Stigmasterol

Pharmacology & Research

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 on this page is preclinical — there are no human trials of the isolated molecule.

1. Osteoarthritis / anti-inflammatory

The genuine point of difference from beta-sitosterol. In IL-1β-stimulated newborn-mouse and human OA chondrocytes, stigmasterol suppressed IL-6, MMP-3, MMP-13, ADAMTS-4 and PGE₂ and countered IL-1β-induced NF-κB activation ^{1Reference 1Gabay O et al. · 2010Stigmasterol: a phytosterol with potential anti-osteoarthritic propertiesView study →}; a rabbit OA model reported reduced cartilage degradation ^{2Reference 2Chen WP et al. · 2012Stigmasterol blocks cartilage degradation in a rabbit model of osteoarthritisView study →}; and a later study links the protection to downregulation of SREBF2 and reduced chondrocyte ferroptosis ^{3Reference 3Mo Z et al. · 2021Stigmasterol alleviates interleukin-1β-induced chondrocyte injury by downregulating SREBF2 to regulate ferroptosisView study →}.

Gap: entirely preclinical — cell and small-animal only, a single-lab lineage, at supraphysiologic local concentrations, with no human trial and no oral-dosing efficacy given the near-zero systemic absorption ^{1,7Reference 1Gabay O et al. · 2010Stigmasterol: a phytosterol with potential anti-osteoarthritic propertiesView study →Reference 7Li X et al. · 2022The bioavailability and biological activities of phytosterols as modulators of cholesterol metabolismView study →}.

2. Cholesterol (class effect)

Stigmasterol competes with cholesterol for micellar solubilisation and intestinal uptake, and is a minor named component of the sterol mixtures used in LDL-lowering foods. This is a sterol-mixture class effect and lives on beta-sitosterol — not re-argued here ^{5Reference 5Bakrim S et al. · 2022Health benefits and pharmacological properties of stigmasterolView study →}.

Gap: there is no isolated-stigmasterol cholesterol RCT; on its own it is a bit-player in the mixture ^{5Reference 5Bakrim S et al. · 2022Health benefits and pharmacological properties of stigmasterolView study →}.

3. Anticancer

A lupeol-plus-stigmasterol combination suppressed tumour angiogenesis and cholangiocarcinoma growth in mice via TNF-α/VEGFR-2 downregulation ^{4Reference 4Kangsamaksin T et al. · 2017AnimalLupeol and stigmasterol suppress tumour angiogenesis and inhibit cholangiocarcinoma growth in mice via downregulation of tumour necrosis factor-αView study →}, and reviews collate Akt/mTOR and JAK/STAT modulation in other tumour lines ^{5,6Reference 5Bakrim S et al. · 2022Health benefits and pharmacological properties of stigmasterolView study →Reference 62025Research progress on the therapeutic mechanisms of stigmasterol for multiple diseasesView study →}.

Gap: preclinical, frequently tested in combination rather than as a pure isolate, across heterogeneous models, with no clinical signal — hypothesis-generating only ^{4,5Reference 4Kangsamaksin T et al. · 2017AnimalLupeol and stigmasterol suppress tumour angiogenesis and inhibit cholangiocarcinoma growth in mice via downregulation of tumour necrosis factor-αView study →Reference 5Bakrim S et al. · 2022Health benefits and pharmacological properties of stigmasterolView study →}.

4. Metabolic / antidiabetic

Reviews report glucose-lowering and insulin-sensitising signals for stigmasterol ^{5,6Reference 5Bakrim S et al. · 2022Health benefits and pharmacological properties of stigmasterolView study →Reference 62025Research progress on the therapeutic mechanisms of stigmasterol for multiple diseasesView study →}.

Gap: most of this evidence comes from sterol-rich extracts, not the purified molecule, confounded by the whole-plant matrix — do not attribute to the isolate ^{5,6Reference 5Bakrim S et al. · 2022Health benefits and pharmacological properties of stigmasterolView study →Reference 62025Research progress on the therapeutic mechanisms of stigmasterol for multiple diseasesView study →}.

5. Neuroprotective

Reviews cite ROS regulation, acetylcholinesterase inhibition and dopaminergic protection for stigmasterol ^{5,6Reference 5Bakrim S et al. · 2022Health benefits and pharmacological properties of stigmasterolView study →Reference 62025Research progress on the therapeutic mechanisms of stigmasterol for multiple diseasesView study →}.

Gap: the underlying studies are whole-plant/extract models where stigmasterol is one of many compounds, and CNS delivery is implausible given poor absorption — the weakest tier, flagged as speculative ^{5,6Reference 5Bakrim S et al. · 2022Health benefits and pharmacological properties of stigmasterolView study →Reference 62025Research progress on the therapeutic mechanisms of stigmasterol for multiple diseasesView study →}.

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 effect, see beta-sitosterol
TNF-α / VEGFR-2 signalling	↓ tumour angiogenesis (in vivo, combination)	anticancer (preclinical)
iNOS / COX-2, Akt-mTOR, JAK/STAT (review-level)	↓ inflammatory mediators; pro-apoptotic in tumour 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.

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