Sclareolide (Norambreinolide): A Comprehensive Reference Article
1. Identity and Chemical Profile
Nomenclature and Synonyms
Sclareolide (Norambreinolide) is a sesquiterpene lactone natural product derived from various plant sources including Salvia sclarea, Salvia yosgadensis, and cigar tobacco. Synonyms for sclareolide include: (3aR,5aS,9aS,9bR)-decahydro-3a,6,6,9a-tetramethyl-naphtha[2,1-b]furan-2(1H)-one; Norambreinolide; (+)-Norambreinolide; (+)-Sclareolide; (R)-(+)-Sclareolide; and 13,14,15,16-Tetranorlabdano-8α,12-lactone. The compound is registered under CAS number 564-20-5. It is also occasionally referred to by the common name "dionein."
Chemical Classification and Structure
Sesquiterpene lactones are a class of organic compounds characterized by their 15-carbon skeleton and the presence of a lactone ring. Sclareolide has a similar structure and composition to other terpenes and is composed of a tricyclic ring system. The chemical structure of sclareolide consists of different functional groups; importantly, the lactone and decalin moieties are the prime contributors to its biological properties. Lactones are groups of organic compounds with wide ranges of biological properties, including antimicrobial, anti-inflammatory, and anticancer activities.
Sclareolide is a compound prepared by chemical modification or by biotransformation of the labdane-type diterpene sclareol. It is a close analog of sclareol, a plant antifungal compound. Sclareolide is also a precursor of ambroxan, a valuable ambergris fragrance used in perfumery.
Physical Properties and Forms
Sclareolide typically appears as a white crystalline powder. It is supplied as a crystalline solid. A stock solution may be made by dissolving the sclareolide in the solvent of choice; it is soluble in organic solvents such as ethanol, DMSO, and dimethyl formamide (DMF), but is sparingly soluble in aqueous buffers. In industrial and research contexts, the compound is manufactured to purities of 95–98% or higher for use in fragrance, cosmetic, flavor, and pharmaceutical research applications.
Commercial Scale and Availability
Sclareolide is isolated from various plant sources in tons every year and is commercially used as a flavor ingredient in the cosmetic and food industries. In 2016, the consumption volume of sclareolide was up to 100 metric tons in European countries, which represented 82% of its global consumption volume.
2. Botanical Sources
Primary Plant Source: Salvia sclarea (Clary Sage)
Salvia sclarea (Lamiaceae), commonly known as clary sage, belongs to the genus Salvia, one of the most species-rich genera within the family Lamiaceae, comprising more than 1,024 species distributed across temperate, tropical, and subtropical regions worldwide. Clary sage is a biennial (short-lived) herbaceous perennial in the genus Salvia, native to the northern Mediterranean Basin and to some areas in North Africa and Central Asia.
Sclareol is present in the stems, leaves, and flowering parts of clary sage (Salvia sclarea L.). Sclareolide itself is obtained through the chemical or biotransformation conversion of sclareol. Salvia sclarea L. is widely planted for the extraction of sclareol based on commercial purpose for its high content. The plant is rich in bioactive compounds, particularly linalool, linalyl acetate, sclareol, flavonoids, terpenes, and phenolic acids.
Additional Plant Sources
Sclareolide is a sesquiterpene lactone natural product derived from various plant sources including Salvia sclarea, Salvia yosgadensis, and cigar tobacco. The compound has also been reported to occur in species of the genus Nicotiana (tobacco family). Sclareolide is a close analog of sclareol, an antifungal diterpene produced at the leaf surface of Nicotiana spp.
Production Methods
The source of sclareolide can be derived (extracted) naturally from species of the Salvia genus, or can be synthetically obtained as substantially pure sclareolide. There are three synthesis routes of ambroxan from sclareol, in which the classical commercial route includes three reactions and two intermediates — sclareolide and ambradiol. Sclareolide thus occupies a key role both as a naturally occurring compound and as an industrial intermediate in the biosynthesis pathway leading to ambroxan (Ambrox®), one of the most commercially important fragrance chemicals globally.
3. Traditional and Historical Use
Medieval European Traditions
Salvia sclarea presents a long history of medicinal application in Europe, and its name "clary sage" (as a reference to "clear-eye") is a reference to its seeds being used for cleaning the eyes. In medieval Europe, distillates of Salvia sclarea were sold as "muscatel water" for various ailments. Writings from the 15th century, such as those by German herbalist Hieronymus Bock, note its benefits for eye inflammations and digestive upset.
