Multilevel Moisturizing Mechanisms of Sodium Hyaluronate and Its Derivatives: Molecular Weight Modulation, Crosslinking, Acetylation, and Major Sites of Action
Multilevel Moisturizing Mechanisms of Sodium Hyaluronate and Its Derivatives: Molecular Weight Modulation, Crosslinking, Acetylation, and Major Sites of Action
Introduction
Sodium hyaluronate, crosslinked sodium hyaluronate polymers, sodium acetylated hyaluronate, and hydrolyzed sodium hyaluronate frequently appear together in moisturizing skincare products. They all retain the repeating disaccharide backbone of hyaluronic acid, but differ in molecular chain length, mode of linkage, or substituent groups. These structural differences give rise to distinct hydration capacities, viscoelasticity, film-forming properties, skin residence characteristics, and distributions within the stratum corneum.
The core principle of a combined hyaluronic acid system is to use structural differences to perform different water-management functions:
Crosslinked networks prolong water retention, high-molecular-weight linear chains form a surface hydration film, acetylated structures modulate interactions at the skin interface, and shorter chain segments improve hydration within the stratum corneum.
The synergistic action of these ingredients is based on the principle that “structure alters molecular behavior, and molecular behavior determines the site of action.”
1 Shared Structural Features and Hydration Basis of Sodium Hyaluronate
1.1 Relationship Between Hyaluronic Acid and Sodium Hyaluronate
Hyaluronic acid, abbreviated as HA, is a linear, non-sulfated glycosaminoglycan composed of repeating disaccharide units of D-glucuronic acid and N-acetyl-D-glucosamine. The sugar units are linked by alternating β-1,3 and β-1,4 glycosidic bonds [1].
Sodium hyaluronate is the sodium salt form of hyaluronic acid. The two share the same polysaccharide backbone and differ mainly in the protonation or salt state of the carboxyl groups on the glucuronic acid residues and in the form of the counterion.
The carboxyl groups in hyaluronic acid can dissociate:
HA—COOH ⇌ HA—COO⁻ + H⁺
After sodium hyaluronate is formed, sodium ions serve as counterions for the carboxylate groups:
HA—COO⁻ · Na⁺
In aqueous environments close to neutral pH, the carboxyl groups of hyaluronic acid exist predominantly in the carboxylate form. Sodium hyaluronate has good water dispersibility and formulation compatibility and is therefore a commonly used form of hyaluronic acid in skincare products.
The relationships among sodium hyaluronate and its major structural derivatives are shown below.
Ingredient | Main Structural Characteristics | Core Structural Change |
Sodium hyaluronate | Non-crosslinked linear polysaccharide sodium salt | Retains intact, long linear chains |
Crosslinked sodium hyaluronate polymer | Multiple hyaluronic acid chains connected to one another | Conversion from linear chains into a three-dimensional network |
Sodium acetylated hyaluronate | Acetyl groups introduced onto some hydroxyl groups | Alters the polarity distribution on the molecular surface |
Hydrolyzed sodium hyaluronate | Long chains cleaved into shorter chain segments | Reduces the degree of polymerization and molecular weight |
1.2 Why Sodium Hyaluronate Can Bind Water
The molecular chains of sodium hyaluronate contain numerous carboxylate, hydroxyl, and amide groups. These polar groups interact with water molecules through ion–dipole interactions and hydrogen bonding, forming hydration layers around the polymer chains.
This process can be represented in simplified form as:
HA—COO⁻ + nH₂O ⇌ HA—COO⁻·(H₂O)ₙ
Carboxylate groups carry negative charges, and electrostatic repulsion between neighboring charges gives hyaluronic acid chains a relatively large spatial dimension in water. As molecular weight increases, the chains gradually overlap and become entangled, increasing solution viscosity, viscoelasticity, and film-forming ability [2].
