COMPOSITION COMPRISING SWEET POTATO STEM OR LEAF EXTRACT AS ACTIVE INGREDIENT FOR PREVENTION OR TREATMENT OF EAR DISEASE

Abstract

The present disclosure provides a composition containing a sweet potato stem and/or leaf extract for prevention, alleviation, or treatment of an ear disease. The composition according to the present disclosure can suppress hearing loss by effectively inhibiting the increase in hearing threshold due to hearing loss and the damage to hair cells, and is useful for the prevention or treatment of an ear disease, such as hearing loss or ringing in the ears, by having effects of reducing abnormal behavior caused by ringing in the ears and of returning the hearing amplitude to normal, and therefore, the composition can be advantageously used as a pharmaceutical composition or a health functional food.

Claims

1-18. (canceled)

19. A method of treating an ear disease, comprising administering a sweet potato stem extract and/or a sweet potato leaf extract to a subject having an ear disease.

20. The method of claim 19, wherein the sweet potato stem extract is Ipomoea batatas stem extract.

21. The method of claim 19, wherein the sweet potato leaf extract is Ipomoea batatas leaf extract.

22. The method of claim 19, wherein the ear disease is one selected from the group consist of hearing loss, tinnitus and deafness.

23. The method of claim 22, wherein the hearing loss is conductive hearing loss or sensorineural hearing loss.

24. The method of claim 22, wherein the hearing loss is one selected from the group consisting of noise-induced hearing loss, age-related hearing loss(presbycusis), sudden hearing loss, auditory neuropathy due to diabetes, ototoxic hearing loss, traumatic hearing loss, and viral hearing loss.

25. The method of claim 24, wherein the ototoxic hearing loss is caused by administration of any one or more ototoxic drugs selected from the group consisting of gentamicin, streptomycin, kanamycin, neomycin, amikacin, tobramycin, netilmicin, dibekacin, sisomycin, livodomycin, cisplatin, carboplatin, and oxaliplatin.

26. The method of claim 22, wherein the tinnitus is one selected from the group consisting of objective tinnitus, subjective tinnitus, peripheral tinnitus, and central tinnitus.

27. The method of claim 19, wherein the sweet potato stem extract and/or a sweet potato leaf extract is an extract of water, a C.sub.1 to C.sub.4 lower alcohol, or a mixed solvent thereof, or a fraction thereof.

28. The method of claim 27, wherein the C.sub.1 to C.sub.4 lower alcohol is one selected from the group consist of methanol, ethanol, propanol, isopropanol and butanol.

29. The method of claim 27, wherein the extract is an ethanol aqueous solution extract.

30. The method of claim 28, wherein the extract is an 50-90% of ethanol aqueous solution extract.

Description

DESCRIPTION OF DRAWINGS

[0096] FIG. 1 shows the prevention, treatment and improvement effects of a sweet potato stem extract (stems of Ipomoea batatas shown as IBS in the drawings) confirmed by treating hair cells damaged by neomycin with the sweet potato stem extract (NOR: neomycin untreated normal control group, NM: neomycin-induced untreated control group, and IBS 1 μg/mL: 1 μg/mL of sweet potato stem extract-treated group);

[0097] FIG. 2 shows the prevention, treatment and improvement effects of a sweet potato leaf extract (leaves of Ipomoea batatas shown as IBL in the drawings) confirmed by treating hair cells damaged by neomycin with the sweet potato leaf extract (NOR: neomycin untreated normal control group, NM: neomycin-induced untreated control group, and IBL 1 μg/mL: 1 μg/mL of sweet potato leaf extract-treated group);

[0098] FIG. 3 shows the comparison of prevention, treatment and improvement effects of a sweet potato tuberous root extract (tuberous roots of Ipomoea batatas shown as IB in the drawings), a sweet potato stem extract (IBS), a sweet potato leaf extract (IBL) obtained by treating hair cells damaged by neomycin with the sweet potato tuberous root extract, the sweet potato stem extract, and the sweet potato leaf extract (NOR: neomycin untreated normal control group, NM: neomycin-induced untreated control group, IB 1 μg/mL: 1 μg/mL of sweet potato tuberous root extract-treated group, IBS 1 μg/mL: 1 μg/mL of sweet potato stem extract-treated group, and IBL 1 μg/mL: 1 μg/mL of sweet potato leaf extract-treated group);

