JP2024508524A - Cosmetic composition for skin improvement through regulation of porphyrin production by skin resident bacteria and regulation of hyaluronic acid degrading enzyme - Google Patents

Abstract

In this disclosure, the growth of indigenous skin bacteria that are bad for skin health and the production of porphyrins, which are harmful factors, are reduced, while the growth of indigenous skin bacteria that does not have a negative impact on skin health is not affected. To provide a cosmetic composition capable of healthy rebalancing of a microbiome. This disclosure also provides a cosmetic composition that can suppress porphyrin production in a porphyrin-producing bacterial strain. Furthermore, this disclosure provides a skin improving composition that suppresses the activity of hyaluronic acid degrading enzyme secreted by skin resident bacteria and suppresses the decomposition of hyaluronic acid in the skin, thereby contributing to moisturizing and preventing aging. do.

Description

This application claims priority based on Korean Patent Application No. 10-2021-0028329 filed on March 3, 2021, and all contents disclosed in the specification and drawings of this application are incorporated into this application. It will be done.

The present invention relates to a cosmetic composition that can beneficially regulate (rebalance) the growth and metabolites of skin resident bacteria. The present invention also relates to a cosmetic composition capable of suppressing the production of skin harmful substances such as suppression of porphyrin production in porphyrin-producing bacterial strains, and suppressing the hyaluronic acid decomposition ability of bacterial strains that secrete hyaluronic acid degrading enzymes.

The skin is home to millions of bacteria, molds, and viruses that make up the skin microbiome. Microbiome (microbiome) refers to a population of microorganisms that exist under a specific environment. The number of microbial genes present in the human body is several hundred times that of human genes, and they influence various functions within the human body.

Most of the human microbiome is said to exist in the intestines, but various microorganisms also exist on the skin. Microorganisms present on the skin, much like the microorganisms in the intestines, play an essential role in various metabolisms such as invasion of pathogens, regulation of the immune system, and decomposition of natural products, and influence human health. It is said that there is a risk of causing The skin, the largest organ of the human body, is colonized by beneficial microorganisms and acts as a physical barrier to prevent pathogens from entering. When the barrier is weakened or the balance between symbionts and pathogens disrupted, skin or systemic diseases can develop. Studying the composition of the microbiome of human skin sites is useful in determining the etiology of common skin diseases or their correlation with skin conditions.

When using disinfectants or antibiotics with strong bactericidal properties that are capable of eliminating the skin's entire indigenous microbial community, there is a risk that bacteria that have a beneficial effect on the skin will also be eliminated, leading to the development of resistant bacteria to the component. There is a possibility that the appearance and proliferation may be promoted. Additionally, when the use of disinfectants or antibiotics is discontinued, the balance of existing skin flora is disrupted, and there is a risk that unwanted bacteria may preferentially grow on the skin, leading to opportunistic infections. If selective flora-modulating agents are used instead of broad-spectrum antibiotics, the proportion of bacteria with beneficial effects on the skin can be increased while avoiding widespread side effects on the skin's native microbial community. .

That is, disruption of the balance between beneficial and harmful bacteria present on the skin may lead to opportunistic infections. Therefore, maintaining the balance between microorganisms is an important part of maintaining a healthy skin condition.

Cutibacterium acnes (C. acnes, commonly known as C. acnes) plays a role in suppressing the invasion and growth of pathogenic bacteria by breaking down sebum into glycerol and fatty acids to keep the skin slightly acidic. fulfill. It is one of the main bacterial species that always reside on the skin, and plays an important role in maintaining the skin barrier. Therefore, it is undesirable to apply to the skin antibiotics that have antibacterial or bactericidal effects that may affect the total C. acnes bacteria.

In recent years, phylogenetic analyzes of B. acnes have been carried out, and it has been found that C. acnes is more prevalent in healthy individuals than in acne vulgaris patients. C. acnes (C. acnes) strains and C. acnes strains that are absent from healthy skin but present primarily in acne patients. It has been revealed that there is a strain of P. acnes. Also, C. Depending on the strain, P. acnes has different properties in secreting harmful molecules such as proteases, lipases, hemolysins, and porphyrins, which degrade host tissues and induce inflammatory responses. May cause adverse skin reactions.