The moisturizing action of sodium hyaluronate mainly involves three consecutive processes:
1. Polar groups bind and organize surrounding water molecules;
2. Hydrated polymers slow the migration of water through the film layer;
3. Long-chain entanglement or crosslinked networks prolong the residence of water on the skin surface.
The role of sodium hyaluronate is to regulate the binding state, spatial distribution, and migration rate of water already present in the system.
2 How Molecular Weight Determines the Site of Action of Sodium Hyaluronate
2.1 Molecular Weight Alters Chain Size and Molecular Motion
The molecular weight of sodium hyaluronate depends on the number of repeating disaccharide units in the molecular chain. As molecular weight increases, the chain becomes longer, its hydrodynamic size increases, and chain overlap and entanglement become stronger. As molecular weight decreases, the chain segments become shorter, viscosity decreases, and diffusion becomes faster.
The principal performance differences associated with molecular weight are shown below.
Change in Molecular Weight | Properties Mainly Enhanced | Properties Relatively Reduced |
Increased molecular weight | Viscosity, viscoelasticity, film formation, and surface residence | Diffusion within the stratum corneum |
Decreased molecular weight | Fluidity, diffusion rate, and distribution within the stratum corneum | Interchain entanglement and film continuity |
Further shortening of chain segments | Potential for interaction with keratinocytes | Ability to form a high-molecular-weight hydration film |
2.2 High-Molecular-Weight Sodium Hyaluronate Forms a Surface Hydration Film
High-molecular-weight sodium hyaluronate forms large hydrated coils in water and produces a viscoelastic system through interchain entanglement. After application, as part of the water evaporates, the long chains form a continuous hydrophilic film on the surface of the stratum corneum.
Raman microscopic imaging showed that, under the conditions of the ex vivo skin study, hyaluronic acid with a molecular weight of 1,000–1,400 kDa remained mainly in the outer layers of the skin, whereas hyaluronic acid in the ranges of 20–50 kDa and 100–300 kDa showed more pronounced distribution within the stratum corneum [3]. These findings suggest that, compared with lower-molecular-weight samples, high-molecular-weight hyaluronic acid tends to remain on the skin surface and in the outer stratum corneum. Its advantage lies in hydration and film formation rather than penetration into the dermis to replenish the extracellular matrix.
2.3 Hydrolyzed Sodium Hyaluronate Enhances Diffusion Within the Stratum Corneum
Hydrolyzed sodium hyaluronate is produced by cleaving some glycosidic bonds through enzymatic hydrolysis, acid hydrolysis, or other controlled degradation processes, converting long chains into shorter chain segments. Hydrolysis is one method of obtaining shorter-chain hyaluronic acid, but “hydrolyzed sodium hyaluronate” and “low-molecular-weight hyaluronic acid” are not completely synonymous. The actual behavior of the ingredient still depends on its average molecular weight and molecular weight distribution.
The process can be represented in simplified form as:
Long-chain sodium hyaluronate
——enzymatic hydrolysis, acid-catalyzed hydrolysis, or other controlled degradation→ Shorter sodium hyaluronate chain segments
The following changes generally occur after hydrolysis:
① The average molecular weight decreases;
② The hydrodynamic size decreases;
③ Interchain entanglement is reduced;
④ Solution viscosity decreases;
⑤ Diffusion capacity increases;
⑥ The ability to form a continuous surface film decreases.
Under specific research and formulation conditions, shorter chain segments may show more pronounced distribution within the stratum corneum and may interact with water through carboxylate, hydroxyl, and amide groups. They therefore have the potential to improve water distribution within the stratum corneum.
The actual distribution of sodium hyaluronate in the skin is influenced not only by average molecular weight, but also by molecular weight distribution, ingredient concentration, formulation vehicle, application time, stratum corneum water content, and skin-barrier condition.
3 Crosslinked Sodium Hyaluronate Polymers: From Linear Long Chains to a Three-Dimensional Hydration Network
3.1 Crosslinking Alters the Mode of Molecular Connection
Linear sodium hyaluronate consists of long chains that are independent of or entangled with one another. Crosslinking creates connection points between different molecular chains, converting linear chains into a three-dimensional polymer network.