[0099] FIG. 4 shows the effect of the sweet potato stem extract on hearing threshold after exposure to noise confirmed by presenting a click stimulus sound during an auditory brainstem response test (NIHL, i.e., noise-induced hearing loss: untreated control group after exposure to noise, and IBS 300 mg/kg: experimental group treated with 300 mg/kg of sweet potato stem extract after exposure to noise);

[0100] FIG. 5 shows the effect of the sweet potato stem extract on hearing threshold after exposure to noise confirmed by presenting a 16 kHz pure tone of stimulus sound during the auditory brainstem response test (NIHL: untreated control group after exposure to noise, and IBS 300 mg/kg: experimental group treated with 300 mg/kg of sweet potato stem extract after exposure to noise);

[0101] FIG. 6 shows the effect of the sweet potato leaf extract on hearing threshold after exposure to noise confirmed by presenting a click stimulus sound during the auditory brainstem response test (NIHL: untreated control group after exposure to noise, IBL 300 mg/kg: experimental group treated with 300 mg/kg of sweet potato leaf extract after exposure to noise);

[0102] FIG. 7 shows the effect of the sweet potato leaf extract on hearing threshold after exposure to noise confirmed by presenting a 16 kHz pure tone of stimulus sound during the auditory brainstem response test (NIHL: untreated control group after exposure to noise, and IBL 300 mg/kg: experimental group treated with 300 mg/kg of sweet potato leaf extract after exposure to noise)

[0103] FIG. 8 shows the time taken to pass through a transparent tube underwater and the number of rotations(turning) in the transparent tube when evaluating the sweet potato stem extract (stems of Ipomoea batatas) based on the behavior in an animal model of tinnitus (NOR: tinnitus non-induced control group, SS: tinnitus alone-induced group, IBS 10: experimental group treated with 10 μg/ml of sweet potato stem extract);

[0104] FIG. 9 shows SA ratio results of the tinnitus alone-induced group and the experimental group treated with the sweet potato stem extract in the tinnitus-induced group when evaluating the effect of the sweet potato stem extract in the animal model of tinnitus (SS: tinnitus alone-induced group, and SS+IBS: experimental group treated with sweet potato stem extract in tinnitus-induced group); and

[0105] FIG. 10 is a graph illustrating results of measuring the hearing amplitude using the auditory brainstem response with the click stimulus sound after exposure to noise (NOR: tinnitus non-induced control group, SS: tinnitus alone-induced group, and SS+IBS: experimental group treated with sweet potato stem extract in tinnitus-induced group).

BEST MODE

[0106] Hereinafter, the present disclosure will be described in more detail through Examples. However, these Examples and Experimental Examples are provided for illustrating the present disclosure, and the scope of the present disclosure is not limited to these Examples and Experimental Examples.

Example 1: Preparation of Sweet Potato Stem Extract (Stems of Ipomoea batatas)

[0107] 500 g of sweet potato stems were subjected to primary extraction with 9 L of 70% ethanol at 90° C. for 120 minutes. 4.5 L of 70% ethanol was added again to the primary extract, and the resulting product was secondly extracted at the same temperature for 60 minutes. Then, the extract was filtered and concentrated at 70-80 rpm in a water bath at 40° C. The concentrate was frozen at −50° C. and then freeze-dried for 7 days. After freeze-drying, the product was stored in −50° C. freezer. As a result of the extraction of the total of 500 g of sweet potato stems, it was confirmed that 7.27 g of the extract was obtained, and the yield was 1.5%.

Example 2: Preparation of Sweet Potato Leaf Extract (Leaves of Ipomoea batatas)

[0108] 500 g of sweet potato leaves were subjected to primary extraction with 9 L of 70% ethanol at 90° C. for 120 minutes. 4.5 L of 70% ethanol was added again to the primary extract, and the resulting product was secondly extracted at the same temperature for 60 minutes. Then, the extract was filtered and concentrated at 70-80 rpm in a water bath at 40° C. The concentrate was frozen at −50° C. and then freeze-dried for 7 days. After freeze-drying, the product was stored in −50° C. freezer. As a result of the extraction of the total of 500 g of sweet potato leaves, it was confirmed that 14 g of the extract was obtained, and the yield was 2.8%.

