Squalane is a commonly used emollient oil-phase ingredient in skincare products. It is often associated with moisturization, emolliency, and plant-derived sourcing. However, from a chemical-structure perspective, squalane does not contain the hydrophilic groups found in humectants such as glycerol. Why, then, can it still help improve skin dryness? What changes in its properties occur when squalene is hydrogenated to squalane? And how can squalane produced from shark, olive, and bio-based routes be distinguished? This article discusses these questions.

1. From Squalene to Squalane: What Changes with Complete Hydrogenation?

1.1 Squalane Is the Saturated Derivative of Squalene

Squalene and squalane possess similar branched 30-carbon skeletons, but differ in their degree of unsaturation.

Squalene has the molecular formula C30H50 and contains six carbon–carbon double bonds. Squalane has the molecular formula C30H62 and the chemical name 2,6,10,15,19,23-hexamethyltetracosane; it is a highly branched saturated hydrocarbon.

The conversion of squalene to squalane can be represented by the following core reaction:

C30H50 + 6 H2 → C30H62

In the presence of a catalyst, each of the six C=C bonds in squalene undergoes hydrogenation and is converted into a C—C single bond. The 30-carbon skeleton of squalene is essentially retained, while the molecule is transformed from a polyunsaturated hydrocarbon into a saturated hydrocarbon. Studies on catalytic hydrogenation have demonstrated that squalene can be fully hydrogenated and converted into squalane.[3]

Squalene is an important component naturally present in human sebum. Squalane used in skincare products, by contrast, is generally obtained through the hydrogenation of squalene or other industrial synthetic routes.

1.2 Why Does Reducing Double Bonds Improve Stability?

The six C=C bonds in squalene give the molecule a high degree of unsaturation. Sites adjacent to the double bonds are susceptible to free-radical oxidation and singlet-oxygen oxidation, resulting in oxidative products such as squalene hydroperoxides.

A study by Shimizu et al. on squalene oxidation showed that singlet-oxygen oxidation and free-radical oxidation can generate different compositions of squalene monohydroperoxide isomers, indicating that the unsaturated structure of squalene is closely associated with its oxidation reactions.[2]

After complete hydrogenation, the carbon–carbon double bonds in squalane are converted into single bonds. Compared with squalene, squalane is therefore markedly less susceptible to the typical oxidation reactions of unsaturated lipids. Early cosmetic safety assessment data also noted that saturated squalane is less prone to oxidation than squalene.[8]

2. Moisturizing Mechanisms of Squalane: Emphasis on Emolliency and Moisture Retention

2.1 Skin Moisturization Involves Not Only “Adding Water” but Also “Reducing Water Loss”

The hydration status of the skin surface is closely related to the water-retention capacity of the stratum corneum.

The stratum corneum consists of corneocytes and the surrounding intercellular lipids. Experimental studies have shown that the major lipid classes in the stratum corneum lipid system include ceramides, cholesterol, and free fatty acids. These lipids form organized lamellar structures that play an important role in restricting the passage of water and other substances through the skin.[4]

Water within the skin continuously diffuses outward and evaporates into the environment. This process is commonly evaluated by transepidermal water loss (TEWL).

Accordingly, skincare ingredients can contribute to moisturization through different mechanisms:

2.2 Why Is Squalane Not a Typical Humectant?

Squalane is composed only of carbon and hydrogen and does not contain strongly hydrophilic functional groups such as hydroxyl, carboxyl, or amide groups.[1]

Therefore, unlike glycerol and other polyols, it cannot bind large amounts of water through extensive hydrogen bonding, nor does it increase the water content of the stratum corneum primarily through a pronounced humectant effect.

2.3 Squalane Mainly Provides Emollient and Supportive Moisturizing Effects

Squalane is highly hydrophobic and functions primarily as an emollient, helping improve the softness, smoothness, and oil-phase condition of the skin surface.[5]

A schematic representation of water migration is shown below:

Water in the stratum corneum → diffusion toward the skin surface → passage through the surface lipid film → evaporation into the environment

Squalane primarily improves the oil-phase condition and emollient state of the skin surface and can help maintain existing moisture.

A schematic illustration of the mechanism of action of squalane on the skin is shown below.

2.4 Squalane and Ceramides Have Different Functions

Although squalane is a lipid-soluble ingredient, it is not a major structural lipid in the physiological lipid lamellae of the stratum corneum.

The major intercellular lipids in the human stratum corneum include ceramides, cholesterol, and free fatty acids, which form highly organized lipid structures.[4]

Ceramides participate in the intercellular lipid structure of the stratum corneum; squalane primarily provides emolliency and oil-phase conditioning; and humectants such as glycerol mainly increase stratum corneum hydration.