After crosslinking, the free movement of the hyaluronic acid chains is restricted. The network can absorb water and swell, but it does not diffuse rapidly through the aqueous phase in the same manner as linear molecules.
The actual properties of a crosslinked material depend on several structural parameters: the crosslinking agent and type of crosslinking bond; crosslink density; network particle size; equilibrium water uptake; swelling rate; and the proportion of soluble linear hyaluronic acid.
Therefore, even when different crosslinked sodium hyaluronate polymers share the same ingredient name, they may exhibit different water absorption, viscoelasticity, and skin residence properties.
3.2 How a Three-Dimensional Network Prolongs Water Residence
After water enters the crosslinked network, it fills the internal spaces and causes the polymer to swell. Crosslinking points prevent the chains from separating completely, allowing the hydrated structure to be maintained for a longer period.
The principal differences between crosslinked sodium hyaluronate and high-molecular-weight linear sodium hyaluronate are shown below.
Property | High-Molecular-Weight Sodium Hyaluronate | Crosslinked Sodium Hyaluronate Polymer |
Molecular structure | Linear long chains with interchain entanglement | Covalently connected three-dimensional network |
Mode of hydration | Forms hydrated coils and a continuous film layer | Absorbs water into the network and swells |
Molecular migration | Can move to some extent with the aqueous phase | The network as a whole migrates more slowly |
Main function | Surface film formation and immediate skin softness | Sustained water storage and prolonged residence |
Main location | Skin surface and outer stratum corneum | Formulation film layer, skin surface, and outermost stratum corneum |
In a human skin explant study, after daily treatment with a specific crosslinked resilient hyaluronic acid formulation, epidermal water content was 7.6% higher than that of the control on Day 9. On Day 2, transepidermal water loss was 27.8% lower than that of the control, while the high-molecular-weight linear hyaluronic acid group showed a 15.6% reduction [4].
These results reflect the effects of the specific crosslinked material on epidermal water distribution and barrier-related parameters. The main site of action of an intact crosslinked network remains in the outer layers of the skin, and its hydration effect does not require penetration into the viable epidermis or dermis.
4 Sodium Acetylated Hyaluronate: Modulation of Hydration Capacity and Skin-Interface Interactions
4.1 Acetylation Alters the Polarity Distribution on the Molecular Surface
Sodium acetylated hyaluronate is produced by introducing acetyl groups onto some of the hydroxyl groups of the sodium hyaluronate backbone.
The structural change can be represented in simplified form as:
HA—OH → HA—O—COCH₃
After acetylation, the carboxylate groups, amide groups, and unsubstituted hydroxyl groups of the hyaluronic acid backbone can still interact with water. The newly introduced acetyl groups alter the polarity distribution and spatial interactions of the molecular surface.
4.2 Molecular Weight and Degree of Acetylation Jointly Determine Performance
The effects of sodium acetylated hyaluronate are jointly determined by two principal parameters:
1. Molecular weight: affects chain size, diffusion capacity, and film-forming ability;
2. Degree of acetylation: affects polarity distribution, mode of hydration, and resistance to hyaluronidase degradation.
At a low degree of acetylation, the overall behavior of the molecule may remain similar to that of unmodified sodium hyaluronate. As the degree of acetylation increases, interactions between the molecule and the skin–water interface change accordingly. An excessively high degree of substitution may also affect the original water solubility and hydration characteristics.
One study compared fully acetylated sodium hyaluronate and non-acetylated sodium hyaluronate, both with a molecular weight of 15 kDa. Raman analysis showed that acetylation affected the distribution of the material in ex vivo skin. Hyaluronidase assays showed that the acetylated material had greater resistance to enzymatic degradation. Improvements in matrix metalloproteinase-related parameters and the appearance of wrinkles were also observed in cellular studies, skin explant studies, and human use tests [5].
