the active ingredient of the agent for treating male infertility of the present invention is δ - amino levulinic acid represented by the above general formula ( 1 ), its derivative , or salt thereof . the δ - amino levulinic acids are known to be useful as photosensitizing agents in photodynamic therapy ( published japanese translation of pct international publication no . 2004 - 505105 ), agent for promoting swine growth ( japanese laid - open patent application no . 2003 - 40770 ), agent for improving immune function ( japanese laid - open patent application no . 2006 - 96746 ), etc . however , effect on male infertility has not been known at all . as alkyl group represented by r 1 and r 2 in the general formula ( 1 ), a linear or branched alkyl group with 1 to 24 carbons is preferred , and an alkyl group with 1 to 18 carbons is more preferred , and an alkyl group with 1 to 6 carbons is particularly preferred . examples of alkyl group with 1 to 6 carbons include methyl group , ethyl group , n - propyl group , isopropyl group , n - butyl group and sec - butyl group , etc . as acyl group , a linear or branched alkanoyl group , alkenylcarbonyl group or aroyl group with 1 to 12 carbons is preferred , and an alkanoyl group with 1 to 6 carbons is particularly preferred . examples of the acyl group include an formyl group , acetyl group , propionyl group and butyryl group , etc . as alkoxycarbonyl group , an alkoxycarbonyl group with total carbons of 2 to 13 is preferred , and an alkoxycarbonyl group with 2 to 7 carbons is particularly preferred . examples of the alkoxycarbonyl group include methoxycarbonyl group , ethoxycarbonyl group , n - propoxycarbonyl group and isopropoxycarbonyl group , etc . as aryl group , an aryl group with 6 to 16 carbons is preferred , and examples include phenyl group and naphtyl group , etc . as aralkyl group , a group consisting of an aryl group with 6 to 16 carbons , and the above alkyl group with 1 to 6 carbons is preferred , and examples include benzyl group , etc . as alkoxy group represented by r 3 , a linear or branched alkoxy group with 1 to 24 carbons is preferred , and an alkoxy group with 1 to 16 carbons is more preferred , and an alkoxy group with 1 to 12 carbons is particularly preferred . examples of the alkoxy group include methoxy group , ethoxy group , n - propoxy group , isopropoxy group , n - butoxy group , pentyloxy group , hexyloxy group , octyloxy group , decyloxy group and dodecyloxy group , etc . as acyloxy group , a linear or branched alkanoyloxy group with 1 to 12 carbons is preferred , and an alkanoyloxy group with 1 to 6 carbons is particularly preferred . examples of the acyloxy group include an acetoxy group , propionyloxy group and butyryloxy group , etc . as alkoxycarbonyloxy group , an alkoxycarbonyloxy group with total carbons of 2 to 13 is preferred , and an alkoxycarbonyloxy group with total carbons of 2 to 7 is particularly preferred . examples of the alkoxycarbonyloxy group include a methoxycarbonyloxy group , ethoxycarbonyloxy group , n - propoxycarbonyloxy group and isopropoxycarbonyloxy group , etc . as aryloxy group , an aryloxy group with 6 to 16 carbons is preferred , and examples include phenoxy group and naphtyloxy group , etc . as aralkyloxy group , a group having the above aralkyl group is preferred , and examples include benzyloxy group , etc . in the general formula ( 1 ), as r 1 and r 2 , a hydrogen atom is preferred . as r 3 , a hydroxy group , alkoxy group or aralkyloxy group is preferred , and a hydroxy group or alkoxy group with 1 to 0 . 12 carbons is more preferred . a methoxy group or hexyloxy group is particularly preferred . examples of δ - amino levulinic acid derivatives include . ester derivatives such as δ - amino levulinic acid methyl ester , δ - amino levulinic acid ethyl ester , δ - amino levulinic acid propyl ester , δ - amino levulinic acid butyl ester , δ - amino levulinic acid pentyl ester and δ - amino levulinic acid hexyl ester . particularly , δ - amino levulinic acid methyl ester or δ - amino levulinic acid hexyl ester is preferred . salts of δ - amino levulinic acid or its derivative are not particularly limited , while a pharmaceutically acceptable acid addition salt of an inorganic acid or organic acid is preferred . examples of acid addition salt of an inorganic acid include hydrochloride , hydrobromate , hydrosulfate , nitrate and phosphate . examples of acid addition salt of an organic acid include acetate , lactate , citrate , tartrate , succinate , maleate , fumarate and ascorbate . particularly , δ - amino levulinic acid hydrochloride or δ - amino levulinic acid phosphate is preferred . these salts can be manufactured by chemical synthesis or by a method using microorganisms or enzyme . examples of these methods include methods described in japanese laid - open patent application no . 