippon Oil & Fats Co., Ltd., Tokyo, Japan, under the trade name of "Macrogol") specifically forms a complex with the pullulan and the respective water-solubilities of pullulan and PEG are very much decreased. Furthermore, the resultant complex can be easily recovered. Accordingly, the present invention provides a complex, comprising pullulan and polyethylene glycol associated on a molecular level via hydrogen bonds and having a decreased water-solubility with respect to the water-solubility of said pullulan and said polyethylene glycol, said polyethylene glycol having a molecular weight in the range of 200-10,000, and the amount of said polyethylene glycol being in the range of 0.01-100 parts by weight with respect to one part by weight of said pullulan, based on the dry solid. Intrinsically, both pullulan and PEG are polymers that are readily soluble in water. The solubility of the complex per se is extremely low in water, and the pullulan and PEG show a decreased water-solubility in the complex. An appropriate amount of the powdered complex gives a white suspension when added in test tube with water. The complex is solubilized with relative ease to release pullulan and PEG by dissolving a relatively large amount of salt or admixing thereto a hydrogen bond destroying agent such as dimethyl sulfoxide, formamide and urea. This suggests that in the complex pullulan molecules and PEG molecules are strongly bound via hydrogen bonds and the bonds are responsible for the deacrease in water-solubility. Preparation of the complex will hereinafter be explained. The complex is obtained by allowing pullulan to come into contact with PEG in an aqueous system, for example, in solution. For example, an aqueous pullulan solution and a liquid PEG are mixed, and the resultant complex in a concentrate or white turbid form is recovered. In this case, with respect to one part by weight of pullulan, 0.01-100 parts by weight, preferably, 0.1-10 parts by weight of PEG, d.s.b., is used. ("d.s.b." is an abbreviation for the term "on a dry solids basis"). Pullulan having a molecular weight in the range of 10,000-5,000,000 can be used in the invention, irrespective of its method of preparation. Any PEG can be used in the invention as long as it is in solution. For example, a liquid PEG with a relatively low molecular weight, for example, 200-600, is used intact or in aqueous solution, while a solid PEG with a relatively high molecular weight, for example, 1,000-10,000, is melted into liquid by heating or prepared into aqueous solution prior to its use. The resultant complex in a concentrate or white turbid form can be easily recovered by decantation, filtration, and/or centrifugal separation. The white gummy complex thus obtained can be directly prepared into a paste, or, if necessary, dried into powder or chips. The complex in an appropriate form, for example, solution, paste or powder, can be incorporated into the compositions and shaped articles of the invention by appropriate processing steps, for example, by adding, mixing, kneading, spraying, soaking, permeation or injection. For example, a complex formed in solution is prepared intact or in admixture with appropriate substance(s) into a liquid or paste composition, for example, cream, paste, ointment, poultice or feed. For the preparation of the complex in solution, one or more appropriate substances can be advantageously added to the complex. Furthermore, the complex can be advantageously separated, recovered, if necessary, dried, pulverized and added with appropriate substance(s) to obtain a solid composition, for example, a gradually disintegrable- or sustained release-shaped articles. Examples of such substances include antibacterial agents, insecticides, coloring agents, flavoring agents, nutrients, bioactive substances, medicaments, inclusion compounds with cyclodextrin, plasticizers, fillers, foaming agents, vehicles, and flame retarters. The gradually disintegrable- or sustained release-shaped articles can be prepared into pulverulent, linear, plane or cubic shapes, for example, granules, fibers, filaments, rods, gauzes, cloth, nonwoven fabric, films, sheets, paper, coating membranes, tubes, capsules, tablets, sponges, or laminated articles. The compositions and shaped articles obtained in this way can be extensively used for or in consumers' products such as toiletries, cosmetics, pharmaceuticals including those for animals, and other orally-usable products, as well as for agriculture, fisheries, forestry, mining and manufacturing industries. When using the complex to prepare injections containing a bioactive substance such as interferon, tumor necrosis factor, interleukin, insulin, growth hormone and tissue plasminogen activator, advantageously the complex gradually releases the bioactive substance and prolongs its efficiency over a long time period when injected or placed intramusclarly or intraperitoneally. The following Experiments are given to explain the complex in more detail. Experiment 1 Behaviour of water-soluble polymers in aqueous pullulan solution Three milliter aliquots of a 30 w/v % aqueous solution of pullulan, average molecular weight of 200,000 were placed in test