These results were obtained using ingredients with specific molecular weights and degrees of acetylation and cannot be directly extrapolated to all sodium acetylated hyaluronate products. Current evidence supports that acetylation can alter the distribution of this material in ex vivo skin and improve its resistance to hyaluronidase degradation.
5 Low-Molecular-Weight Hyaluronic Acid and the Endogenous Moisturizing System of the Stratum Corneum
5.1 Direct Hydration and Natural Moisturizing Factor
After shorter hyaluronic acid chains enter the stratum corneum, they can bind water directly. This represents physical hydration produced by the polar groups of hyaluronic acid itself.
Corneocytes also contain natural moisturizing factor, or NMF, which mainly consists of free amino acids, pyrrolidone carboxylic acid, urocanic acid, and other hygroscopic small molecules. NMF is located within corneocytes and helps maintain the water content and flexibility of the stratum corneum.
One important source of NMF is the degradation of filaggrin.
The formation process can be summarized as:
Profilaggrin → Filaggrin → Proteolytic products → Free amino acids and their derivatives → NMF
5.2 Effects of Specific Low-Molecular-Weight Hyaluronic Acid on Filaggrin Metabolism and Natural Moisturizing Factor Formation
A three-dimensional reconstructed human epidermis study evaluated a specific low-molecular-weight hyaluronic acid of less than 10 kDa. The study showed that the material increased parameters related to profilaggrin, involucrin, caspase-14, and bleomycin hydrolase [6]. Caspase-14 and bleomycin hydrolase participate in the subsequent degradation of filaggrin, and filaggrin degradation products are an important source of NMF.
The study indicates that, in addition to directly binding water, the specific low-molecular-weight hyaluronic acid may also affect keratinocyte differentiation and processes related to filaggrin metabolism and natural moisturizing factor formation.
It should be noted that the biological effects of low-molecular-weight hyaluronic acid depend on molecular weight, concentration, and the experimental model. The results obtained with the specific material described above cannot be directly extrapolated to all low-molecular-weight or oligomeric hyaluronic acid products [7,8].
6 Major Distribution Patterns and Functional Tendencies of Different Hyaluronic Acid Ingredients
Sodium hyaluronate and its derivatives can perform different functions from the outermost layers inward according to their principal sites of action.
Main Site of Action | Main Ingredient | Molecular Behavior | Main Function |
Formulation film layer and skin surface | Crosslinked sodium hyaluronate polymer | Three-dimensional network absorbs water and swells, with relatively slow overall migration | Establishes a sustained hydration layer and prolongs water residence |
Skin surface and outer stratum corneum | High-molecular-weight sodium hyaluronate | Long chains hydrate, become entangled, and form a continuous film | Provides immediate hydration, softens the skin, and improves the appearance of dry lines |
Skin surface–stratum corneum interface, with the specific distribution depending on molecular weight, degree of acetylation, and formulation conditions | Sodium acetylated hyaluronate | Changes in surface polarity distribution and resistance to enzymatic degradation | Maintains hydration and improves the resistance of specific materials to hyaluronidase degradation |
Within the stratum corneum | Hydrolyzed sodium hyaluronate | Shorter chain segments diffuse and bind water | Improves water distribution within the stratum corneum |
Lower stratum corneum or superficial viable epidermis | Specific low-molecular-weight hyaluronic acid | May interact with keratinocytes | May support epidermal differentiation and processes related to FLG and NMF |
These sites of action are not completely separate and may overlap to some extent. The actual distribution of each ingredient is also affected by molecular weight, crosslinking status, degree of acetylation, use concentration, and formulation vehicle.
The multilevel, complementary moisturizing mechanisms of sodium hyaluronate and its derivatives are illustrated below. The figure primarily presents the distribution tendencies and functional roles of different ingredients. It does not indicate that the ingredients are sequentially converted into one another, nor does it imply absolute boundaries between their sites of action.