Clary sage has been used since the Middle Ages, where it came to be known as Oculus Christi — the eye of Christ — for its uses as an eye tonic. Over the centuries, clary sage gained prestige as a comprehensive medicinal plant and was highly valued in folk medicine to treat dermatological, digestive, and nervous ailments. In the food field, its fragrance was used to flavor wines, liqueurs, vermouths, and similar products.
Traditional Uses Across Cultures
Traditional uses of S. sclarea include treatment of digestive ailments, skin conditions, menstrual irregularities, and as a natural relaxant in aromatherapy. The traditional use of clary sage dates back to Roman times, when it was used as a herbal remedy to support the digestive and respiratory systems as well as during the menstrual cycle. It was made into a tea and also a poultice for direct application.
Travelers on Silk Road accounts mentioned local use of clary sage in Persia for wound healing — applying crushed leaves as a poultice. The species is used, either as infusion, decoction, or essential oil, to treat digestive, muscular, genitourinary, skin, and circulatory ailments, with applications across multiple conditions. Use of S. sclarea in South Africa has been recorded for its beneficial effects against gastrointestinal and dermatologic ailments, as a decoction.
Important caveat: The traditional uses described above pertain to the whole plant or its preparations (essential oil, tea, decoction), and concern the full botanical matrix of Salvia sclarea — which contains numerous bioactive compounds. Sclareolide as an isolated compound was not identified or used in traditional medicine; its existence as a discrete chemical entity is a product of modern phytochemical analysis. Its association with traditional clary sage use is therefore historical and indirect, mediated through the whole plant.
4. Key Constituents and Active Compounds
Sclareolide as the Focal Compound
Sclareolide is itself the primary active compound under investigation in pharmacological research and as a dietary supplement ingredient, though it co-occurs in plants alongside many other bioactive terpenoids, flavonoids, and phenolic acids. The plant (S. sclarea) is rich in bioactive compounds, including essential oils, flavonoids, terpenes, and phenolic acids, which contribute to its therapeutic properties such as antimicrobial, anti-inflammatory, antioxidant, and neuroprotective effects.
Structural Features Driving Bioactivity
The lactone and decalin moieties are the prime contributors to sclareolide's antifungal properties. Lactones are groups of organic compounds with wide ranges of biological properties, including antimicrobial, anti-inflammatory, and anticancer activities. The alpha,beta-unsaturated lactone functionality, common across sesquiterpene lactones, is generally recognized as capable of interacting with nucleophilic cellular targets such as thiol groups in proteins and enzymes.
Relationship to Sclareol
Sclareolide is a close analog of sclareol, a plant antifungal compound. Much of the mechanistic and pharmacological literature investigates sclareol and sclareolide together or interchangeably, given their structural similarity; however, they are distinct chemical entities and their respective bioactivities are not identical. Researchers note that sclareolide is often used as a scaffold or synthetic starting material for the preparation of structurally modified analogs with enhanced biological activity.
In natural product synthesis, sclareolide is often used as a starting material for the synthesis of many terpenoids and their derivatives.
Cyclic AMP Activity
It is reported that sclareolide, a derivative of sclareol, is effective in increasing cyclic AMP (cAMP) activity. Elevation of intracellular cAMP has been proposed as a mechanism through which sclareolide might influence metabolic rate and body composition, which partly underlies its marketing as a weight management supplement. This cAMP-raising claim has been cited in patent literature but has not been confirmed in rigorous human clinical trials.
5. Scientific Evidence by Area of Use
5.1 Antifungal Activity
Sclareolide has been evaluated for antifungal activity in a range of in vitro and limited in vivo (invertebrate model) studies. All evidence in this domain is preclinical.
Against Cryptococcus neoformans: Sclareolide was assessed against Cryptococcus neoformans H99 and exhibited promising antifungal properties with a minimum inhibitory concentration (MIC) of 16 µg/mL. At MIC × 4 and MIC × 8, sclareolide significantly increased the production of reactive oxygen species (ROS) and reduced the mitochondrial membrane potential (MMP), suggesting oxidative stress and mitochondrial dysfunction in C. neoformans. Sclareolide did not induce caspase-dependent apoptosis, suggesting a non-apoptotic mechanism. Based on the evidence of various experiments, it was confirmed that sclareolide only controls the growth of C. neoformans H99 rather than directly killing the fungal cell. Sclareolide at 128 µg/mL did not exhibit toxicity in Galleria mellonella, further supporting its potential as a safe antifungal agent in this invertebrate model. Further in vivo and pharmacokinetic studies are recommended to explore the potential of sclareolide as a prototype for the development of novel anti-cryptococcal therapies.