Comparative Example 1: Preparation of Sweet Potato Tuberous Root Extract (Tuberous Roots of Ipomoea batatas)

[0109] 500 g of sweet potato tuberous roots were primarily extracted with 9 L of 70% ethanol at 90° C. for 120 minutes. 4.5 L of 70% ethanol was added again to the primary extract, and the resulting product was secondly extracted at the same temperature for 60 minutes. Then, the extract was filtered and concentrated at 70-80 rpm in a water bath at 40° C. The concentrate was frozen at −50° C. and then freeze-dried for 7 days. After freeze-drying, the product was stored in −50° C. freezer. As a result of the extraction of the total of 500 g of sweet potato tuberous roots, it was confirmed that 9 g of the extract was obtained, and the yield was 1.8%.

[0110] Experimental Example 1: Protective effect of sweet potato stem extract (stems of Ipomoea batatas) on hair cells in ototoxic zebrafish model hair cells reduced by neomycin were treated with the sweet potato stem extract of Example 1 to confirm a protective effect thereof on the hair cells.

[0111] Specifically, zebrafish larvae on Day 6 post fertilization were placed in 24 wells and exposed to 2 μM neomycin for 1 hour. Thereafter, the exposed larvae were exposed with 1 μg/mL of the sweet potato stem extract of Example 1 for 6 hours, and a 0.03% sea salt solution was treated as a control group. For direct observation of hair cells, a fluorescence microscope (Olympus 1×70, Olympus, Japan) was used and the cells were stained with 0.1% YO-PRO for 30 minutes. The zebrafish larvae were anesthetized with 0.02% tricaine, and the hair cells were observed with a fluorescence microscope. Data were analyzed by counting the number of hair cells obtained through the fluorescence microscope.

[0112] Results thereof are shown in FIG. 1.

[0113] As shown in FIG. 1, it was confirmed that the number of hair cells significantly increased in the experimental group treated with the sweet potato stem extract, and from this confirmation, it was proved that the sweet potato stem extract according to the present disclosure had an excellent effect in the prevention, improvement and treatment of hearing loss.

[0114] Experimental Example 2: Protective Effect of Sweet Potato Leaf Extract (Leaves of Ipomoea batatas) on Hair Cells in Ototoxic Zebrafish Model

[0115] hair cells reduced by neomycin were treated with the sweet potato leaf extract of Example 1 to confirm a protective effect thereof on the hair cells.

[0116] Specifically, zebrafish larvae on Day 6 post fertilization were placed in 24 wells and exposed to 2 μM neomycin for 1 hour. Thereafter, the exposed larvae were exposed with 1 μg/mL of the sweet potato leaf extract of Example 1 for 6 hours, and a 0.03% sea salt solution was treated as a control group. For direct observation of hair cells, a fluorescence microscope (Olympus 1×70, Olympus, Japan) was used and the cells were stained with 0.1% YO-PRO for 30 minutes. The zebrafish larvae were anesthetized with 0.02% tricaine, and the hair cells were observed with a fluorescence microscope. Data were analyzed by counting the number of hair cells obtained through the fluorescence microscope.

[0117] Results thereof are shown in FIG. 2.

[0118] As shown in FIG. 2, it was confirmed that the number of hair cells significantly increased in the experimental group treated with the sweet potato leaf extract, and from this confirmation, it was proved that the sweet potato leaf extract according to the present disclosure had an excellent effect in the prevention, improvement and treatment of hearing loss.

[0119] Experimental Example 3: Comparison of protective effect on hair cells damaged by neomycin among sweet potato tuberous root extract (tuberous roots of Ipomoea batatas), sweet potato stem extract, and sweet potato leaf extract in ototoxic zebrafish model

[0120] hair cells reduced by neomycin were treated with the sweet potato stem extract of Example 1, the sweet potato leaf extract of Example 2, and the sweet potato tuberous root extract of Comparative Example 1 to confirm protective effects thereof on the hair cells.