4 - 9360 , published japanese translation of pct international publication no . 11 - 501914 , japanese laid - open patent application no . 2006 - 182753 , japanese laid - open patent application no . 2005 - 314361 , and japanese laid - open patent application no . 2005 - 314360 . as it is described in the following examples , δ - amino levulinic acid , its derivative or salt thereof have an effect to increase seminal vesicle weight , and to ameliorate erectile dysfunction . therefore , the δ - amino levulinic acid , its derivative or salt thereof are useful for treating male infertility , particularly oligozoospermia and asthenospermia , or erectile dysfunction . further , the agent for treating male infertility of the present invention is preferred to comprise a combination of δ - amino levulinic acid , its derivative or salt thereof , with an iron compound in order to enhance its therapeutic effect . herein , the iron compound is not particularly limited as long as it is a compound comprising iron in its molecule . examples include ferric chloride , iron sesquioxide , sodium iron chlorophyllin , ferritin iron , ferrous citrate , iron sodium citrate , iron ammonium citrate , ferrous fumarate , ferrous pyrophosphate , ferric pyrophosphate , saccharated iron oxide , iron acetate , iron oxalate , ferrous succinate , iron sodium succinate citrate , heme iron , iron dextran , iron lactate , ferrous gluconate , iron sodium diethylenetriaminepentaacetate , iron ammonium diethylenetriaminepentaacetate , iron sodium diethylenediaminetetraacetate , iron ammonium diethylenediaminetetraacetate , iron triethylenetetraamine , iron sodium dicarboxymethylglutamate , and iron ammonium dicarboxymethylglutamate , iron choline citrate , ferrous formate , ferric formate , ferric ammonium potassium oxalate , ferrous sulfate , ferric sulfate , iron ammonium sulfate , ferric carbonate , ferrous chloride , ferric chloride , andiron oxide , etc . these compounds may be used alone or by combining 2 or more of these . as iron compounds , ferrous citrate , ferrous fumarate , ferric pyrophosphate , saccharated iron oxide and iron dextran used commonly for medical use are particularly preferred . in the present invention , the combination ratio of δ - amino levulinic acid , its derivative or salt thereof to iron compound is preferably 1 : 0 . 125 to 1 : 4 as mass ratio , and particularly preferably 1 : 0 . 25 to 1 : 1 . the agent for treating male infertility of the present invention may be prepared by common methods by mixing a pharmaceutically acceptable carrier , for example , an excipient , binding agent , disintegrant , lubricant , coloring agent , flavoring agent , and coating agent according to need to the above components . dosage forms are not particularly limited , and can be appropriately selected according to the therapeutic purpose . examples include formulation for oral administration such as granules , fine grain agent and tablets ; formulation for injection such as liquid agent and powder formulation dissolved before use ; formulation for transdermal administration such as ointment , liquid agent , cream and gel ; and formulation for parental administration such as suppository . methods for administrating these formulations include oral administration , intravenous administration , intramuscular administration , local administration to affected area , intraperitoneal administration , transdermal administration , and intrarectal administration . among these , oral administration , intraperitoneal administration , local administration to affected area , and intravenous administration are preferred . in the present invention , when δ - amino levulinic acid , its derivative , or salt thereof is used in combination with an iron compound , they may be administered at the same time , or they may be administered separately with a time interval . specifically , δ - amino levulinic acid , its derivative or salt thereof and the iron compound may be formulated as a single formulation , or may be used as a set ( kit ) by being formulated separately . when they are formulated separately , they may have a different dosage form . further , the administration frequency of each component may be different . in the present invention , the dosage amount of δ - amino levulinic acid , its derivative or salt thereof , depends on the administration method , symptoms and body weight of the patient , or tumor types . for example , in case of oral administration , the dosage is 0 . 