Stigmasterol

Stigmasterol at a Glance

Stigmasterol is a ubiquitous plant sterol and a close relative of beta-sitosterol, differing by one extra side-chain double bond.

Like all phytosterols it is barely absorbed — which is what makes its most interesting preclinical finding awkward. Its chondroprotective and anti-osteoarthritis activity, suppressing cartilage degradation, would require the compound to reach the joint, and its absorption profile argues against that happening from an oral dose.

What It's Used For

Stigmasterol is a phytosterol that occurs alongside beta-sitosterol across a very wide range of plants, differing from it by a single extra side-chain double bond (the Δ22 bond). Two framing points. First, like all phytosterols it is barely absorbed — on the order of ~1% of an oral dose — so its systemic pharmacology is inherently limited ^{7Reference 7Li X et al. · 2022The bioavailability and biological activities of phytosterols as modulators of cholesterol metabolismView study →}.

Second, the phytosterol cholesterol-lowering story is a sterol-mixture class effect and is covered on the beta-sitosterol page; it is not re-argued here. What makes stigmasterol worth its own page is a distinct, genuinely stigmasterol-specific preclinical dataset: chondroprotection in osteoarthritis models, where it suppresses cartilage-degrading enzymes via NF-κB ^{1Reference 1Gabay O et al. · 2010Stigmasterol: a phytosterol with potential anti-osteoarthritic propertiesView study →}.

Everything here is preclinical — there are no human trials of the isolated molecule.

A real point of difference from sitosterol:stigmasterol protects cartilage in OA cell and animal models, suppressing IL-6, MMP-3/13 and ADAMTS-4 via NF-κB and an SREBF2/ferroptosis axis ^{1,3Reference 1Gabay O et al. · 2010Stigmasterol: a phytosterol with potential anti-osteoarthritic propertiesView study →Reference 3Mo Z et al. · 2021Stigmasterol alleviates interleukin-1β-induced chondrocyte injury by downregulating SREBF2 to regulate ferroptosisView study →} — its most distinctive signal.

Cholesterol is a class effect, not this molecule’s:the LDL-lowering evidence is for sterol mixtures and lives on beta-sitosterol; stigmasterol is a minor named component.

The honest headline:near-zero oral bioavailability ^{7Reference 7Li X et al. · 2022The bioavailability and biological activities of phytosterols as modulators of cholesterol metabolismView study →} means every preclinical effect is local/in-vitro, with no systemic human exposure to support a clinical claim, and no human trials exist.

Evidence by IndicationStrength of support · Beta

Support is an experimental score — weighted by study type (human > animal > in vitro) and volume. A beta, not a validated metric. Every isolated-stigmasterol application is preclinical, so scores stay low by design. Each application links to its write-up.

Mechanisms

Target / pathway	Effect	Relevant to
NF-κB (chondrocytes)	↓ IL-6, MMP-3/13, ADAMTS-4, PGE₂ → less cartilage degradation	osteoarthritis
SREBF2 / ferroptosis axis	↓ SREBF2 → reduced IL-1β-induced chondrocyte ferroptosis	osteoarthritis
Intestinal cholesterol-absorption competition	↓ cholesterol absorbed (as part of a sterol mixture)	cholesterol — class effectsee beta-sitosterol
TNF-α / VEGFR-2 signaling	↓ tumor angiogenesis (in vivo, combination)	anticancer (preclinical)
iNOS / COX-2, Akt-mTOR, JAK/STAT (review-level)	↓ inflammatory mediators; pro-apoptotic in tumor lines	anti-inflammatory / anticancer (unconfirmed for isolate)

Pharmacokinetics

Load-bearing. Stigmasterol behaves like other Δ5 phytosterols: absorption is very poor — on the order of ~1% or less of an oral dose — further limited relative to cholesterol by its bulky 24-ethyl side chain and the extra Δ22 double bond, while the ABCG5/ABCG8 efflux pumps actively return absorbed sterol to the gut lumen and bile, keeping plasma levels minuscule ^{7Reference 7Li X et al. · 2022The bioavailability and biological activities of phytosterols as modulators of cholesterol metabolismView study →}. The consequence: the impressive osteoarthritis and anticancer effects are all preclinical and mostly local or in-vitro, because there is essentially no systemic exposure from oral stigmasterol to support a systemic clinical effect. The disorder that proves the rule is sitosterolemia (loss-of-function ABCG5/G8), where all plant sterols — stigmasterol included — accumulate 30–100-fold with pathological consequences.