7 How Combined Hyaluronic Acid Systems Produce Multilevel, Complementary Moisturization
7.1 Crosslinked Networks Establish an Outer Water-Storage Region
After the product is applied, the crosslinked sodium hyaluronate polymer absorbs water from the formulation and swells. The three-dimensional network restricts the rapid migration of polymer chains and water, creating a hydrated region with a relatively long residence time on the skin surface.
This structure mainly addresses how water can be retained for a longer period in the outer layers of the skin.
7.2 High-Molecular-Weight Sodium Hyaluronate Forms a Continuous Hydration Film
High-molecular-weight sodium hyaluronate expands in the aqueous phase and undergoes interchain entanglement. As water gradually decreases, the linear long chains form a soft, continuous hydrophilic film on the surface of the stratum corneum.
The crosslinked network primarily contributes to water storage, whereas the high-molecular-weight linear chains primarily contribute to spreading and film formation. Together, these structures improve the uniformity and persistence of water coverage.
7.3 Sodium Acetylated Hyaluronate Enhances Interfacial Residence
By altering the polarity distribution of the molecular surface, sodium acetylated hyaluronate can affect its mode of hydration, resistance to enzymatic degradation, and distribution in skin models. Research on a specific 15 kDa material showed that acetylation altered its distribution in ex vivo skin and increased its resistance to hyaluronidase degradation. Actual performance still depends on molecular weight, degree of acetylation, and formulation conditions.
7.4 Hydrolyzed Sodium Hyaluronate Improves Hydration Within the Stratum Corneum
The shorter chain segments in hydrolyzed sodium hyaluronate have relatively high diffusion capacity. Under specific research and formulation conditions, they may show more pronounced distribution within the stratum corneum and interact with water in the corresponding regions.
Some low-molecular-weight hyaluronic acid materials with clearly defined molecular weights and supporting experimental data may also affect keratinocyte differentiation and processes related to FLG and NMF.
8 Combined Hyaluronic Acid Systems and Skin-Barrier Moisturization
Sodium hyaluronate and its derivatives mainly contribute to water binding, storage, residence, and distribution within the stratum corneum. The ability of the skin to retain water over the long term is also influenced by the structure of intercellular lipids in the stratum corneum.
Combined hyaluronic acid systems and barrier lipids perform different functions:
System | Main Function |
Sodium hyaluronate and its derivatives | Bind water, form a hydration film, prolong residence, and improve water distribution within the stratum corneum |
Small-molecule humectants such as glycerol and amino acids | Bind water within the stratum corneum and the aqueous phase of the formulation |
Oils, esters, and fatty alcohols | Improve skin softness and surface lubrication |
Ceramides, cholesterol, and free fatty acids | Support the structure of intercellular lipids in the stratum corneum |
Occlusive film-forming ingredients | Slow the outward diffusion of water into the environment |
Combined hyaluronic acid systems can improve skin hydration but cannot replace the lipids of the stratum corneum. A rational formulation should coordinate humectancy, hydration, emolliency, and reduction of water loss, while avoiding film contraction, tackiness, or tightness caused by high concentrations of hydrophilic polymers under low-humidity conditions.
