Faradiol

Pharmacology & Research

Faradiol is a pentacyclic triterpenediol of calendula flowers — a relative of lupeol and taraxasterol — and the principal topical anti-inflammatory constituent of the flower’s lipophilic fraction. Two framing points. In the floret it occurs mainly as its C-3 fatty-acid monoesters (the pharmacopoeial QC marker), while the free diol is the more active aglycone — so keep this free-diol entry distinct from the “faradiol monoesters” marker. And its evidence, though genuinely notable, is entirely preclinical and topical: there are no human trials of the isolate, and calendula’s clinical use rests on the whole extract/ointment.

1. Topical anti-inflammatory / anti-oedematous

The marquee application and the reason ester content is calendula’s pharmacopoeial QC marker. Della Loggia (1994) fractionated the flower’s lipophilic extract and localised the topical anti-oedematous activity to the triterpenediol monoesters — free faradiol being the most active single compound, with esters and monool triterpenes weaker ^{1Reference 1Della Loggia R et al. · 1994The role of triterpenoids in the topical anti-inflammatory activity of Calendula officinalis flowersView study →} — and Zitterl-Eglseer (1997) confirmed the anti-oedematous ranking of the main triterpendiol esters, roughly comparable weight-for-weight to indomethacin ^{2Reference 2Zitterl-Eglseer K et al. · 1997Anti-oedematous activities of the main triterpendiol esters of marigold (Calendula officinalis)View study →}.

Gap: rodent topical oedema models only; the indomethacin comparison is weight-for-weight in one acute assay, not therapeutic equivalence, and human anti-inflammatory use is documented only for the whole calendula preparation ^{1,4Reference 1Della Loggia R et al. · 1994The role of triterpenoids in the topical anti-inflammatory activity of Calendula officinalis flowersView study →Reference 4Ukiya M et al. · 2006Anti-inflammatory, anti-tumour-promoting and cytotoxic activities of constituents of marigold (Calendula officinalis) flowersView study →}.

2. Anti-tumour-promotion

Marigold flower triterpenoids including the faradiol esters showed anti-tumour-promoting and cytotoxic activity in standard chemoprevention screens (EBV-EA activation / two-stage carcinogenesis) ^{4Reference 4Ukiya M et al. · 2006Anti-inflammatory, anti-tumour-promoting and cytotoxic activities of constituents of marigold (Calendula officinalis) flowersView study →}.

Gap: a single study at the in-vitro/short-term-promotion-assay level, with faradiol one of several constituents tested and no animal tumour-burden or clinical data — not an anticancer indication ^{4Reference 4Ukiya M et al. · 2006Anti-inflammatory, anti-tumour-promoting and cytotoxic activities of constituents of marigold (Calendula officinalis) flowersView study →}.

3. Wound healing

Faradiol esters mark the lipophilic anti-inflammatory triterpenoid fraction of calendula, whose ointments are used topically for wounds ^{1,5Reference 1Della Loggia R et al. · 1994The role of triterpenoids in the topical anti-inflammatory activity of Calendula officinalis flowersView study →Reference 52025New insights into the analysis of faradiol esters and related compounds in CalendulaView study →}.

Gap: no isolated-faradiol wound-healing study exists — calendula’s measured fibroblast-proliferation/wound activity is largely driven by its hydrophilic flavonol-glycoside fraction, a chemically distinct part, so faradiol’s role is a plausible contributor, not demonstrated ^{5Reference 52025New insights into the analysis of faradiol esters and related compounds in CalendulaView study →}.

4. Antioxidant

Chemically modified calendula triterpene derivatives were screened alongside anti-inflammatory endpoints ^{3Reference 3Neukirch H et al. · 2005Improved anti-inflammatory activity of three new terpenoids derived by systematic chemical modification from the abundant triterpenes of Calendula officinalisView study →}.

Gap: faradiol is not a notable antioxidant — calendula’s antioxidant capacity is a phenolic/flavonoid property — so this is a minor mention only ^{3Reference 3Neukirch H et al. · 2005Improved anti-inflammatory activity of three new terpenoids derived by systematic chemical modification from the abundant triterpenes of Calendula officinalisView study →}.