[0121] Specifically, zebrafish larvae on Day 6 post fertilization were placed in 24 wells and exposed to 2 μM neomycin for 1 hour. Thereafter, the exposed larvae were exposed with 1 μg/mL of the sweet potato stem extract of Example 1, the sweet potato leaf extract of Example 2, and the sweet potato tuberous root extract of Comparative Example 1, respectively, for 6 hours, and a 0.03% sea salt solution was treated as a control group. For direct observation of hair cells, a fluorescence microscope (Olympus 1×70, Olympus, Japan) was used and the cells were stained with 0.1% YO-PRO for 30 minutes. The zebrafish larvae were anesthetized with 0.02% tricaine, and the hair cells were observed with a fluorescence microscope. Data were analyzed by counting the number of hair cells obtained through the fluorescence microscope.

[0122] Results thereof are shown in FIG. 3.

[0123] As shown in FIG. 3, it was confirmed that the experimental group treated with the sweet potato tuberous root extract did not increase the number of hair cells, indicating that there was no effect on hearing loss. On the other hand, it was confirmed that the sweet potato stem and leaf extracts according to the present disclosure had an excellent effect in the prevention, improvement and treatment of hearing loss.

[0124] Experimental Example 4: Confirmation of Improvement in Hearing Loss after Exposure to Noise by Sweet Potato Stem Extract

[0125] Experimental Example 4-1. Confirmation of Hearing Threshold Using Click Broadband Click Stimulus Sound

[0126] In order to verify an effect of sweet potato stem extract on a hearing threshold after exposure to noise, an experiment for measuring the hearing threshold was performed using an auditory brainstem response. A method of measuring the auditory brainstem response (ABR) is a method of evaluating a response to a sound by measuring electric energy when a sound stimulus is transmitted as an electrical signal in the auditory nerve. When the sound reaches the auditory nerve through the outer ear, the middle ear, and the cochlea, the response reflects all states of the outer ear, the middle ear, and the cochlea, which reflects the actual sound energy to which the sound energy reaches the brain. The hearing threshold refers to the minimum sensory point of sound that is barely audible. In a normal mouse, the response is observed even to a sound as low as 20 dB on average.

[0127] Specifically, rats to which 300 mg/kg of sweet potato stem extract (IBS) prepared in Example 1 was administered and untreated control rats were divided into three groups of eight rats, respectively, and evaluated. The rats were exposed to a noise, specifically, a 115 dB complex sound, for 90 minutes, and after 24 hours from exposure to noise, the sweet potato stem extract of Example 1 was orally administered at the same time every day. The hearing threshold was evaluated before exposure to noise, on Days 1, 10, and 20 after exposure.

[0128] For the auditory brainstem response test, the rats were anesthetized by intramuscular injection of ketamine (4.57 mg/kg) and xylazine (0.43 mg/kg), and then evaluated while maintaining body temperature at 37±0.5° C. During the auditory brainstem response test, the rats were evaluated with a broadband click stimulus sound as a stimulus sound by lowering the sound gradually by 5 dB from 80 dB, and the smallest sound of the response was set as the threshold.

[0129] Results thereof are shown in FIG. 4.

[0130] As shown in FIG. 4, the group administered with 300 mg/kg of the sweet potato stem extract (IBS) showed a decrease in threshold on Day 20 after exposure to noise, which was 5 dB lower than that of the control group. Thus, the effect of improving hearing was verified.

[0131] Experimental Example 4-2. Confirmation of Hearing Threshold Using 16 kHz TB Stimulus Sound

[0132] In the auditory brainstem response test, the rats were evaluated with a 16 kHz pure tone as a stimulus sound by lowering the sound gradually by 5 dB from 80 dB.

[0133] Results thereof are shown in FIG. 5.

[0134] As shown in FIG. 5, the group administered with 300 mg/kg of the sweet potato stem extract (IBS) showed a decrease in threshold on Day 10 and Day 20 after exposure to noise, which was 10 dB lower than that of the control group. Thus, the significant effect of improving hearing was verified.

[0135] Experimental Example 5: Confirmation of Improvement in Hearing Loss after Exposure to Noise by Sweet Potato Leaf Extract

[0136] Experimental Example 5-1. Confirmation of Hearing Threshold Using Broadband Click Stimulus Sound

[0137] In order to verify an effect of sweet potato leaf extract on a hearing threshold after exposure to noise, an experiment for measuring the hearing threshold was performed using an auditory brainstem response. A method of measuring the auditory brainstem response (ABR) is a method of evaluating a response to a sound by measuring electric energy when a sound stimulus is transmitted as an electrical signal in the auditory nerve. When the sound reaches the auditory nerve through the outer ear, the middle ear, and the cochlea, the response reflects all states of the outer ear, the middle ear, and the cochlea, which reflects the actual sound energy to which the sound energy reaches the brain. The hearing threshold refers to the minimum sensory point of sound that is barely audible. In a normal mouse, the response is observed even to a sound as low as 20 dB on average.