As an example, porphyrin values are observed to be higher in acne-prone skin when compared to healthy skin, and higher in acne lesions compared to non-lesioned areas of acne patients. In particular, C. P. acnes strains are said to produce even higher concentrations of porphyrins. It is also said that there is a possibility that Staphylococcus aureus, which is considered a problem in atopic dermatitis and wound infections, may also produce porphyrins.

Porphyrins not only induce oxidative stress in the skin and promote the expression of inflammatory cytokines in keratinocytes, but also induce a carbonylation reaction, which is a type of protein oxidation, resulting in dark skin tone and unhealthy skin. There is a risk that it will be seen. Therefore, it is used as a measurement index in a wide variety of skin measuring instruments, and needs to be regulated as one of the main harmful factors of skin microorganisms.

Therefore, the problem to be solved by the present invention is to suppress resident skin bacteria (e.g., specific C. acnes strains) that have a relatively negative effect on the skin such as the development of acne, and to have no major effect on the skin. To provide a cosmetic composition capable of rebalancing the flora of skin resident bacteria, since the effect on the growth of skin resident bacteria (for example, a specific C. acnes strain) is relatively small. It is.

Another problem to be solved by the present invention is to provide a skin improvement composition that suppresses the production of porphyrin secreted by microorganisms present in the skin and regulates harmful skin factors that induce oxidative stress and inflammation in the skin. It is to provide.

Still another problem to be solved by the present invention is to provide a skin improvement composition that can prevent the decomposition of hyaluronic acid by inhibiting hyaluronic acid degrading enzymes secreted by microorganisms. .

In order to solve the above-mentioned problems, this disclosure provides at least one selected from the group consisting of thiamin or a cosmetically acceptable salt thereof and saccharide isomerate (mixed high-fructose sugar). Provided is a cosmetic composition for regulating skin microbiome, which contains the cosmetic composition as an active ingredient.

Another aspect of this disclosure is to improve the skin microbiome, which contains as an active ingredient any one or more selected from the group consisting of thiamin or a cosmetically acceptable salt thereof and saccharide isomerate. ) provides a cosmetic composition for controlling Cutibacterium acnes.

According to one aspect of this disclosure, the cosmetic composition according to the present invention can be used for skin improvement through regulation of porphyrin production and/or regulation of hyaluronic acid degrading enzyme in skin resident bacteria. be. Therefore, one aspect of the present disclosure provides a composition for improving skin that suppresses the production of porphyrin secreted by microorganisms present in the skin and regulates harmful skin factors that induce oxidative stress and inflammation in the skin. Another aspect of this disclosure provides a composition for improving skin that can prevent the decomposition of hyaluronic acid by inhibiting hyaluronic acid degrading enzymes secreted by microorganisms.

Preferably, the cosmetic composition according to this disclosure contains thiamine or a cosmetically acceptable salt thereof as an active ingredient.

The present inventors have tested various substances such as amino acids, amino acid derivatives, extracts, saccharides, vitamins, and flavor ingredients, and have confirmed that only the compounds of the present invention exhibit the effects targeted by the present invention. It was completed.

Fitz-Gibbon, S. etc. , (2013). Propionibacterium acnes Strain Populations in the Human Skin Microbiome Associated with Acne. According to Journal of Investigative Dermatology, 133(9), 2152-2160, etc., C. Acne is divided into the following types, and among these, ribotype 4 (RT4) and 5 (RT5) are known to be acne-inducing types, and ribotype 6 (RT6) is It is known to be present in large amounts in healthy skin.

Bacterial strains such as HL053PA1 produce excessive amounts of porphyrins that can induce inflammation and oxidative stress, which may induce the secretion of inflammatory cytokines in the skin and cause inflammation such as acne. The cosmetic composition of this disclosure comprises C.I. Among P. acnes strains, the growth of acne-inducing types (e.g., ribotype 4 (RT4) or 5 (RT5), type IA when based on recA type) is suppressed, and the growth of non-acnegenic types (e.g., ribotype 6) is suppressed. (RT6) has relatively little effect on growth, so the microbiome ecology of the dominant species can be maintained.