Mechanisms

Target / pathway	Effect	Relevant to
Croton-oil / TPA acute oedema (topical)	suppressed; faradiol/monoester most active of the fraction, ≈ indomethacin w/w	topical anti-inflammatory (the only well-supported mechanism)
Arachidonic-acid / eicosanoid cascade (inferred)	anti-oedematous action consistent with, but not molecularly mapped to, eicosanoid modulation	topical anti-inflammatory (mechanism unresolved)
EBV-EA activation / carcinogenesis promotion	inhibited; cytotoxic to some tumour lines	anti-tumour-promotion (screen only)

Honest note: only the topical anti-oedematous effect is genuinely supported; the upstream molecular target for faradiol has not been pinned down — the classic work is phenotypic (oedema assay), not target-level.

Pharmacokinetics

There is no dedicated pharmacokinetic study of isolated faradiol. It is a highly lipophilic pentacyclic triterpenediol (class-typical of lupeol/taraxasterol: very low aqueous solubility, high logP), so topical delivery is the pharmacologically relevant route — the entire evidence base is topical/local, matching calendula ointment use — and oral bioavailability is expected to be poor, meaning in-vitro/topical potencies should not be read as oral human efficacy. In the plant it exists mainly esterified (C-3 myristate/palmitate/laurate), and this ester-versus-free-diol distinction matters for both QC and any absorption assumptions; no human ADME, metabolism or half-life data exist.

Clinical trials

There are no trials of isolated faradiol or its monoesters. All human evidence is for whole calendula preparations (extracts/ointments), where faradiol esters are a standardised marker but not an isolated intervention — no trial should be attributed to faradiol itself.

Last checked: July 2026.

Toxicity & Safety

Faradiol has a [low] toxicity verdict — consistent with a dietary/topical plant triterpene, with no signal of acute toxicity in the calendula bioassays and a benign topical safety record for calendula, of which the faradiol esters are constituents. There are no genotoxicity, carcinogenicity or repeat-dose toxicology data on the pure isolate (the reported tumour-cell cytotoxicity is an anticancer-screening readout, not evidence of systemic toxicity). Contact sensitisation to calendula/Asteraceae is possible at the whole-plant level (sesquiterpene lactones, not faradiol), and is relevant to the source herb rather than to faradiol specifically.

Pregnancy & lactation

Avoid the isolate (precautionary). There are no data on isolated faradiol, and oral calendula is traditionally cautioned against in pregnancy (emmenagogue reputation for the whole herb); topical calendula preparations are generally low-concern, but that judgement applies to the finished herbal product, not a concentrated isolate.

Dosage

There is no established human dose — there is no isolated-faradiol dosing in humans, the evidence is topical and preclinical, and the ”≈ indomethacin” figure is a weight-for-weight comparison in the mouse-ear oedema assay, not a therapeutic dose. In practice faradiol is delivered within standardised calendula preparations, where faradiol-monoester content is the pharmacopoeial QC parameter rather than a dosed active.

References

1. Della Loggia R, et al. (1994). The role of triterpenoids in the topical anti-inflammatory activity of Calendula officinalis flowers. Planta Medica. https://pubmed.ncbi.nlm.nih.gov/7809203/
2. Zitterl-Eglseer K, et al. (1997). Anti-oedematous activities of the main triterpendiol esters of marigold (Calendula officinalis). Journal of Ethnopharmacology. https://pubmed.ncbi.nlm.nih.gov/9254116/
3. Neukirch H, et al. (2005). Improved anti-inflammatory activity of three new terpenoids derived by systematic chemical modification from the abundant triterpenes of Calendula officinalis. Chemistry & Biodiversity. https://pubmed.ncbi.nlm.nih.gov/17192009/
4. Ukiya M, et al. (2006). Anti-inflammatory, anti-tumour-promoting and cytotoxic activities of constituents of marigold (Calendula officinalis) flowers. Journal of Natural Products. https://pubmed.ncbi.nlm.nih.gov/17190444/
5. (2025). New insights into the analysis of faradiol esters and related compounds in Calendula. Journal of Pharmaceutical and Biomedical Analysis. https://pubmed.ncbi.nlm.nih.gov/40120297/