[0138] Specifically, rats to which 300 mg/kg of sweet potato leaf extract (IBL) prepared in Example 2 was administered and untreated control rats were divided into three groups of eight rats, respectively, and evaluated. The rats were exposed to a noise, specifically, a 115 dB complex sound, for 90 minutes, and after 24 hours from exposure to noise, the sweet potato leaf extract of Example 2 was orally administered at the same time every day. The hearing threshold was evaluated before exposure to noise, and on Days 1, 10, 20 and 30 after exposure.

[0139] For the auditory brainstem response test, the rats were anesthetized by intramuscular injection of ketamine (4.57 mg/kg) and xylazine (0.43 mg/kg), and then evaluated while maintaining body temperature at 37±0.5° C. During the auditory brainstem response test, the rats were evaluated by lowering the sound gradually by 5 dB from 80 dB with a broadband click stimulus sound, and the smallest sound of the response was set as the threshold.

[0140] Results thereof are shown in FIG. 6.

[0141] As shown in FIG. 6, the group administered with 300 mg/kg of the sweet potato leaf extract (IBL) showed a decrease in threshold on Day 20 and Day 30 after exposure to noise, which was 10 dB lower than that of the control group. Thus, the effect of improving hearing was verified.

[0142] Experimental Example 5-2. Confirmation of Hearing Threshold Using 16 kHz TB Stimulus Sound

[0143] In the auditory brainstem response test, the rats were evaluated with a 16 kHz pure tone as a stimulus sound by lowering the sound gradually by 5 dB from 80 dB.

[0144] Results thereof are shown in FIG. 7.

[0145] As shown in FIG. 7, the group administered with 300 mg/kg of the sweet potato leaf extract (IBL) showed a decrease in threshold on Day 10, Day 20, and Day 30 after exposure to noise, which was 12 dB lower than that of the control group. Thus, the significant effect of improving hearing was verified.

[0146] Experimental Example 6: Tinnitus Inhibitory Effect of Sweet Potato Stem Extract (Stems of Ipomoea batatas) in Zebrafish Model Suffering from Salicylic Acid-Induced Tinnitus

[0147] The treatment effect on tinnitus was confirmed by employing a behavioral response test that is able to induce and evaluate tinnitus in zebrafish without physical stress.

[0148] Specifically, the zebrafish larvae were divided into a tinnitus non-induced control group (NOR), an experimental group in which tinnitus was induced by exposure to 3 mM salicylic acid for 5 hours (SS), and an experimental group exposed to the sweet potato stem extract prepared in Example 1 for 17 hours immediately after exposure to 3 mM salicylic acid for 5 hours (IBS). Here, for the IBS experimental group, the experiment was performed by exposing the zebrafish larvae to a concentration of 10 μg/ml of the sweet potato stem extract prepared in Example 1 (IBS 10). All experiments were carried out using a 0.03% sea salt solution as a base solution, and all experimental groups were acclimatized to 0.03% sea salt solution for 1 hour immediately before measurement.

[0149] In order to confirm the effect of the sweet potato stem extract prepared in Example 1, the zebrafish exposed to each solution and sweet potato stem extract were allowed to pass through a transparent tube (outer diameter of 25 mm, inner diameter of 21 mm, and total length of 60 cm) located in a water bath (75(W)×45(D)×45(H) cm), and the time taken to pass through the transparent tube and the number of rotations in the transparent tube were analyzed. The water temperature was maintained at 28° C. by installing an underwater heater in the water bath.

[0150] Results thereof are shown in FIG. 8.

[0151] As shown in FIG. 8, it could be confirmed that in the SS group as compared to the NOR group, tinnitus was induced as the time taken to pass through the transparent tube and the number of rotations in the transparent tube increased significantly (###p<0.001 vs. NOR). In the comparison on IBS efficacy, it was confirmed in the IBS 10 group that tinnitus was suppressed as the time taken to pass through the transparent tube and the number of rotations in the transparent tube were significantly lowered (***p<0.001 vs. SS).

