AIDS therapeutic agents comprising polymers formed from cinnamic acid derivatives
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to AIDS therapeutic agents containing a dehydrogenation polymer of a substituted cinnamic acid as an effective ingredient. More particularly, it is concerned with AIDS therapeutic agents comprising a dehydrogenation polymer of a cinnamic acid derivative with a phenyl group having at least one hydroxyl group or a pharmaceutically acceptable salt thereof as an effective ingredient. 
     2. Description of the prior art 
     AIDS (acquired immunodeficiency syndrome) has been spreading worldwide and constitute a social problem. At present, however, no effective AIDS preparation is known. For example, vaccinotherapy is being investigated. However, the denaturating properties of the proteinous portions of HIV-1 or HIV-2, an AIDS-causing virus, make it hard to establish reliable vaccinotherapy. Moreover, nucleic acid analogs such as azidothymidine are not acceptable cures in view of severe side-effects. 
     The inventors of the present invention have found that a substance with a strong anti-virus activity is contained in a water-soluble extract from ligneous materials and lignificated naturally occurring materials. Intense research was made into its components. As a result, a high molecular portion containing lignin has been found to have an anti-virus activity. Separately, it has been reported that lignosulfonic acid, an industrial waste in the pulp industry, has anti-AIDS virus activity. Isolation and purification of pure lignin from natural lignificated materials, though, is extremely difficult. The product is a mixture contaminated with hemicellulose or the like. Accordingly, there is a risk of side-effects due to the contaminants when it is used as a medicine. Furthermore, there is no evidence for the assumption that lignin consitutes an essential active structure closely related with the anti-virus activity or what type of lignin structure is more effective. 
     SUMMARY OF THE INVENTION 
     The inventors of the present invention have found a substance which is similar to naturally occuring lignificated material, but free from contaminants. The substance has anti-AIDS action. This substance is a dehydrogenation polymer of a cinnamic acid derivative. 
     An object of the present invention is the provision of a dehydrogenation polymer of a cinnamic acid derivative which is as an AIDS therapeutic agent, a process for its preparation and an AIDS therapeutic agent comprising the same polymer as an effective ingredient. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a graph showing the correlation between the concentration and activity of DRP-pCA. 
     FIG. 2 is a graph showing the correlation between the concentration and activity of DHP-pFA. 
     FIG. 3 is a graph showing the correlation between the concentration and activity of DHP-CA. 
     FIG. 4 is a graph showing the correlation between the concentration and activity of p-coumaric acid. 
     FIG. 5 is a graph showing the correlation between the concentration and activity of caffeic acid. 
     FIG. 6 is a graph showing the correlation between the concentration and activity of ferulic acid. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The inventors of the present invention synthesized a wide variety of polymers of substituted phenylropanes which were investigated to find a dehydrogenation polymer of a cinnamic acid derivative having a phenyl group substituted with at least one hydroxyl group. 
     The cinnamic acid constituting the polymers of the present invention include cinnamic acid itself and its derivatives having a phenyl substituted with at least one hydroxyl group. Embodiments of such cinnamic acid derivatives are p-coumaric acid, ferulic acid, caffeic acid, umbellic acid, etc. The phenyl may have other substituents which do not present pharmacological issues. The synthesis of the polymers of the present invention may utilize salts, esters and anhydrides of the cinnamic acid derivatives. 
     The polymers of the present invention are synthesized by dehydrogenation polymerization of one or more of such cinnamic acid derivatives. The polymerization may be a copolymerization of a cinnamic acid derivative with a lignin component including p-coumary alcohol, coniferyl alcohol, cinnamyl alcohol, cinabil alcohol and so on. 
     The dehydrogenation polymerization is usually carried out using water as a solvent in the presence of a peroxidase and hydrogen peroxide, 
     Polymerization in the presence of a peroxidase and hydrogen peroxide may be carried out by, for example, two alternative ways. One is dropwise simultaneous addition of an aqueous solution of the cinnamic acid derivative and hydrogen peroxide to an aqueous solution of peroxidase. In the other way, a hydrogen peroxide solution is added dropwise to an aqueous solution containing both the cinnamic acid derivative and a peroxidase. The quantities of the peroxidase and hydrogen peroxide may be arbitrary so long as the selected quantities provide the polymer. Usually hydrogen peroxide is used in the range of 0.5 to 2.0 tools per tool of the cinnamic acid derivative. The quantity of the peroxidase used is within the range for usual enzyme reactions, and crude peroxidases may be used. The reaction temperature may range from 20° to 40° C., and the usual reaction time is 0.5 to 3 hours. 