This is also why comprehensive moisturizing formulations often contain humectants, emollients, and barrier lipids simultaneously. These three classes of ingredients act at different sites and through different mechanisms, and their combined use can create a more comprehensive moisturizing system.

3. What Are the Differences Among Animal-Derived, Olive-Derived, and Bio-Based Squalane?

3.1 Shark-Derived and Olive-Derived Routes Share a Common Approach: “Obtain Squalene First, Then Hydrogenate It”

Traditional animal-derived squalane is mainly produced using squalene from deep-sea shark liver oil as the starting material:

Shark liver oil → separation and purification of squalene → catalytic hydrogenation → squalane

Among plant-derived sources, olive oil and its processing by-products are important industrial sources of squalene:

Olive oil processing by-products → squalene enrichment → purification → catalytic hydrogenation → squalane

In their source-identification study, Camin et al. identified deep-sea shark liver oil and olive oil distillates as two important sources of squalene and squalane.[6]

A 2025 study further validated a process route in which squalene is recovered from olive pomace oil and its deodorizer distillates and subsequently converted into squalane by catalytic hydrogenation.[7]

For both routes, the chemical nature of the hydrogenation step is the same: the six double bonds in naturally occurring squalene are reduced to single bonds.

3.2 Sugarcane-Derived Squalane

Bio-based squalane can also be produced through a route combining fermentation with chemical conversion.

Publicly disclosed technical routes include:

Sugarcane-derived fermentable sugars

→ engineered microbial fermentation to produce β-farnesene

→ catalytic dimerization to form a C30 unsaturated hydrocarbon skeleton

→ hydrogenation and purification

→ bio-based squalane raw material[9,10]

The olive route primarily utilizes squalene naturally present in plants, whereas the fermentation route produces terpenoid intermediates through biomanufacturing, followed by further chemical conversion.

3.3 Source Affects the Production Pathway and Raw-Material Composition

If chemically pure 2,6,10,15,19,23-hexamethyltetracosane is being compared, then regardless of whether its carbon originally came from shark or plant sources, the target squalane molecule has the same molecular formula and chemical connectivity. Its fundamental hydrophobicity and emollient properties are still determined by its C30H62 structure.[1]

The raw-material source and manufacturing process may also affect the following:

4. If the Molecular Structure Is the Same, Why Can Stable Isotopes Still Identify the Source?

4.1 Stable Isotope Analysis Examines “Where the Carbon Came From”

Conventional chromatography and mass spectrometry mainly examine molecular composition and structure, for example, confirming whether a sample contains squalane and determining the amount of squalane present.

Stable isotope analysis focuses on another level:

What is the natural ratio of ¹³C to ¹²C in the carbon atoms that constitute these squalane molecules?

Carbon occurs in nature mainly in the form of stable isotopes such as ¹²C and ¹³C. Plant photosynthesis, biological metabolism, and food-chain processes can result in isotopic fractionation. Therefore, organic compounds formed from different biological sources may have different ¹³C/¹²C ratios.

Carbon stable isotope composition is commonly expressed as δ¹³C:

δ¹³C = [(Rsample / Rreference) − 1] × 1000‰

where:

R represents the isotope abundance ratio of ¹³C to ¹²C, i.e., R = ¹³C/¹²C; R_sample and R_reference represent the ¹³C/¹²C ratios in the sample and the reference standard, respectively.

Therefore, even if two samples ultimately contain squalane, the stable isotope composition of their carbon atoms may still differ.

4.2 Hydrogenation Changes the Double Bonds but Essentially Preserves the Original 30-Carbon Skeleton

The conversion of squalene to squalane involves hydrogenation of the double bonds:

C30H50 + 6 H2 → C30H62

The reaction adds hydrogen atoms, while the original 30-carbon skeleton is not completely broken down and reconstructed.[3]

Therefore, the carbon stable isotope characteristics carried by the squalene feedstock can be retained in the hydrogenated squalane.

4.3 Shark-Derived and Olive-Derived Squalane Show Measurable Differences in δ¹³C

In 2010, Camin et al. conducted a stable isotope study on 13 olive-derived and 15 shark-derived squalene/squalane samples.[6]

For purified squalene/squalane, the study obtained the following mean δ¹³C values:

The two groups of samples showed clear differences in their carbon isotope distributions within the sample set examined in the study.[6]

The researchers further established corresponding δ¹³C discrimination values. Under the experimental design and sample system used in the study, carbon stable isotope analysis could identify the presence of approximately 10% or more shark-derived material mixed into olive products.

The same study also measured ²H/¹H, but the hydrogen stable isotope value δ²H did not show an equally effective ability to distinguish shark-derived from olive-derived materials.[6]

4.4 Different Samples Require Different IRMS Analytical Approaches

The core instrument used for stable isotope analysis is isotope ratio mass spectrometry (IRMS).