In addition, the cosmetic composition of this disclosure suppresses the production of porphyrins by bacteria resident on the skin, particularly acne-inducing type C. By inhibiting the production of porphyrins in P. acnes strains or porphyrins in strains such as Staphylococcus aureus, the induction of acne may be suppressed, the dermal density of the skin may be increased, and dryness symptoms of the skin may be improved; It helps greatly in improving skin tone.

According to recent research, strains belonging to RT6 (or type II when based on recA type) produce relatively few amounts of various harmful factors such as porphyrins, but excessively produce hyaluronan degrading enzymes. It is known that it can be done. It is also known that various bacteria such as Staphylococcus aureus can produce hyaluronan degrading enzymes.

From this point of view, the cosmetic composition of the present disclosure suppresses the decomposition of hyaluronic acid by bacteria resident on the skin, and in particular suppresses the decomposition of hyaluronic acid by non-acnegenic type C. It can exhibit very beneficial effects as a cosmetic composition, such as improving skin elasticity by inhibiting the decomposition of hyaluronic acid by P. acnes strains or Staphylococcus aureus. In addition, such suppression of hyaluronic acid decomposition ability improves dermal density and has outstanding effects on moisturizing and preventing aging.

"Cosmetically acceptable salts" in the present invention include salts of active compounds prepared from relatively non-toxic acids. Acid addition salts are obtained by contacting the neutral form of such compounds with a sufficient amount of the desired acid, pure or in a suitable inert solvent. Examples of cosmetically acceptable acid addition salts include acetic acid, propionic acid, isobutyric acid, oxalic acid, maleic acid, malonic acid, benzoic acid, succinic acid, Suberic acid, fumaric acid, mandelic acid, phthalic acid, benzenesulfonic acid, p-tolylsulfonic acid ic acid), citric acid, tartaric acid Hydrogen chloride, hydrogen bromide, nitric acid, carbonic acid, monohydrogencarbonic acid, phosphorus, as well as salts derived from relatively non-toxic organic acids including, methanesulfonic acid, and its analogs. phosphoric acids, monohydrogen phosphoric acid, dihydrogen phosphoric acid, sulfur acid, monohydrogen sulfur acid, hydrogen iodide or phosphorous acid and their analogs. It also includes salts of amino acids such as arginate and its analogs and analogs of organic acids such as glucuronic acid or galactunoric acid and its analogs. Other examples of salts can be gleaned from the known literature in the field to which the present invention pertains.

In the cosmetic composition according to the present invention, the total content of the active ingredients is preferably 0.00001 to 10% by weight based on the total weight of the cosmetic composition.

The active ingredients of the present invention may exist not only in solvated forms, including forms such as hydrates and ethanolates, but also in unsolvated forms. The active ingredients of the present invention may exist in crystalline or amorphous form, and all these physical forms are included within the scope of the present invention.

Cosmetic compositions according to the present invention include solutions, external ointments, creams, foams, nutritional lotions, softening lotions, packs, softening waters, emulsions, makeup bases, essences, soaps, liquid cleansers, Bath additives, sunscreen creams, sunscreen oils, suspensions, emulsions, pastes, gels, lotions, powders, soaps, makeup removers containing surfactants, oils, powdered foundations, emulsion foundations, waxed foundations It can be manufactured into a dosage form selected from the group consisting of, but not limited to, a patch, a patch, and a spray.

In addition, the cosmetic composition of the present invention may further contain one or more cosmetically acceptable carriers that are commonly incorporated into skin cosmetics, such as oil, water, surfactants, Moisturizers, lower alcohols, thickeners, chelating agents, pigments, preservatives, fragrances, and the like can be added as appropriate, but are not limited to these.

The cosmetically acceptable carrier contained in the cosmetic composition of the present invention varies depending on the dosage form. When the dosage form of the present invention is an ointment, paste, cream or gel, the carrier ingredients include animal oil, vegetable oil, wax, paraffin, starch, tracanth, cellulose derivatives, polyethylene glycol, silicone, bentonite, silica. , talc, zinc oxide or mixtures thereof.

When the dosage form of the invention is a powder or a spray, lactose, talc, silica, aluminum hydroxide, calcium silicate, polyamide powder or mixtures thereof can be used as carrier components, especially when the dosage form is a spray. may further contain propellants such as chlorofluorohydrocarbon, propane/butane or dimethyl ether.