001 mg to 10 g per 1 kg of body weight at one time , preferably 0 . 01 mg to 5 g , more preferably 0 . 1 to 1000 mg , and particularly preferably 1 to 600 mg per 1 kg of body weight . further , the dosage amount of iron compound depends on the administration method , symptoms and body weight of the patient , or tumor types . for example , in case of oral administration , the dosage is 0 . 001 mg to 10 g per 1 kg of body weight at one time , preferably 0 . 01 to 1000 mg , and particularly preferably 0 . 1 to 500 mg per 1 kg of body weight . the timing to administer the agent for treating male infertility of the present invention is not particularly limited as long as , it is administered before performing sexual intercourse , and it is preferred to administer the agent between 90 days before sexual intercourse and the day of sexual intercourse , more preferably between 30 days before and the day of sexual intercourse , and particularly preferably between 10 days before and the day of sexual intercourse . the number of times of administration may be once a day , but may be administered several times a day , not being limited to once a day . when administering the agent for several days , it may be administered continuously or non - continuously during the above period . the diseases being the subject for applying the agent for treating male infertility of the present invention is male infertility in general , and it is particularly preferred to apply the agent to male infertility caused by oligozoospermia and asthenospermia , or to male infertility caused by erectile dysfunction . further , the agent for treating male infertility of the present invention is to be administered to male of mammals , and examples of mammals include human , cattle , swine , sheep , goat , mouse , rat , rabbit , dog and cat . preferred levels of the therapeutic effect of the agent for treating male infertility of the present invention can be suitably exemplified by a conception rate of 85 % or more in the copulated animals in the experiment of example 2 described in the following . a conception rate of 90 % or more can be more preferably exemplified , and 94 % or more can be further preferably exemplified . further , a preferred level in a different embodiment can be exemplified by a sperm motility on day 21 after the administration of the agent of the present invention which is 1 . 5 - fold or more of that of before the administration ( day 0 ), in the experiment described in example 4 in the following . a motility of 2 . 0 - fold or more can be more preferably exemplified , a motility of 3 - fold or more motility can be further preferably exemplified , and a motility of 4 - fold or more can be further more preferably exemplified . further , it can be preferably exemplified by a sperm survival rate (%) on day 21 after the administration of the agent of the present invention which is 1 . 2 - fold or more relative to that of before the administration ( day 0 ). a survival rate of 1 . 5 - fold or more can be more preferably exemplified , and a survival rate of 1 . 8 - fold or more can be further suitably exemplified , and a survival rate of 2 . 1 - fold or more can be further more preferably exemplified . further , the present invention encompasses use of δ - amino levulinic acid , its derivative , or salt thereof and an iron compound in the manufacture of an agent for treating male infertility , use of δ - amino levulinic acid , its derivative , or salt thereof and an iron compound for treating male infertility , and a method for treating male infertility comprising administering δ - amino levulinic acid , its derivative , or salt thereof and an iron compound to mammals ( particularly human ). in the following , the present invention will be explained further by referring to the examples , while the present invention is not limited to these . forty 10 week - old male rats ( slc : wistar ) and forty 9 week - old female rats were obtained , quarantined for 7 days , and were habituated and bred for 13 days . δ - amino levulinic acid ( herein after referred to as ala ) phosphate was weighed , dissolved into injection solvent to prepare a 50 mg / ml solution . the solution was administered orally once a day continuously to twenty 12 week - old male rats for 14 days before crossing , and for 49 to 52 days after crossing until the day before autopsy , by using a sonde for oral