What Are Unsaponifiables in Botanical Oils — And Why They Matter in Formulation

Every botanical oil is more than a fat. The fatty acid profile gets most of the attention — and rightly so. It determines penetration, oxidative stability, and skin compatibility. But there is a second layer: the unsaponifiables in botanical oils.

The unsaponifiable fraction is the portion of an oil that does not convert to soap during saponification. Small — typically 0.5–2% of total oil mass, occasionally higher. What it contains is what gives each oil its distinct character: the slip of olive oil, the orange pigment of sea buckthorn, the antioxidant depth of argan.

Over 70 vegetable oils have been characterized by their lipid composition and biological activity in topical applications. [PMID 32547393] The pattern that emerges: the unsaponifiable fraction modulates oil stability, skin feel, and anti-inflammatory activity — working alongside the fatty acid base, not independently of it.

This post maps the unsaponifiable fraction systematically — what it contains, what each class does, and how to use it in formulation. For the fatty acid side of the same equation, start with fatty acids profile in skincare and explore further the importance of unsaponifiables in botanical oils.

Phenols and Polyphenols — The Antioxidant & Anti-Inflammatory Backbone

Phenols and polyphenols are secondary plant metabolites — compounds the plant produces not for energy, but for protection. In botanical oils, they concentrate in the unsaponifiable fraction. Even in trace amounts, they contribute meaningfully to oxidative stability and anti-inflammatory activity. Phenols and polyphenols sit in the unsaponifiable fraction and give many oils their antioxidant strength. Even in trace amounts, these compounds contribute meaningfully to oxidative stability and anti-inflammatory activity.

Phenylpropanoids

Ferulic acid and caffeic acid are hydroxycinnamic acids — plant-derived antioxidants that neutralize free radicals and slow lipid oxidation. They appear in argan, sesame, rice bran, and olive oil, and their presence correlates directly with those oils’ known oxidative stability — a chemistry fact, not a marketing claim.

Flavonoids

Flavonoids are polyphenolic compounds with documented antioxidant and anti-inflammatory activity. In botanical oils, they appear in camellia, olive, and grapeseed — contributing to the lightweight, soothing character of these oils in leave-on applications and supporting the barrier-calming effects documented for several of them in topical use. [PMID 29280987]

Tannins

Tannins are plant-derived polyphenols that bind proteins and create a characteristic astringent effect. In oils, they produce the dry-touch finish characteristic of hazelnut, camellia, and pomegranate seed oil — useful in formulation for balancing richer oils and reducing greasiness in a blend.

Terpenes, squalene & Terpenoids

Triterpenes

Triterpenes are a class of naturally occurring compounds built from five-carbon isoprene units — structurally complex molecules that appear consistently in the unsaponifiable fraction of botanical oils and plant waxes. Lupeol and α-amyrin — identified alongside squalene and C18–C34 n-alkanes in the unsaponifiable fractions of seed oils [PMID 10691620] — show anti-inflammatory activity and contribute to barrier support.

Shea butter is the most accessible triterpene source in cosmetic formulation. Its barrier-repair and anti-inflammatory reputation is largely carried by the triterpene fraction — not the fatty acids.

Squalene

Squalene is a triterpene hydrocarbon — one of the most abundant compounds in the unsaponifiable fraction of olive oil, where it can represent up to 50% of the fraction. It occurs naturally in human sebum, which explains its excellent skin compatibility and the characteristic slip it contributes to olive oil in formulation.

Squalane is the stabilized, hydrogenated form. The double bonds that make squalene prone to oxidation are removed — the result is a shelf-stable ingredient with the same sensory properties and none of the rancidity risk. In formulation, squalane is the more practical choice for standalone use; squalene is best utilized as part of the intact unsaponifiable fraction in cold-pressed oils.

Tetraterpenoids (Carotenoids)

Carotenoids are fat-soluble pigments synthesized by plants as photoprotective compounds. In botanical oils, they concentrate in the unsaponifiable fraction and are responsible for the intense orange and yellow pigments in sea buckthorn and marigold oil. Heat-sensitive — they degrade rapidly with processing. Cold-pressed versions retain both the colour and the antioxidant activity that refined versions lose.

If you love colourful, carotenoid-rich skincare ingredients, you can explore my Annatto Oil for Glowing Skin guide for a practical example.

Phytosterols — Skin Barrier Support

Phytosterols are plant-derived sterols — structurally similar to cholesterol, the skin’s own barrier lipid. That structural similarity allows them to integrate into the lipid matrix of the stratum corneum more effectively than purely exogenous compounds, which is why phytosterol-rich oils consistently show up in barrier-repair formulations.