9 Classification and Research Applications of Chemicals Related to Sodium Hyaluronate and Its Derivatives
Table 1 Core Hyaluronic Acid Ingredients, Salt Forms, and Molecular-Weight Series
Classification | CAS No. | Aladdin Cat. No. | Name | Specification or Purity | Product Features and Applications |
Hyaluronic acid parent compound | 9004-61-9 | Hyaluronic Acid | Moligand™, from rooster comb | Used for studies of the repeating disaccharide backbone of hyaluronic acid, carboxyl-group dissociation, conversion between acid and salt forms, molecular-chain hydration, and viscoelastic properties. | |
Potassium hyaluronate salt control | 31799-91-4 | Potassium Hyaluronate (HA-K) | From rooster comb | Used to compare the solubility, hydration state, ionic-strength response, and rheological properties of hyaluronic acid with different counterions. | |
General-purpose sodium hyaluronate ingredient | 9067-32-7 | Sodium Hyaluronate, from Streptococcus equi | ≥95% | Used for studies of sodium hyaluronate hydration, viscosity, chain conformation, surface film formation, and materials derived from microbial fermentation. | |
Medium-to-low-molecular-weight sodium hyaluronate | 9067-32-7 | Low-Molecular-Weight Sodium Hyaluronate (HA-TLM 20-40) | Molecular weight: 200–400 kDa | Used for studies of stratum corneum distribution, hydration capacity, diffusion behavior, and compatibility with high-molecular-weight ingredients. | |
High-molecular-weight sodium hyaluronate | 9067-32-7 | Sodium Hyaluronate | Molecular weight: 600,000–1,200,000 | Used for studies of long-chain hydration, interchain entanglement, solution viscoelasticity, film formation on the skin surface, and immediate moisturization. | |
Ultra-high-molecular-weight sodium hyaluronate | 9067-32-7 | Sodium Hyaluronate | Molecular weight: 1,900,000–3,900,000 | Used for studies of ultra-long-chain entanglement, viscosity development, surface hydration-film stability, and regulation of water migration. | |
Ultra-high-molecular-weight sodium hyaluronate | 9067-32-7 | High-Molecular-Weight Sodium Hyaluronate (HA-THM) | Molecular weight: ≥1.8 MDa | Used for studies of high-molecular-weight sodium hyaluronate film formation, surface residence, viscoelastic networks, and hydration of the outer stratum corneum. | |
Medium-to-low-molecular-weight sodium hyaluronate | 9067-32-7 | Sodium Hyaluronate | ≥95%, molecular weight: 50,000–70,000 | Used for studies of molecular-weight gradients, stratum corneum diffusion, internal hydration, and synergistic formulation with long-chain sodium hyaluronate. | |
Low-molecular-weight sodium hyaluronate | 9067-32-7 | Sodium Hyaluronate | ≥95%, molecular weight: 30,000–50,000 | Used for studies of the diffusion rate, stratum corneum distribution, hydration state, and chain-length effects of low-molecular-weight sodium hyaluronate. | |
Low-molecular-weight sodium hyaluronate | 9067-32-7 | Sodium Hyaluronate | ≥95%, molecular weight: 15,000–30,000 | Used for studies of the distribution of shorter hyaluronic acid chains within the stratum corneum, direct hydration, and molecular-weight-dependent effects. | |
Ultra-low-molecular-weight sodium hyaluronate | 9067-32-7 | Sodium Hyaluronate | ≥95% (HPLC), molecular weight: 7,000–12,000 | Used for studies of stratum corneum diffusion, epidermal-model responses, and filaggrin-related mechanisms involving ultra-low-molecular-weight sodium hyaluronate. | |
Enzymatically cleaved oligomeric sodium hyaluronate | 9067-32-7 | Enzymatically Cleaved Oligomeric Sodium Hyaluronate | Molecular weight: <10 kDa | Used for studies of the molecular-weight distribution, diffusion within the stratum corneum, cellular responses, and natural moisturizing factor-related processes of enzymatically cleaved oligomeric chains. | |
Ultra-low-molecular-weight sodium hyaluronate | 9067-32-7 | Ultra-Active Hyaluronic Acid | Molecular weight: <5 kDa | Used for studies of the diffusion behavior of hyaluronic acid oligomers, keratinocyte responses, epidermal differentiation, and filaggrin metabolism. |