administration for rats at a dose of 500 mg / kg ( 500 mg / kg - group ). to the control group , the solution was administered similarly by using an injection solvent to twenty 12 week - old male rats . by making the first day of administration as day 1 , the general state , body weight , ingested amount , autopsy ( weight of the testis , epididymis , seminal vesicle ( including coagulating gland ) and prostate gland ) were observed and measured . as a result , as it is shown in fig1 , concerning the net weight and the weight volume ratio to the body weight of seminal vesicle , the 500 mg / kg - group showed a significant high level compared to the control group . no significant difference was observed for right and left testis , right and left epididymis , and prostate gland . after day 15 from administration of example 1 , crossing period was set as 14 days , and 1 female was housed per 1 male in the control group and in the 500 mg / kg - group . as a result , the conception rate of copulated animals was 80 . 0 % in the control group ( conception succeeded for 16 out of 20 rats ), while it was as high as 94 . 4 % in the 500 mg / kg - group ( conception succeeded for 17 out of 19 rats ; 1 rat died by biting the sonde for oral administration ). 1 g of ala hydrochloride was dissolved into 50 ml of 5 % glucose aqueous solution ( test solution ), and administered to 7 healthy volunteers , married men from 28 to 44 years old . they ingested orally the test solution ( 13 . 9 to 22 . 2 mg / kg ) without taking breakfast . estimation was made according to their individual subjective estimation : specifically , by using their individual sexual experience as a standard ; when erectile promoting sexual intercourse was observed , it was denoted by (◯), when no change is observed by ( δ ), and when the situation was engraved by ( x ). as a result , as it is shown in table 1 , erectile was observed for 5 out of 7 on that night , among which 2 had sexual intercourse , and pregnancy was confirmed . in order to confirm whether the agent for treating male infertility of the present invention ameliorates actually sperm motility and survival rate , the following experiment was conducted by using a dog as a test animal . the dog was a male miniature poodle of age 7 , born on jan . 28 , 2001 . its body weight was 2 . 55 kg when starting the administration of ala . a mixture of ala phosphate and sodium ferrous citrate ( ala phosphate : sodium ferrous citrate = 1 : 4 ( molar ratio ) was prepared as a formulation for administering to this male dog . this formulation was administered orally to this male dog once a day for 21 consecutive days from nov . 27 , 2008 , at a dose of 3 . 33 mg / day in terms of ala phosphate . sperms were collected 3 times from the dog , just before the administration of the formulation ( day 0 ), on day 8 , and on day 21 after the administration . sperms just after collection were observed with a microscope , and the vitality was evaluated on a 5 - point scale . further , sperm motility and survival rate (%) were calculated from the vitality test results . evaluation standard for evaluating the vitality and the evaluation results are shown in the following table 2 . the motility was calculated by setting “+++” as 100 , “++” as 75 , “+” as 50 , “±” as 25 and “−” as 0 , and by using these evaluation values and the ratio of each evaluation level to the evaluation results in the table 2 . for example , the motility on day 0 was calculated by 100 × 0 + 75 × 10 + 50 × 10 + 25 × 20 + 0 × 60 , and by rounding the fractional part to obtain 18 . the survival rate (%) was calculated by determining the evaluation standard “−” as dead sperm , and for other than “−” as living sperm . the motility and survival rate (%) calculated for the collected sperms are shown in table 3 . as it is shown from the results of table 3 , by administrating the formulation of the present invention , both sperm motility and survival rate (%) of the test animal ( dog ) were improved . from these results , it was shown that the formulation of the present invention has a therapeutic effect for oligozoospermia and asthenospermia . the present invention can be used in the field of treatment of male infertility .
the present invention is intended to provide an agent for treating male infertility which is highly effective to male infertility , and having few side effects . to achieve the object , an agent for treating male infertility comprising δ - amino levulinic acid shown by general formula , its derivative or salt thereof : r 2 r 1 nch 2 coch 2 ch 2 cor 3 can be used .