Key Sterols

β-sitosterol, campesterol, and stigmasterol are the dominant phytosterols across most botanical oils. β-sitosterol is typically the most abundant. Concentration varies significantly by oil type — rice bran, corn, and rapeseed show higher phytosterol content than most other vegetable oils. [PMID 31404986] In the Cucurbitaceae family — watermelon, cucumber — Δ7-sterols dominate. In other seed oils, Δ5-sterols appear at highest concentrations. [PMID 10691620]

If you enjoy working with nourishing blends and want a practical example of sterol-rich formulations, take a look at my Nourishing Facial Oil guide.

Unsaponifiable Content — Selected Oils

Topical plant oils with documented anti-inflammatory and antioxidant properties — including phytosterol-rich oils — show consistent benefits for skin barrier repair across the evidence base. [PMID 29280987]

Vitamin E — Tocopherols and Tocotrienols

Tocopherols (α, β, γ, δ)

Tocopherols are the primary fat-soluble antioxidants in botanical oils — a family of four isomers (α, β, γ, δ) that differ in biological activity and distribution across plant species. They scavenge free radicals, slow oxidative degradation, and extend shelf life — particularly critical in linoleic acid-rich oils prone to rancidity.

α-tocopherol has the highest biological activity in skin. γ-tocopherol is the most common form in seed oils. The distinction matters in formulation — synthetic dl-α-tocopherol is a racemic mixture and is not interchangeable with the mixed tocopherol fraction that cold-pressing preserves intact.

Tocotrienols

Tocotrienols are the lesser-known members of the vitamin E family — structurally similar to tocopherols but with an unsaturated side chain that gives them different tissue distribution and potentially stronger antioxidant activity in some biological systems. They appear primarily in rice bran and palm oils. The research base is considerably thinner than for tocopherols.

Synthetic vs. Natural Vitamin E

Not all vitamin E is equal — and the difference matters in formulation. Synthetic vitamin E (dl-α-tocopherol) is produced from petrochemical precursors and exists as a racemic mixture of eight stereoisomers. Natural vitamin E (d-α-tocopherol) is a single enantiomer extracted from plant sources — with higher biological activity and better tissue retention.

In cold-pressed oils, tocopherols exist as part of the intact unsaponifiable fraction — not added separately. Refining removes a significant portion of this fraction. That is one of the formulation arguments for choosing unrefined over refined — the tocopherol protection is already built in..

How Unsaponifiables Influence Oil Performance

Antioxidant Power and Oil Stability

Tocopherols are the primary defense against oxidative rancidity in botanical oils — but their concentration depends directly on how the oil was processed. Cold-pressed oils retain the full tocopherol fraction. Solvent extraction and refining degrade it through heat, chemical exposure, and deodorization. The practical consequence: a refined oil with a similar fatty acid profile will have a shorter shelf life and less inherent oxidative protection than its cold-pressed equivalent. That gap matters in formulation, especially for high-PUFA oils where rancidity is already a risk..

Sensory Feel and Colour

The unsaponifiable fraction is what makes botanical oils visually and texturally distinct — and those sensory signals carry formulation information. Carotenoids produce the orange and yellow pigments in sea buckthorn and marigold — their intensity tells you how much of the fraction survived processing. Tannins create the dry-touch, astringent finish in hazelnut and pomegranate seed oil. Squalene gives olive oil its characteristic slip. Before an oil reaches skin, these signals already tell you how it will behave in a blend.

Skin Benefits — What the Evidence Actually Shows

The research on unsaponifiables is more specific — and more honest — than most skincare content suggests.

A 2025 in vitro study (PMID: 40707519) tested vegetable oils, fatty acids, and unsaponifiables on human keratinocytes and fibroblasts. Cell proliferation was driven primarily by linoleic acid – unsaponifiables showed no significant effect on proliferation or wound closure.

This does not mean unsaponifiables are inert. It means the evidence for direct cell-level activity in skin repair is thinner than commonly claimed. What is better supported: antioxidant protection, oil stability, and anti-inflammatory modulation — particularly in the ASU model, where avocado-soybean unsaponifiables show documented anti-inflammatory effects. [PMID 31940989]

The formulation argument for unsaponifiables is real. The skin regeneration argument needs more evidence.

Oil Examples by Unsaponifiable Richness

Olive Oil — The squalene content here is exceptional — up to 50% of the unsaponifiable fraction. That single compound explains the characteristic slip and skin-softening effect that distinguishes olive oil from most other base oils in formulation.

Avocado Oil — High in phytosterols and wax esters, with the strongest direct evidence in the ASU model — avocado unsaponifiables show documented anti-inflammatory activity in clinical and in vitro settings. [PMID 31940989]

Argan Oil — Its sterol profile is unusual — spinasterol and schottenol dominate, compounds rarely found in other botanical oils. Combined with polyphenols and ferulic acid derivatives, this gives argan a distinct antioxidant character that goes beyond its fatty acid profile.