When the dosage form of the invention is a solution or emulsion, a solvent, solubilizer, or emulsifying agent is used as carrier component, such as water, ethanol, isopropanol, ethyl carbonate, ethyl acetate, benzyl Mention may be made of benzoates, propylene glycol, 1,3-butyl glycol oils, in particular cotton oil, peanut oil, corn oil, olive oil, castor oil and sesame oil, fatty acid esters of glycerol fatty esters, polyethylene glycol or sorbitan.

When the dosage form of the present invention is a suspension, carrier components include water, liquid diluents such as ethanol or propylene glycol, ethoxylated isostearyl alcohol, polyoxyethylene sorbitol esters and polyoxyethylene sorbitan esters. Suspending agents such as microcrystalline cellulose, aluminum metahydroxide, bentonite, aga or tracanth are available.

When the dosage form of the present invention is a soap, carrier components include alkali metal salts of fatty acids, fatty acid hemiester salts, fatty acid protein hydrolysates, isethionates, lanolin derivatives, fatty alcohols, vegetable oils, glycerol, sugars, etc. is available.

All the ingredients described in the present invention are preferably used in relevant laws and regulations of Korea, China, the United States, Europe, Japan, etc. (e.g. regulations regarding cosmetic safety standards (Korea), cosmetic safety technical standards (China), food standards). (Korea), Food Additives Authority (Korea), Health and Functional Food Authority (Korea), Hygiene Standards (China), etc.). That is, preferably, the cosmetics, foods, or personal care compositions according to the present invention contain the ingredients according to the present invention within the content limits permitted by the relevant laws and regulations of each country.

The compositions provided in this disclosure, particularly the cosmetic compositions, are suitable for use with skin's main resident bacteria, such as C. Among acne patients, C. Shows the effect of suppressing acne-type growth and the production of harmful factors (porphyrins). In addition, C. While it does not affect the growth of acnes-type bacteria, it can be shown to be effective in inhibiting the activity of hyaluronidase produced by this strain. Furthermore, in addition to P. acnes strains, it can exhibit the effect of suppressing the production of porphyrins and/or hyaluronidase activity produced by bacteria present on the skin such as Staphylococcus aureus.

The drawings attached to this specification illustrate the preferred embodiments of the present invention, and serve to further understand the technical idea of the present invention as well as the contents of the invention. The interpretation should not be limited to the matters shown in the drawings.

These are the results of evaluating the effects of thiamine salts on pathogenic strains of Cutibacterium acnes. These are the results of evaluating the effects of thiamine salts on non-pathogenic strains of Cutibacterium acnes. These are the results of evaluating the effects of thiamine salts on porphyrin production in pathogenic and non-pathogenic strains of Cutibacterium acnes. These are the results of evaluating the effect of thiamine salts on porphyrin production in Staphylococcus aureus strains. These are the results of evaluating the effect of thiamine salt on the hyaluronic acid decomposition ability of a non-pathogenic strain of Cutibacterium acnes. These are the results of evaluating the effect of thiamine salt on the hyaluronic acid decomposition ability of Staphylococcus aureus strains. These are the results of evaluating the effects of saccharide isomerate on the growth of pathogenic and non-pathogenic strains of Cutibacterium acnes and on the production of porphyrins of pathogenic strains of Cutibacterium acnes. In FIG. 7, (a) shows acne skin-related C. The results are the results of evaluating the influence on the growth of the C. acnes strain HL053PA1, and (b) is a healthy skin-related C. acnes strain. The results are the results of evaluating the influence of the C. acnes strain HL110PA3 on the growth of the C. acnes strain. The results are the results of evaluating the influence of C. acnes strain HL053PA1 on porphyrin production, and (d) shows the effect of C. acnes strain HL053PA1 on porphyrin production. These are the results of evaluating the influence of P. acnes strain HL110PA3 on the decomposition rate of hyaluronic acid.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples in order to assist in understanding the present invention. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the following embodiments. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

For reference, materials and methods other than those specifically mentioned in the experimental methods below can be found in the paper "Vitamin B12 modulates the transcriptome of the skin microbiota in acne pathology" (Sci Transl. ed. 2015 Jun 24 ;7(293):293ra103.doi:10.1126/scitranslmed.aab2009.) or “The Skin Bacterium Propionibacterium acnes Employs Two Variants of H Yaluronate Lyase with Distinct Properties” (Microorganisms. 2017 Sep 12;5(3):57. Selection and implementation were made with reference to doi: 10.3390/microorganisms5030057.).