     The polymers according to the present invention are a mixture of polymers of different degrees of polymerization. The molecular weight is not limited except if the polymer for pharmaceutical purposes, is desired to be a powdery material soluble in a neutral aqueous solution. Then the molecular weight distribution is preferred to Be within the range of around 800 to 150,000 . The polymers within the purview of the present invention have a characteristic aspect in that they are of a network structure constructed by complicated polymerization through intermolecular convalent bonds of phenolic oxygens, phenyl carbons and substituent-bearing carbons contained in the monomer molecules (cinnamic acid derivatives), and they have carboxyl groups on branched chains. Part of the carboxyl groups are thought to form lactones or esters with adjacent phenolic hydroxyl groups in the molecules. 
     I. R. absorption spectrum evidence indicates that the polymers of the present invention have a structure possessing strong absorption bands in the absorption regions of hydrogen-OH bonds (3000 to 3600 cm -1 ), carboxyl C═O bonds (1600 to 1720 cm -1 ) and C--O bonds (100 to 1400 cm -1 ). From I.V. absorption spectrum, the polymers are determined to have a structure which displays absorption maximum at around 280 nm, minimal absorption at around 260 nm, and another absorption gradually lessening to about 700 nm (end-absorption), with intensity of absorption at around 320 nm amplified in an alkaline solution. Furthermore, the polymers according to the present invent ion show strong proton N. M. R. Spectrum absorption and the spectrum is based on hydrogen (around 4 ppm) possessed by aromatic hydrogen (7 to 8 ppm), aliphatic double-bond hydrogen (5 to 6 ppm), O--CH hydrogen (4 to 5 ppm), and when monomers to be used (e.g., ferulic acid) have OCH 3  group, the spectrum is based on these hydrogens (around 4 ppm). In addition, the polymers according to the present invention show intensive E.S.R. spectrum of the powdery state absorption and the E.S.R. spectrum of powdery state is based on an organic free radical at a δ value of 2.003. 
     The polymers according to the present invention have an excellent anti-AIDS virus activity, are less toxic, and are useful as an agent for both treating and preventing AIDS. 
     The polymers according to the present invention may be administered to humans orally or parenterally, for example, by injection. 
     The preparations for oral administration include solids such as tablets, granules, powders, fine subtilaes or hard capsules as well as liquids, e.g., syrup preparations. 
     Such preparations may be made in the conventional manner. Illustratively, tablets, granules, powders and fine subtilaes are prepared by mixing a polymer of the present invention or its pharmaceutically acceptable salt with a conventional additive such as lactic acid, starch, crystalline cellulose, magnesium stearate, hydroxypropylcellulose or talc. Hard capsules may be made by filling capsules with the thus prepared powders or fine subtilaes appropriately. 
     The syrup preparations may be made by dissolving or suspending a polymer according to the present invention or a pharmaceutically acceptable salt thereof into an aqueous solution which contains sucrose, carboxymethyl cellulose, etc. 
     Injections may be prepared by aseptically encapsulating a polymer of the present invention or its pharmaceutically acceptable salt into physiological saline or another agent, for example, vegetable oil, oil emulsion, glycerol or the like. 
     The daily dose of the polymers according to the present invention usually is 1 to 300 mg per kg of body weight for the oral route, whereas the quantity is 0.1 to 100 mg for usual injection administration; the quantity may be given at one time or divided into two or three aliquots for intervallic administration a day. 
     The polymers of the present invention have a strong anti-AIDS virus activity and further have a low toxicity. Moreover, because of the presence of intermolecular carboxyl groups, they have an additional advantage in that water solubility is improved, and their preparations are easy to make. Accordingly, the polymers of the present invention are useful as both a therapeutic agent and a preventive agent against AIDS. 