Clinical trials

There are no human trials of isolated stigmasterol for any indication. The only human phytosterol trials (cholesterol lowering) used sterol/stanol mixtures in which stigmasterol is a minor named constituent — those belong to the phytosterol class and are covered on beta-sitosterol. All stigmasterol-specific evidence is cell-culture or animal.

Completed	Planned	Terminated	Preclinical
—(isolate); sterol-mixture only	—	—	Moderate

Last checked: July 2026.

Toxicity & Safety

Stigmasterol is a normal dietary phytosterol, consumed in grams-per-week from vegetable oils, nuts, seeds and legumes, and is not flagged as toxic in any source-herb monograph; because oral absorption is negligible, systemic toxicity from dietary or supplemental intake is expected to be minimal. Two class-level caveats apply rather than isolate-specific alarms. As with all phytosterols, thermally or oxidatively degraded stigmasterol forms oxyphytosterols in heated/stored oils — it is these oxidation products, not the parent sterol, that carry preclinical safety interest. And in the rare sitosterolemia disorder, stigmasterol accumulates with other plant sterols and contributes to the pathology, a reason not to assume “more absorbed sterol is better” (full treatment on the beta-sitosterol page). Its interactions are the phytosterol class ones: it competes at the NPC1L1 uptake step (mechanistically overlapping ezetimibe) and, as part of a sterol load, can modestly lower absorption of carotenoids and vitamin E. There is no isolate-specific drug-interaction data.

Dosage

There is no established human dose for isolated stigmasterol, and nothing here is a recommendation. Research used 20 µg/mL in chondrocyte culture (the osteoarthritis lead) ^{1Reference 1Gabay O et al. · 2010Stigmasterol: a phytosterol with potential anti-osteoarthritic propertiesView study →}, with animal OA and oncology models using experimental doses not translatable to humans ^{2,4Reference 2Chen WP et al. · 2012Stigmasterol blocks cartilage degradation in a rabbit model of osteoarthritisView study →Reference 4Kangsamaksin T et al. · 2017AnimalLupeol and stigmasterol suppress tumour angiogenesis and inhibit cholangiocarcinoma growth in mice via downregulation of tumour necrosis factor-αView study →}; any oral “dose” is undercut by the ~1% absorption ceiling. Where phytosterol dosing is meaningful it is the ~2 g/day sterol-mixture cholesterol regimen, which belongs to the class and is documented on beta-sitosterol.

References

Gabay O, Sanchez C, Salvat C, et al. (2010). Stigmasterol: a phytosterol with potential anti-osteoarthritic properties. Osteoarthritis and Cartilage. https://pubmed.ncbi.nlm.nih.gov/19786147/
Chen WP, Yu C, Hu PF, Bao JP, et al. (2012). Stigmasterol blocks cartilage degradation in a rabbit model of osteoarthritis. Acta Biochimica Polonica. https://pubmed.ncbi.nlm.nih.gov/23074702/
Mo Z, Xu P, Li H (2021). Stigmasterol alleviates interleukin-1β-induced chondrocyte injury by downregulating SREBF2 to regulate ferroptosis. Bioengineered. https://pubmed.ncbi.nlm.nih.gov/34806937/
Kangsamaksin T, et al. (2017). Lupeol and stigmasterol suppress tumour angiogenesis and inhibit cholangiocarcinoma growth in mice via downregulation of tumour necrosis factor-α. PLoS One. https://pubmed.ncbi.nlm.nih.gov/29232409/
Bakrim S, Benkhaira N, Bourais I, et al. (2022). Health benefits and pharmacological properties of stigmasterol. Antioxidants (Basel). https://pubmed.ncbi.nlm.nih.gov/36290632/
Li J, Zheng X, Qi J (2025). Research progress on the therapeutic mechanisms of stigmasterol for multiple diseases. Molecules. https://pubmed.ncbi.nlm.nih.gov/40363681/
Li X, Xin Y, Mo Y, et al. (2022). The bioavailability and biological activities of phytosterols as modulators of cholesterol metabolism. Molecules. https://pubmed.ncbi.nlm.nih.gov/35056839/