Table 2 Reagents for Studies of Hyaluronic Acid Structural Composition, Crosslinking Modification, Acetylation, and Degradation
Classification | CAS No. | Aladdin Cat. No. | Name | Specification or Purity | Product Features and Applications |
Uronic acid control for the repeating unit | 6556-12-3 | D-Glucuronic Acid | Moligand™, ≥98% | Used for studies of the repeating disaccharide composition, carboxyl structure, monosaccharide composition analysis, and identification of hydrolysis products of hyaluronic acid. | |
Amino sugar control for the repeating unit | 7512-17-6 | N-Acetyl-D-Glucosamine | ≥98% | Used for analysis of the repeating disaccharide composition, acetamido structure, hydrolysis products, and monosaccharide quantification of hyaluronic acid. | |
Amino sugar structural control | 66-84-2 | D-(+)-Glucosamine Hydrochloride | ≥99% | Used as a deacetylated structural control for N-acetyl-D-glucosamine and for studies of amino sugar analysis and degradation products. | |
Uronic acid lactone control | 32449-92-6 | D-Glucuronic Acid Lactone | ≥99% | Used for studies of glucuronic acid lactonization, structural transformation under acidic conditions, and analysis of hyaluronic acid degradation products. | |
Hyaluronidase digestion reagent | 9001-54-1 | Hyaluronidase from Bovine Testes | EnzymoPure™, ≥400 U/mg | Used for enzymatic degradation of hyaluronic acid, molecular-weight reduction, degradation-kinetics studies, and evaluation of the resistance of crosslinked or acetylated materials to enzymatic degradation. | |
Epoxy-type crosslinking agent | 2425-79-8 | 1,4-Butanediol Diglycidyl Ether (BDDE) | ≥95% | Used for hydroxyl-group crosslinking of hyaluronic acid, hydrogel-network construction, and studies of crosslink density, water absorption, swelling, and viscoelastic properties. | |
Hydrazide-type crosslinking agent | 1071-93-8 | Adipic Acid Dihydrazide (ADH) | ≥99% (HPLC) | Used for hydrazide functionalization of hyaluronic acid carboxyl groups, carbodiimide-mediated crosslinking, hydrogel construction, and network-stability studies. | |
Carboxyl-activating coupling reagent | 25952-53-8 | 1-Ethyl-3-(3-Dimethylaminopropyl)carbodiimide Hydrochloride | ≥98% | Used for activation of hyaluronic acid carboxyl groups, amide-bond formation, hydrazide crosslinking, and functional-group grafting studies. | |
Carboxyl-activation additive | 6066-82-6 | N-Hydroxysuccinimide (NHS) | ≥98% | Used to stabilize activated intermediates of hyaluronic acid carboxyl groups, improve amidation efficiency, and investigate crosslinking conditions. | |
Acetylation reagent | 108-24-7 | A1506320 | Acetic Anhydride (Regulated Precursor Chemical) | European Pharmacopoeia (Ph. Eur.), puriss. p.a., ISO, ACS, ≥99% (GC) | Used for hydroxyl-group acetylation of hyaluronic acid, regulation of the degree of acetyl substitution, and preparation of acetylated hyaluronic acid structures. |
Acetylation reaction medium | 64-19-7 | Glacial Acetic Acid | Guaranteed reagent, ≥99.5% | Used as a reaction medium for hyaluronic acid acetylation, for adjustment of acidic conditions, and for control of the degree of acetylation. | |
Alkaline reaction and neutralization reagent | 1310-73-2 | Sodium Hydroxide | Guaranteed reagent, ≥96% | Used for formation of the sodium salt of hyaluronic acid, ionization of carboxyl groups, establishment of alkaline crosslinking conditions, and post-reaction neutralization. | |
Ionic-strength adjustment reagent | 7647-14-5 | Sodium Chloride | Anhydrous grade, reagent grade, high purity, ≥99% | Used for studies of hyaluronic acid polyelectrolyte-chain conformation, ionic screening, hydration layers, solution viscosity, and osmotic pressure. | |
Acid-hydrolysis and acidity-adjustment reagent | 7647-01-0 | H475775 | Hydrogen Chloride (Regulated Precursor Chemical) | Reagent grade, high purity, ≥99% | Used for acid hydrolysis of hyaluronic acid, molecular-weight regulation, glycosidic-bond stability studies, and adjustment of reaction-system acidity. |