     Explanation follows of the details of the present invention with reference to the particulars of the synthesis of the polymers and examples of their anti-AIDS virus activity. 
     Preparation: Synthesis of the dehydrogenation polymers of the present invention 
     Detailed explanation follows of the cases where the monomer used is p-coumaric acid, ferulic acid, caffeic acid or coniferyl alcohol. 
     Solutions A, B and C were prepared having the following compositions. 
     Solution A: One gram of a monomer to be polymerized was neutralized with 1N sodium hydroxide followed by addition of a 0.05M phosphate buffer solution (pH 8) to a total volume of 200 ml. 
     Solution B: Several ten milligrams of horseradish peroxidase was dissolved in 200 ml of a 0.05M phosphate buffer solution (pH 8). 
     Solution C: Hydrogen peroxide was dissolved in 200 ml of a 0.05 M phosphate buffer solution (pH 8), and the solution was diluted to 0.1%. 
     Polymerization Method 1 (Endwise method): 
     Two dropping funnels were attached to a three-neck flask containing solution B. Solutions A and C (in a ratio which provided 1.5 equivalents of hydrogen peroxide per the monomer used) were simultaneously added dropwise to solution B through separate funnels at 25° C. for 1 hour. 
     After the addition was completed, stirring was continued for an additional one hour, and then acetic acid was added to the solution to lower its pH to 3. The precipitated solids were collected by centrifugation, and then dissolved in water followed by dialysis and lyophilization. 
     Polymerization Method 2 (Bulk method): 
     Solution C was added dropwise to a solution prepared beforehand by mixing the solutions A and B, at 25° C. for 1 hour. 
     The procedures as in the Endwise method mentioned above were followed to yield a lyophilized sample of the same polymer. 
     Table 1 lists the reaction yields of the polymerization reactions, elementary analysis of the polymers of the present invention, U.V. absorbance, and the quantity of the organic free radicals estimated on the basis of the E.S.R. spectrum. 
     In the Table, DHP-pCA stands for the dehydrogenation polymer of p-coumaric acid, DHP-FA stands for the dehydrogenation polymer of ferulic acid, and DHP-CA stands for the dehydrogenation polymer Of caffeic acid. 
     
                       TABLE 1                                                     
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Properties of the polymers of the present invention                       
Elementary             U.V.      Free radical                             
analysis      Reaction absorbance                                         
                                 (intensity                               
C          H      yields   intensity                                      
                                   of E.S.R.)                             
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Polymers prepared according to the Endwise method:                        
DHP-pCA 63.01  3.67   74%    2.38    0.24                                 
DHP-FA  59.37  4.25   69%    1.66    0.29                                 
DHP-CA  53.29  3.27   60%    1.92    0.76                                 
Polymers prepared according to the Bulk method:                           
DHP-pCA 61.97  3.56   86%    2.51    0.32                                 
DHP-FA  59.69  3.97   69%    1.72    0.29                                 
DHP-CA  53.05  3.14   71%    1.86    1.11                                 
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     EXAMPLE 1 
     Activity against HIV-1 type viruses 
     1. Test compounds: 
     Illustrative demonstration follows of the results of the dehydrogenation polymer each of p-coumaric acid (DHP-pCA), ferulic acid (DHP-FA) and caffeic acid (DHP-CA), 
     2. Test procedure: 
     To a 96-well microtiter plate were added HTLV-IIIB-infected MT-4 cells (2.5×10 4  /well, MOI: 0.01) together with test compounds at various concentrations immediately after the infection. In the same manner virus-uninfected cells were cultured together with test compounds at various concentrations in order to determine the cytotoxicity of the test compounds to MT-4 cells. The culturing was carried out in a CO 2  -incubator at 37° C. for 5 days. The survival cells were counted by the MTT method. The anti-virus activity was expressed in terms of the concentration at which 50% of the cell damage was prevented (EC 50 ) and the concentration at which 50% of cytotoxicity was prevented (CC 50 ). CC 50  %/EC 50  % (SI, selective index) was used as the index of effectiveness. (See Paunels et al., &#34;J. Viro. Methods&#34;, vol. 20, pp.309-321, 1988.) 