Camin et al. proposed two analytical approaches for determining the source of squalane.[6]

For squalene or squalane with a purity above approximately 80%, the following method can be used:

Elemental Analyzer–Isotope Ratio Mass Spectrometry (EA-IRMS)

This method measures the carbon stable isotope composition of the entire sample.

For samples of lower purity, or when squalane isolated from a complex cosmetic matrix needs to be analyzed, the following method can be used:

Gas Chromatography–Combustion–Isotope Ratio Mass Spectrometry (GC-C-IRMS)

The analytical process can be summarized as follows:

Complex sample → gas chromatographic separation of squalane → combustion of the target compound to CO₂ → IRMS measurement of ¹³C/¹²C → determination of the δ¹³C value of squalane itself

This approach can reduce interference from other oils, emulsifiers, and organic substances in the formulation on the overall carbon isotope result.

4.5 Stable Isotope Source Identification Depends on Databases of Authentic-Origin Samples

The 2010 study was able to establish criteria for distinguishing shark-derived from olive-derived materials because the researchers first analyzed two groups of authentic samples with clearly defined origins and then established discrimination ranges based on the δ¹³C distributions of the two groups.[6]

Therefore, the logic of source identification is:

Samples of known origin → establish a reference δ¹³C distribution → measure an unknown sample → compare with reference data → determine whether it is consistent with the claimed source

If further differentiation among olive-derived, sugarcane-fermentation-derived, other plant-derived, or multi-source blended raw materials is required, corresponding reference samples and method-validation data need to be established separately.

5. Representative Chemicals and Research Applications Related to Squalane Structure and Moisturizing Mechanisms

Table 1. Core Compounds and Substances Related to Sources and Preparation Pathways

Table 2. Substances Related to Moisturizing Mechanisms, Stratum Corneum Lipids, and Comparative Studies

Note: The products listed above are representative Aladdin products relevant to scientific research. Specific applications should be determined according to product specifications, batch COAs, and the intended reaction or evaluation system. Additional information on product specifications, grades, and COAs can be found on the official Aladdin website by searching by “product name/CAS/catalog number.”

References

[1] National Institute of Standards and Technology. NIST Chemistry WebBook, SRD 69: Squalane, CAS 111-01-3. NIST Standard Reference Database 69.

[2] Shimizu N, Ito J, Kato S, Otoki Y, Goto M, Eitsuka T, Miyazawa T, Nakagawa K. Oxidation of squalene by singlet oxygen and free radicals results in different compositions of squalene monohydroperoxide isomers. Scientific Reports. 2018;8(1):9116. DOI: 10.1038/s41598-018-27455-5.

[3] Pandarus V, Ciriminna R, Béland F, Pagliaro M, Kaliaguine S. Solvent-Free Chemoselective Hydrogenation of Squalene to Squalane. ACS Omega. 2017;2:3989–3996. DOI: 10.1021/acsomega.7b00625.

[4] Gooris GS, Bouwstra JA. Infrared spectroscopic study of stratum corneum model membranes prepared from human ceramides, cholesterol, and fatty acids. Biophysical Journal. 2007;92(8):2785–2795. DOI: 10.1529/biophysj.106.094292.

[5] European Commission. CosIng—Cosmetic Ingredients Database: SQUALANE, CAS 111-01-3. Functions include Skin Conditioning—Emollient, Hair Conditioning, Refatting, and Skin Conditioning.

[6] Camin F, Bontempo L, Ziller L, Piangiolino C, Morchio G. Stable isotope ratios of carbon and hydrogen to distinguish olive oil from shark squalene-squalane. Rapid Communications in Mass Spectrometry. 2010;24(12):1810–1816. DOI: 10.1002/rcm.4581.

[7] Cravotto C, Bucciol F, Mazzitelli JB, Petitcolas E, Fabiano-Tixier AS, Tabasso S. From Olive Pomace to Squalane: A Green Chemistry Route Using 2-Methyltetrahydrofuran. ACS Omega. 2025;10(30):33426–33434. DOI: 10.1021/acsomega.5c03685.

[8] Elder RL, ed. Final Report on the Safety Assessment of Squalane and Squalene. Journal of the American College of Toxicology. 1982;1(2):37–56. DOI: 10.3109/10915818209013146.

[9] Fisher K, Schofer SJ, Kanne DB. Squalane and isosqualane compositions and methods for preparing the same. US Patent 8,586,814 B2. November 19, 2013.

[10] Buchanan GO, Das A, Kaur L, Motornov M, Leeson DT, Vedantham P. Sugarcane derived semi-synthetic cosmetic ingredients, methods of production thereof, and personal care products derived therefrom. WO 2024/182684 A1. September 6, 2024.

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