1. Acne-related C. Inhibition of growth of P. acnes strains (Figure 1)
Experimental method: Thiamine HCl is effective against acne-related C. An experiment was conducted to confirm the effect on acne growth.

The HL053PA1 strain, which is a Cutibacterium acnes type mainly present in acne patients, was cultured and activated in a BHI liquid medium, and then re-inoculated to the same turbidity. At this time, the cells were treated with thiamine HCl at a concentration of 1 w/v%, cultured for 7 days, and then the absorbance at 595 nm was measured to confirm the effect on the growth of the bacterial strain. The results are shown in Figure 1.

Results: When treated with thiamine HCl, the growth decreased by about 70% compared to the untreated group, and C. It was confirmed that it suppresses acne-type growth.

2. Normal skin related type C. Growth of P. acnes strain (Figure 2)
Experimental method: Thiamin HCl is a C. An experiment was conducted to confirm the effect on acne type proliferation.

C. which mainly exists only in normal skin. P. acnes type HL110PA3 strain was cultured and activated in a BHI liquid medium, and then re-inoculated to the same turbidity. At this time, the cells were treated with thiamine HCl at a concentration of 1%, and after culturing for 7 days, the absorbance at 595 nm was measured to confirm the effect on the growth of the bacterial strain. The results are shown in FIG.

Results: Acne-related C. It definitely reduced the growth of acne type C. It was not possible to significantly affect the growth of acnes type.

3. Effect of suppressing porphyrin production (Figure 3)
Experimental method: An experiment was conducted to investigate the effect of oxidative stress on the production of porphyrin, which is known to be involved in inflammation such as acne in the skin.

C. P. acnes HL053PA1 and HL110PA3 strains were cultured and activated in BHI liquid medium, respectively, and then re-inoculated to the same turbidity. At this time, the cells were treated with thiamine HCl at a concentration of 1%, and after culturing for 7 days, the bacterial strain culture was collected. 400 μl of bacterial culture was extracted with ethyl acetate and acetic acid (4:1, vol/vol). The extract was centrifuged to separate the layers, and a supernatant (upper layer) containing porphyrin was collected. 1.5M HCl was added to the collected supernatant to dissolve it, and centrifugation was performed to separate the layers, and the lower layer was collected. Fluorescence was measured at 405 nm/620 nm for the collected soluble phase. The results are shown in FIG.

Results: Acne-related C. P. acnes strains are C. acnes strains that normally exist on skin. produced even greater amounts of porphyrins than the P. acnes strain. When treated with thiamine HCl, the amount of porphyrins present in the acne-associated bacterial strain HL053PA1 culture was definitely reduced.

4. Effect of suppressing porphyrin production in other porphyrin-producing strains (Figure 4)
Staphylococcus aureus strains were cultured and activated in BHI liquid medium and then re-inoculated at a concentration of 1/100. After treatment with thiamine HCl at a concentration of 1 w/v% and culturing for 24 hours, the strain culture was collected. 400 μl of bacterial culture was extracted with ethyl acetate and acetic acid (4:1, vol/vol). The extract was centrifuged to separate the layers, and a supernatant containing porphyrin was collected. 1.5M HCl was added to the collected supernatant to dissolve it and centrifuged to separate the layers and collect the lower layer. Fluorescence was measured at 405 nm/620 nm for the recovered soluble phase. The results are shown in FIG.

Results: When treated with thiamine HCl, the amount of porphyrin secreted by Staphylococcus aureus was definitely reduced.

5. Efficacy in inhibiting hyaluronic acid degradation (Figure 5)
Experimental method: Normal skin related type C. An experiment was conducted to confirm whether the activity of hyaluronic acid degrading enzyme secreted by P. acnes strain HL110PA3 is suppressed.