[0152] Experimental Example 7: Skinner behavioral analysis of sweet potato stem extract (stems of Ipomoea batatas) in rat model suffering from salicylic acid-induced tinnitus

[0153] In the Skinner behavioral analysis with trained rats, tinnitus-induced animals tend to have an increased trigger-pressing response in the absence of cue tone. At this time, tinnitus induction may be confirmed in animals by mistaking the tinnitus sound as the cue tone and pressing the trigger. Here, a true positive refers to the number of times the trigger is pressed to acquire food when the cue tone is provided, and a false positive refers to the number of times the trigger is pressed when the cue tone is not provided.

[0154] Rats were divided into three groups each having three rats: a tinnitus non-induced control group (NOR), a tinnitus-induced group (SS), and an experimental group administered with sweet potato stem extract (SS+IBS), and evaluated with the sweet potato stem extract prepared in Example 1.

[0155] In the experiment, the SS group and the IBS group used salicylic acid, which is generally used for a tinnitus-inducing animal model, wherein the salicylic acid was orally administered at a dose of 350 mg/kg 3 hours before the test. The SS group was tested by oral administration of only salicylic acid, and the SS+IBS group was orally administered with salicylic acid 1 hour and 30 minutes before the test with 100 mg/kg of the sweet potato stem extract prepared in Example 1 after inducing tinnitus.

[0156] The test schedule was carried out as follows: 1 day before administration (Base), 3 days (Days 1-3) after simultaneous administration with salicylic acid, and 3 days (Days 4-6) during the tinnitus recovery period. For the SS group, on days 1 to 3, salicylic acid was administered 3 hours before the test and then water was administered 1 hour and 30 minutes before the test, and on days 4 to 6, only water was orally administered 1 hour and 30 minutes before the test. For the SS+IBS group, on days 1 to 3, salicylic acid was administered 3 hours before the test, and the sweet potato stem extract was administered 1 hour and 30 minutes before the test, and on days 4 to 6, only the sweet potato stem extract was administered 1 hour and 30 minutes before the test.

[0157] For behavioral response analysis, silence activity ratio (SA ratio) and false positive ratio (FP ratio) values were used. The SA ratio is calculated by dividing the number of responses when there is no cue tone by the number of responses during the time the cue tone is provided, and the FP ratio is calculated as the ratio of the number of responses in the absence of cue tone to the total number of responses.

[0158] Results thereof are shown in FIG. 9.

[0159] As shown in FIG. 9, it could be confirmed in the SS group that tinnitus was induced by significantly increasing the SA ratio and FP ratio compared to the Base (Day 0). In the SS+IBS group administered orally with the sweet potato stem extract, the SA ratio and the FP ratio were significantly decreased compared to SS group on Day 1 and 2, confirming that tinnitus was suppressed (*p<0.05 vs SS, **p<0.01 vs SS), and on Days 3 to 5, there was no significant decrease, but tinnitus symptoms tended to decrease compared to the SS group. In addition, it could be confirmed that the SA ratio was significantly decreased on Day 6, and the tinnitus symptoms were continuously suppressed when IBS was administered orally (**p<0.01 vs SS).

[0160] Experimental Example 8: Confirmation of Hearing Amplitude of Sweet Potato Stem Extract (Stems of Ipomoea batatas) in Tinnitus Rat Model

[0161] A hearing amplitude measurement experiment using an auditory brainstem response was performed to confirm the effect of sweet potato stem extract on the sense as to the presence or absence of the sound by measuring the hearing amplitude after inducing tinnitus.

[0162] A method of measuring the auditory brainstem response (ABR) is a method of evaluating a response to a sound by measuring electric energy when a sound stimulus is transmitted as an electrical signal in the auditory nerve. When the sound reaches the auditory nerve through the outer ear, the middle ear, and the cochlea, the response reflects all states of the outer ear, the middle ear, and the cochlea and reflects the actual sound energy to which the sound energy reaches the brain. The hearing threshold refers to the minimum sensory point of sound that is barely audible. In a normal mouse, the response is observed even to a sound as low as 20 dB on average.