tubes, and to each aliquot was added a 6 ml aliquot of 20 w/v % aqueous solution of one of the water-soluble polymers as listed in Table I. Formation of the complex was checked by macroscopically observing the amount of white insoluble material occurring with a decrease of water-solubility. The results were as shown in Table I. Water-soluble polymer White turbidity Remarks Polyvinyl alcohol - Control P E G +++ Present invention Sodium polyacrylate - Control Polyvinyl pyrrolidone - Control Carboxymethyl cellulose - Control Dextran - Control Gum arabic - Control Pectin - Control α-Cyclodextrin - Control Maltotriitol - Control Note: (+++) indicates that a large amount of white insoluble material occurs. These data evidently show that, among the water-soluble polymers tested, pullulan forms a complex specifically with PEG. It was found that the association reduces the threading, adhesive and sticky properties which are the demerits of aqueous pullulan solution. Experiment 2 Effect of molecular weight on the formation of the complex Pullulan and PEG were tested for the effect of molecular weight on the formation of the complex. Thirty w/v % aqueous solution of pullulan with one of the average molecular weights listed in Table II and 30 w/v % aqueous solution of PEG with one of the average molecular weights listed in Table II were mixed in accordance with the method in Experiment 1, and the formation of the complex was checked by macroscopically observing the amount of the resultant white insoluble material. The results were as shown in Table II. These data evidently show that the average molecular weight of PEG influences its association with pullulan, as well as that a PEG with an average molecular weight in the range of 200-10,000, preferably, 400-6,000, can be advantageously used in the association. Also was found that the molecular weight of pullulan scarcely influences the association. P E G Pullulan Remarks 100,000 200,000 1,000,000 200 ++ ++ ++ Present invention 400 +++ +++ +++ Present invention 1,200 +++ +++ +++ Present invention 2,000 +++ +++ +++ Present invention 6,000 +++ +++ +++ Present invention 10,000 ++ ++ ++ Present invention 15,000 - - - Control 20,000 - - - Control Experiment 3 Physicochemical properties of the complex An aqueous solution of pullulan, average molecular weight of 200,000, and that of PEG, average molecular weight of 400, were mixed according to the method in Experiment 1, and the resultant complex was recovered by filtration, washed with ethanol, dried and pulverized. (1) A small portion of the complex gives a white suspension when water is added to it in a test tube. The complex is readily solubilized to release pullulan and PEG by heating or adding thereto a relatively large amount of salt or a hydrogen bond destroying agent such as dimethyl sulfoxide, formamide or urea. (2) Carbonization point The complex in powder undergoes carbonization and degradation at 200±20°C when heated. (3) Ultraviolet absorption spectrum No characteristic absorption is observed. (4) Infrared absorption spectrum Intrared absorption spectrum of the complex was determined by the film method. The results were as shown in FIG. 1 As control, the infrared absorption spectra of pullulan and PEG are given respectively in FIGS. 2 and 3. (5) Solubility in solvents Gradually dissolves in cold water. Soluble in hot water, dimethyl sulfoxide and formamide. Scarcely soluble in methanol and ethanol. Insoluble in ethyl ether and petroleum benzine. (6) Coloring reaction Anthrone-sulfuric acid reaction, turned green; ninhydrin reaction, negative; and iodine reaction, turned yellowish brown or greenish brown. (7) Behavior in solution A solution in hot water is neutral or slightly acidic. (8) Appearance White or pale yellow powder. As is evident from the above data, the complex of the invention is a novel composition entirely different from each of the individual materials pullulan and PEG. The following Examples further illustrate the present invention. The Examples describe the preparation and uses of the complex. Example 1 Powder Ten liters of 30 w/v % aqueous solution of pullulan, average molecular weight of 200,000, was added with 3 liters of PEG, average molecular weight of 400, and the resultant white insoluble form was recovered by removing the supernatant by decantation, dried and pulverized to obtain about 4.5 kg of a white powder. Since the product dissolves in water much more slowly than that prepared solely with pullulan, it can be advantageously used in gradually disintegrable- and sustained release-shaped articles. Example 2 Film Twenty liters of 15 w/v % aqueous solution of pullulan, average molecular weight of 800,000, was added with 2 kg of PEG, average molecular weight of 4,000, while heating, and the resultant mixture solution was casted on 60°C chromium coated metal roll. The resultant 0.03 mm thick film was taken off at a rate of 3 meters/minute, and then dried in 90°C air stream. The product is a white and semitransparent film containing a complex of the invention that, unlike pullulan film, did not readily dissolve but gradually disintegrated in an aqueous system. Example 3 Tablet Six parts by weight of a complex