     3. Test results 
     
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Test compounds                                                            
             CC.sub.50                                                    
                     EC.sub.50 SI                                         
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DHP-pCA      &gt;100    3.85      &gt;26                                        
DHP-FA       &gt;100    5.42      &gt;18                                        
DHP-CA       &gt;100    7.10      &gt;12                                        
p-coumaric acid                                                           
             &gt;100    &gt;100      ineffective                                
Caffeic acid 2.1     3.1       ineffective (&lt;1)                           
Ferulic acid &gt;100    &gt;100      inefective                                 
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     The correlation between concentration and action observed is shown in FIGS. 1 to 6 wherein the survival rate of the cells is represented by the longitudinal axis, while the axis of abscissa reflects concentration of the test compounds. The results reported in the above Table and FIGS. 1 to 3 show that the drugs according to the present invention have a remarkable antivirus activity. 
     EXAMPLE 2 
     Alternative evidence of inhibit growth of HIV-1 type viruses 
     1. Test compounds 
     Illustrative demonstration follows of the results of the dehydrogenation polymer each of p-coumaric acid (DHP-pCA), ferulic acid (DHP-FA) and caffeic acid (DHP-CA). 
     2. Test procedure: 
     To a 48-well plastic plate were added HIV-infected MT-4 cells (500 μl: 3×10 5  cell/ml) together with test compounds at various concentrations (500 μl). Culturing was carried out in CO 2  -incubator at 37° C. for 5 days, and then the whole of the culture was transferred to a test tube for centrifugation. In order to determine the HIV membrane antigen positive rate by laser flow cytofluorography (FACS), the precipitated cells in free state were reacted with a primary antibody (human anti-HIV positive serum) or a secondary antibody (FITC-labelled anti-human IgG) for 1 hour. After the reaction was completed, the cells were washed and immobilized with formaldehyde to determine the antigen positive cells (F-cells) by FACS. 
     Using non-medicated HIV-infected MT-4 cells as the positive control and HIV-uninfected MT-4 cells as the negative control, the antigen positive rate (% control) for the cultures with the test compound added was calculated according to the following equation (see Nakashima et al., &#34;Antimicrob. Agents Chemother.&#34;, p.311524, 1987). 
     Antigen positive rate=(A-C)/(B-C) 
     wherein 
     A: Medicated infected F-cells&#39; rate 
     B: Nonmedicated infected F-cells&#39; rate 
     C: Nonmedicated uninfected F-cells&#39; rate. 
     3. Test results: 
     The test compounds showed not less than 90% inhibition rate at a concentration of 10 μg/ml or more. 50% effective rates (EC 50  %) are shown below. 
     
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Test compounds  EC.sub.50 (μg/ml)                                      
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DHP-pCA         0.83                                                      
DHP-FA          1.78                                                      
DHP-CA          2.56                                                      
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     EXAMPLE 3 
     Activity against HIV-2 type viruses 
     1. Test compound: Dehydrogenation polymer of caffeic acid (DHP-CA) 
     2. Test procedures: 
     To a 96-well microtiter plate were added HIV-2RODinfected MT-4 cells (2.5×10 4  cells/well, MOI: 0.01) together with test compounds at various concentrations immediately after the infection. In the same manner, virus-uninfected cells were cultured together with the compounds at various concentrations in order to determine the cytotoxicity of the test compounds to MT-4 cells. Culturing was carried out in a CO 2  -incubator at 37° C. for 5 days, an survival cells were counted by the MTT method. The anti-virus activity was expressed in terms of the concentration at which 50% of the cell damage was prevented (EC 50  %) and regarding the concentration at which 50% of the cytotoxicity was prevented CC 50 ). CC 50  %/EC 50  % (SI, selective index) was used as the index of effectiveness. (See Paunels et al., &#34;J. Viro. Methods&#34;, vol. 20, pp. 309-321, 1988.) 
     3. Test results: 
     
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Test compounds                                                            
             CC.sub.50    EC.sub.50                                       
                                 SI                                       
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DHP-CA       174          5.07   34                                       
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