[0163] When measuring hearing amplitude, 5 amplitudes are usually observed (unit: μV, Wave I to Wave V). Amplitude 1 to 3 (Wave I to III) are formed by auditory branches extending from the 8th cranial nerve and lower nerves. Here, amplitude 1 is generated from the dendrites of the auditory nerve fibers, amplitude 2 is generated from the cochlear nucleus, and amplitude 3 represents the activity level of the superior olivary complex that receives auditory information from the cochlear nucleus. In addition, amplitude 4 and amplitude 5 (Wave IV and V) are formed from the upper brainstem and are related to the lateral lemniscus.

[0164] The schedule and experimental group before the click stimulus test were the same as those of Example 7, and the click stimulus test was performed and evaluated on the 5th day after oral administration of the sweet potato stem extract.

[0165] For the auditory brainstem response test, the rats were anesthetized by intramuscular injection of ketamine (11.43 mg/kg) and xylazine (1.08 mg/kg), and then evaluated while maintaining body temperature at 37±0.5° C. During the auditory brainstem response test, the rats were evaluated by lowering the sound gradually from 90 dB by 5 dB with a broadband click stimulus sound, and the smallest sound of the response was set as the threshold.

[0166] Results thereof are shown in FIG. 10.

[0167] As shown in FIG. 10, the SS group showed an overall increase in amplitude compared to the NOR group, and in particular, it could be confirmed that tinnitus was induced by a significant increase in amplitudes 1 and 5 (*p<0.05 vs NOR, ***p<0.001 vs NOR). The SS+IBS group showed an overall decrease in amplitude compared to the SS group, and in particular, it could be confirmed that the tinnitus symptoms were suppressed by a significant decrease in amplitudes 1, 4, and 5 (*p<0.05 vs SS, **p<0.01 vs SS).

[0168] As described above, it could be confirmed that in the sweet potato stem extract group, the false positive ratio due to tinnitus during the behavioral response test was almost similar to that of normal group, and thus that tinnitus was suppressed. Therefore, the sweet potato stem extract is usable for the prevention, improvement and treatment of tinnitus.

[0169] [Preparation Example]

[0170] The following formulations were prepared using the sweet potato stem and/or leaf extract of Example 1. However, the following Preparation Examples are provided to illustrate the present disclosure, and the content of the present disclosure is not limited thereto.

[0171] Preparation Example 1: Preparation of Tablet

TABLE-US-00001 Sweet potato stem and/or leaf extract 1000 mg  Lactose 100 mg Starch 100 mg Magnesium stearate appropriate amount

[0172] A tablet was prepared by mixing and tableting the above-described ingredients according to a conventional tablet preparation method.

[0173] Preparation Example 2: Preparation of Liquid

TABLE-US-00002 Sweet potato stem and/or leaf extract 1000 mg CMC-Na 20 g Isomerized glucose 20 g Lemon flavor appropriate amount

[0174] Purified water was added to adjust the total volume to 1000 ml. A liquid was prepared by mixing the above-described ingredients and filling the mixture in a brown bottle, followed by sterilization according to a conventional liquid preparation method.

[0175] Preparation Example 3: Preparation of Capsule

TABLE-US-00003 Sweet potato stem and/or leaf extract 1000 mg Crystalline cellulose 3 mg Lactose 14.8 mg Magnesium stearate 0.2 mg

[0176] A capsule was prepared by mixing the above-described ingredients and filling the mixture in a gelatin capsule according to a conventional capsule preparation method.

[0177] Preparation Example 4: Preparation of Injection

TABLE-US-00004 Sweet potato stem and/or leaf extract 1000 mg Mannitol 180 mg Sterile distilled water for injection 2974 mg Na.sub.2HPO.sub.412H.sub.2O 26 mg

[0178] An injection was prepared with the above component content per 1 ampoule (2 ml) according to a conventional injection preparation method.

[0179] Preparation Example 5: Preparation of Health Functional Beverage

TABLE-US-00005 Sweet potato stem and/or leaf extract 100 mg Citric acid 1000 mg Oligosaccharide 100 g Plum Concentrate 2 g Total content with purified water added 900 mL

[0180] A health functional beverage was prepared by mixing the above-described ingredients according to a conventional health functional beverage preparation method.