The HL110PA3 strain was cultured and activated in BHI liquid medium and then re-inoculated to the same turbidity. At this time, the cells were treated with thiamine HCl at a concentration of 1%, and the culture solution was collected after culturing for 7 days. C. In order to measure the activity of hyaluronic acid degrading enzyme secreted by C. acnes, hyaluronic acid and culture solution were mixed and reacted at 37°C for 20 minutes. After the reaction was completed, 1% sodium acetate buffer (BSA) was added to aggregate the remaining hyaluronic acid and BSA, and the absorbance at 540 nm was measured to confirm the degree of decomposition of hyaluronic acid. The results are shown in FIG.

Result: C. Since HL110PA3, a non-pathogenic strain of C. acnes, was isolated from healthy skin without inflammatory lesions, it is generally associated with healthy skin type C. acnes. Although it is classified as acne, it can break down hyaluronic acid in the skin because it secretes hyaluronic acid-degrading enzymes, as shown in experimental results. When the untreated culture solution was treated, about 85% of hyaluronic acid was degraded for 20 minutes, whereas in the culture solution of the experimental group treated with thiamine HCl, about 60% of hyaluronic acid was degraded, compared to the control (control). ), it was confirmed that the decomposition of hyaluronic acid can be suppressed by about 30% compared to the previous method.

6. Efficacy of inhibiting hyaluronic acid degradation in other strains that secrete hyaluronan degrading enzymes (Figure 6)
Experimental method: An experiment was conducted to confirm whether the activity of Staphylococcus aureus hyaluronan degrading enzyme was suppressed.

Staphylococcus aureus strains were cultured and activated in BHI liquid medium and then re-inoculated at a concentration of 1/100. After treating with thiamine HCl at a concentration of 1% and culturing for 24 hours, the strain culture solution was collected. In order to measure the activity of hyaluronic acid degrading enzyme secreted by Staphylococcus aureus, hyaluronic acid and a culture solution were mixed and reacted for 90 minutes at 37°C. In order to measure the hyaluronic acid remaining without being degraded, the remaining hyaluronic acid was quantified using a hyaluronan ELISA kit.

Results: Staphylococcus aureus, which is frequently found in atopic dermatitis lesions, can degrade hyaluronic acid. When the untreated culture solution was treated, more than 50% of hyaluronic acid was degraded, whereas in the culture solution of the experimental group treated with thiamine HCl, less than 10% of hyaluronic acid was degraded, indicating that hyaluronic acid It was confirmed that it is possible to suppress the decomposition of

7. Evaluation results of saccharide isomerate (Figure 7)
C. in the same manner as in the case of the thiamine salt. The effects of saccharide isomerate on the growth of P. acnes pathogenic and non-pathogenic strains were evaluated. The results are shown in FIG. As the saccharide isomerate, PENTAVIIN (registered trademark) product was used.

As shown in Figure 7, saccharide isomerate is also harmful to acne-inducing C. While suppressing the growth of P. acnes, the beneficial C. Since the ability to suppress the growth of P. acnes is relatively low, it was confirmed that it had a strain rebalancing effect. In addition, it was confirmed that it had the effect of inhibiting porphyrin production and hyaluronic acid degrading enzyme.

Claims (7)

A cosmetic composition for adjusting the skin microbiome, comprising as an active ingredient one or more selected from the group consisting of thiamin or a cosmetically acceptable salt thereof and saccharide isomerate. The cosmetic composition according to claim 1, wherein the cosmetic composition is for regulating Cutibacterium acnes in the skin microbiome. 3. The cosmetic composition according to claim 2, wherein the composition inhibits the growth of Cutibacterium acnes HL053PA1 strain to a greater extent than Cutibacterium acnes HL110PA3 strain. A cosmetic composition for inhibiting the production of porphyrins secreted by microorganisms, which contains as an active ingredient one or more selected from the group consisting of thiamin or its cosmetically acceptable salts and saccharide isomerates. . The cosmetic composition suppresses skin oxidative stress, improves skin inflammation, inhibits the induction of acne, increases dermal density, improves skin dryness symptoms, or improves skin tone. The cosmetic composition according to claim 3, which is used for improving. A cosmetic composition for inhibiting hyaluronic acid degrading enzyme secreted by microorganisms, which contains as an active ingredient one or more selected from the group consisting of thiamin or its cosmetically acceptable salt and saccharide isomerate. Composition. 7. The cosmetic composition according to claim 6, wherein the composition is used to improve skin elasticity, dryness, or aging symptoms by suppressing hyaluronic acid decomposition ability.