in powder, obtained by the method in Example 1, was added with 2 parts by weight of a powdered zinc, and the resultant mixture was prepared with 20 R punch, 12 mm in diameter, into 5.25 mm thick tablets. Since the tablets gradually dissolve and disintegrate without causing a drastic reaction to generate a constant level of hydrogen gas when placed in dilute sulfuric acid, hydrogen gas can be safely generated with the tablets. Example 4 Fertilizer rod A composition fertilizer comprising 14% of nitrogen, 8% of P₂O₅ and 12% of K₂O was added homogenously with 14 parts by weight of a complex powder obtained by the method in Example 1, 5 parts by weight of calcium sulfate and 1 part by weight of water, and the resultant mixture was prepared into rods by heating it to 80°C with an extruder, L/D of 20, compression ratio of 1.8, equipped with 30 mm die. The product is easily handleable and does not necessarily require special packaging. The mechanical strength of the product is sufficient for deep placement. Since after manuring the product gradually dissolves and disintegrates, it is a suitable sustained release fertilizer. Example 5 Dentifrice A dentifrice was prepared by mixing 45.0 w/w % of calcium monohydrogen phosphate, 2.75 w/w % of pullulan (average molecular weight of 400,000), 3.0 w/w % of PEG (average molecular weight of 1,500), 1.5 w/w % of sodium lauryl sulfate, 17.0 w/w % of glycerine, 0.5 w/w % of polyoxyethylene sorbitan monolaurate, 0.05 w/w % of antiseptic, 0.2 w/w % of α-G Sweet, an α-glycosyl stevioside commercialized by Toyo Sugar Refining Co., Ltd., Tokyo, Japan, and 30.0 w/w % of water. The product with a moderate sweetness is a suitable dentifrice for children. The product containing a complex of the invention is an easily handleable dentifrice that is much lower in threading and stickiness than that prepared solely with pullulan. Example 6 Ointment Six hundred grams of pullulan, average molecular weight of 200,000, and 6.5 kg of maltose were dissolved in 3 liters of water by heating, and the resultant mixture was added with 1.2 liters of Macrogol 400 (average molecular weight of 400) containing 20 g of iodine. The resultant was bottled to obtain the captioned product. The product, containing iodine and maltose respectively as disinfectant and nutrient, can be advantageously used as an ointment to treat external wounds such as abrasion, incisure and burn. The product containing a complex of the invention is an easily applicable ointment that is much lower in threading, stickiness and superficial slippiness than that prepared solely with pullulan. As is obvious from the above, the complex of the invention lowers the solubility of pullulan and PEG in water, and this reduces their excessively high solubility in a hydrous system. The present invention reduces the threading and stickiness of pullulan. Incorporation of the complex facilitates preparation of gradually disintegrable- and sustained release-shaped articles, as well as facilitating preparation of cream and ointment that are free of stickiness and superficial slippiness. The complex of the invention will extend the use of pullulan and PEG.

Claims: A complex comprising pullulan and polyethylene glycol associated on a molecular level via hydrogen bonds and having a decreased water-solubility with respect to the water-solubility of said pullulan and said polyethylene glycol, said polyethylene glycol having a molecular weight in the range of 200-10,000, and the amount of said polyethylene glycol being in the range of 0.01-100 parts by weight with respect to one part by weight of said pullulan, based on the dry solid. A process for preparing a complex according to claim 1, said process comprising: contacting pullulan with polyethylene glycol in an aqueous medium to effect association wherein the amount of said polyethylene glycol is in the range of 0.01-100 parts by weight with respect to one part by weight of said pullulan, based on the dry solid, and the molecular weight of said polyethylene glycol is in the range of 200-10,000; and recovering the resultant complex. A process for preparing a composition, which comprises the step of mixing (a) a complex according to claim 1; and (b) at least one additional substance selected from an antibacterial agent, an insecticide, a coloring agent, a flavoring agent, a nutrient, a bioactive substance, a medicament, an inclusion compound with cyclodextrin, a plasticizer, a filler, a foaming agent, a vehicle and a flame retarder. A process according to claim 3, wherein said complex is obtained by contacting pullulan and polyethylene glycol in an aqueous medium to effect association. A process according to claim 3, wherein said composition is a paste. A process according to claim 3, wherein said composition is a sustained release composition or a gradually disintegrable composition when placed in water. A process according to claim 3, wherein said composition is a toiletry, a cosmetic or a pharmaceutical.

Inventors: HIJIYA, HIROMI, MIYAKE, TOSHIO
Applicants: KABUSHIKI KAISHA HAYASHIBARA SEIBUTSU KAGAKU KENKYUJO
Application year: 1987
Main classification: C08L5
IPC codes: A61K8, A61K47, A61K9, C08B37, A61Q11, C08L71, C08L5