Rice Bran Oil — γ-oryzanol, tocotrienols, ferulic acid, and high phytosterol content make this one of the most complex unsaponifiable fractions among common oils. [PMID 31404986]

Sea Buckthorn Oil — Carotenoid-dominant. The intense orange colour is a direct indicator of how much of the unsaponifiable fraction survived processing — and how much antioxidant activity came with it.

Shea Butter — The triterpene fraction carries most of the functional weight here — barrier-repair and anti-inflammatory activity that the fatty acid profile alone cannot explain.

Practical Formulation Tips

Stabilizing High-PUFA Oils

Seed oils rich in linoleic acid — hemp, rosehip, grapeseed — oxidize quickly. Their own tocopherol fraction provides some protection. Pairing them with a tocopherol-rich base (rice bran, argan) or adding mixed tocopherols extends stability. Dark glass, cool storage — not negotiable.

Anti-Inflammatory Formulations

Phytosterols and triterpenes are the unsaponifiable compounds with the strongest evidence for barrier support and anti-inflammatory activity. In practice, that means building around avocado, shea, and olive — oils where these fractions are well-documented.[PMID 29280987]. The fatty acid base still needs to match the skin type — a triterpene-rich oil in the wrong carrier does not automatically produce a better result. The unsaponifiable fraction works with the fatty acid base, not instead of it.

Sensory Adjustment

Squalane is squalene with its double bonds removed through hydrogenation — shelf-stable, non-comedogenic, and with the same characteristic slip as its parent compound. When a blend feels too heavy or lacks spreadability, squalane adjusts texture without altering the fatty acid profile or adding biological complexity. A small addition — 2–5% — is usually enough to change the skin feel significantly.

Ecologist’s Take

The unsaponifiable fraction is where the argument for cold-pressing is strongest — not as a positioning statement, but as verifiable chemistry.

Refining removes it. Deodorization removes it. Bleaching removes it. What enters formulation from a refined oil is primarily the triglyceride fraction — the fatty acids. Everything else has been processed out.

From a lifecycle perspective, cold-pressed oils require less energy, fewer solvents, and generate cleaner waste streams than solvent-extracted or refined equivalents. The environmental argument and the formulation argument point in exactly the same direction.

Upcycled oils — pressed from seed and fruit waste streams — often retain a rich unsaponifiable fraction precisely because minimal processing is their production logic. Coffee, watermelon, tomato seed oil: their formulation value is partly in the unsaponifiables that survive the press. The environmental cost is front-loaded in the primary supply chain. The cosmetic use is essentially free in lifecycle terms.

The full lifecycle picture is in: upcycled oils in skincare.

Final Thoughts on Unsaponifiables in Natural Oils

The unsaponifiable fraction is not the dominant chemistry of botanical oils — fatty acids carry that weight. But it is the differentiating chemistry. Two oils with identical fatty acid profiles will behave differently in formulation if their unsaponifiable fractions differ. That difference shows up in stability, colour, sensory feel, and anti-inflammatory character.

Understanding the fraction means understanding why cold-pressing matters — not as an ethical position, but as a formulation decision. The tocopherols, sterols, and triterpenes that survive a cold press are exactly what disappears in refining. What you choose to formulate with has a direct consequence on what ends up on skin.

The chemistry behind both fractions — fatty acids and unsaponifiables — is covered in fatty acids profile in skincare and the stability side: iodine number in cosmetics.

If you want to explore more ways to work with natural ingredients and build smarter formulations, you can continue with my guides on DIY Skincare Ingredients, Botanical Oil Guide, or dive deeper into how oils behave in recipes through DIY Skincare Recipes.

References

1. Moore EM, Wagner C, Komarnytsky S. The Enigma of Bioactivity and Toxicity of Botanical Oils for Skin Care. Front Pharmacol. 2020. PMID 32547393
2. Lin TK, Zhong L, Santiago JL. Anti-Inflammatory and Skin Barrier Repair Effects of Topical Application of Some Plant Oils. Int J Mol Sci. 2018. PMID 29280987
3. Salehi B et al. Avocado–Soybean Unsaponifiables: A Panoply of Potentialities to Be Exploited. Molecules. 2020. PMID 31940989
4. Yang R et al. Phytosterol Contents of Edible Oils. Foods. 2019. PMID 31404986
5. Esuoso KO et al. Unsaponifiable Lipid Constituents of Some Underutilized Tropical Seed Oils. J Agric Food Chem. 2000. PMID 10691620
6. Poljšak N et al. Influence of vegetable oils and their constituents on in vitro human keratinocyte and fibroblast proliferation and migration. Sci Rep. 2025.PMID: 40707519