Table 3 Control Products for Studies of Natural Moisturizing Factor, Stratum Corneum Hydration, and Barrier Lipids
Classification | CAS No. | Aladdin Cat. No. | Name | Specification or Purity | Product Features and Applications |
Core natural moisturizing factor component | 28874-51-3 | Sodium L-Pyrrolidone-5-Carboxylate | 50% oily liquid | Used for studies of natural moisturizing factor composition, hygroscopicity within corneocytes, synergy between hyaluronic acid and small-molecule moisturizers, and comparison of hydration capacity. | |
Acid-form natural moisturizing factor control | 98-79-3 | L-Pyroglutamic Acid | UltraBio™, ultrapure grade | Used for studies of the acid-form structure of pyrrolidone carboxylic acid, acid–base balance of natural moisturizing factor, and moisturizing mechanisms in the stratum corneum. | |
Filaggrin-degradation amino acid control | 56-45-1 | L-Serine | Animal-origin-free, USP, Moligand™, European Pharmacopoeia (Ph. Eur.), ≥98.5% | Used for studies of filaggrin degradation products, the amino acid composition of natural moisturizing factor, and stratum corneum hydration. | |
Filaggrin-degradation amino acid control | 56-41-7 | L-Alanine | UltraBio™, ultrapure grade, ≥99.5% (NT) | Used for studies of free amino acid composition in the stratum corneum, natural moisturizing factor quantification, and mechanisms of action of low-molecular-weight hyaluronic acid. | |
Filaggrin-degradation amino acid control | 71-00-1 | L-Histidine | UltraBio™, ≥99.5% (NT) | Used for studies of filaggrin degradation, histidine metabolism, urocanic acid formation, and natural moisturizing factor in the stratum corneum. | |
Filaggrin-degradation amino acid control | 74-79-3 | L-Arginine | Moligand™, ≥99% (HPLC) | Used for studies of free amino acid composition in the stratum corneum, acid–base buffering, natural moisturizing factor, and hydration state. | |
Histidine metabolite control | 104-98-3 | 4-Imidazoleacrylic Acid | ≥98% | Used for studies of urocanic acid structure, histidine metabolism, natural moisturizing factor composition, and the acidic environment of the stratum corneum. | |
Small-molecule humectant control | 56-81-5 | Glycerol | Anhydrous grade, UltraBio™, molecular biology grade, ≥99.5% (GC) | Used for studies of small-molecule humectancy, stratum corneum hydration, persistence of moisturization, and compatibility with sodium hyaluronate of different molecular weights. | |
Natural moisturizing factor and keratin-hydration control | 57-13-6 | Urea | Crystalline, pharmaceutical grade, Ph. Eur., BP, ChP, JP, USP | Used for studies of natural moisturizing factor composition, keratin hydration, stratum corneum softness, and combined hyaluronic acid moisturizing systems. | |
Stratum corneum barrier-lipid control | 57-88-5 | C432975 | Cholesterol, from Lanolin | PharmPure™, JP, BP, European Pharmacopoeia (Ph. Eur.), NF, ultrapure grade | Used for studies of intercellular lipid models of the stratum corneum, barrier structure, transepidermal water loss, and compatibility with hyaluronic acid hydration systems. |
Essential fatty acid and barrier-lipid control | 60-33-3 | Linoleic Acid | Moligand™, ≥99% (GC) | Used for studies of free fatty acid composition, stratum corneum lipid organization, barrier function, and synergistic mechanisms between hydration and lipids. |
Note: The crosslinking, coupling, acetylation, and hydrolysis reagents listed above are primarily intended for laboratory preparation and mechanistic research and are not equivalent to finished ingredients that can be directly incorporated into cosmetic formulations. Additional product specifications, grades, and certificate of analysis information can be retrieved from the Aladdin website by searching the product name, CAS number, or catalog number.
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