Against phytopathogenic fungi: Sclareolide inhibits mycelial growth in the phytopathogenic fungi B. cinerea, F. coeruleum, C. lunata, F. graminearum, and A. brassicae by 33.93%, 67.14%, 27.04%, 46.22%, and 32.48%, respectively, when used at a concentration of 100 µg/mL.
Evidence strength: All antifungal evidence for sclareolide is in vitro or from invertebrate (G. mellonella) models. No human or mammalian in vivo antifungal studies have been published. Evidence is preliminary and hypothesis-generating only.
5.2 Antitumor and Antiproliferative Activity
The most substantial body of published research on sclareolide concerns its potential anticancer properties, though all available evidence remains at the in vitro and animal (xenograft) level.
Pancreatic cancer: The aim of one study (Spandidos Publications, 2017) was to investigate the mechanisms underlying gemcitabine resistance in pancreatic cancer and to select targeted agents combined with gemcitabine to promote its treatment. Panc-1 and ASPC-1 human pancreatic cancer cells were used to establish the experimental model, and HPCCs were exposed to serially increased concentrations of gemcitabine to generate gemcitabine-resistant cells (GR-HPCCs). The anticancer effect of gemcitabine combined with sclareolide was then assessed. Sclareolide upregulated hENT1, downregulated RRM1, and inhibited gemcitabine-induced EMT through the TWIST1/Slug pathway in the GR-HPCCs. In addition, sclareolide mediated the NOTCH1 intracellular cytoplasmic domain (NICD)/glioma-associated oncogene 1 (Gli1) pathway, which triggered TWIST1/Slug–hENT1/RRM1 signaling and resensitized GR-HPCCs to gemcitabine. Sclareolide resensitized GR-HPCCs to gemcitabine through inducing apoptosis; in vivo, the co-administration of sclareolide and gemcitabine effectively suppressed tumor growth.
The concentrations tested in this in vitro study were 5, 10, and 20 µM in gemcitabine-resistant PANC-1 and AsPC-1 human pancreatic cancer cells.
Leukemia cell lines: The antiproliferative activities of selected sclareolide–indole conjugates were tested in K562 and MV4-11 cancer cell lines. Cytometric flow analysis showed that lead compounds 8k and 10 induced robust apoptosis in MV4-11 cancer cells, while they exhibited weak impact on cell cycle progression. Notably, in this study, unmodified sclareolide itself was used as a reference compound, with the synthetic conjugates demonstrating substantially greater antiproliferative potency than the parent molecule.
Evidence strength: Sclareolide is isolated from various plant sources in tons every year and commercially used as a flavor ingredient; antitumor and antiviral activities of sclareolide have been previously reported. However, all anticancer evidence is in vitro or from animal xenograft models. No human clinical trials examining sclareolide's anticancer effects have been published. Evidence is preliminary and limited to laboratory settings.
5.3 Antiviral Activity
In one study, sclareol and sclareolide, two natural products in Salvia sclarea, were identified as Ebola virus (EBOV) entry inhibitors with EC50 values of 2.4 µmol/L and 8.0 µmol/L, respectively, through blocking the viral fusion process. Sclareolide blocked the Ebola virus fusion process with an inhibitory EC50 value of 8.0 µM and exhibited wide-spectrum activities against an additional seven filoviruses.
The precise mechanism involves interference with viral glycoprotein-mediated cell entry. Sclareolide is described as an Ebola virus entry inhibitor that reduces infection of HEK293T cells by an HIV-based virus system pseudotyped with Ebola virus glycoprotein (EC50 = 8 µM).
Evidence strength: All antiviral evidence is from in vitro pseudovirus assay systems. No animal or human trials of sclareolide as an antiviral agent have been reported. These findings are exploratory and very early stage.
5.4 Anti-inflammatory Activity
The anti-inflammatory activity of sclareol and sclareolide has been described in patent literature. The anti-inflammatory activity is supported by inhibition of 5-lipoxygenase as well as cyclooxygenase-1 (COX-1) activity.
Sclareolide inhibits nitric oxide production in LPS-stimulated BV-2 cells, with an IC50 of 20.3 µM. Sclareol (the closely related parent compound) significantly suppresses the overproduction of reactive nitrogen and oxygen species by inhibiting nitric oxide (NO) release and reducing lipid peroxidation. At the transcriptional and protein levels, sclareol downregulates inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), thereby limiting ROS/RNS-driven inflammatory amplification in activated macrophages.
In preclinical models of rheumatoid arthritis, a human synovial cell line (SW982) and an experimental murine model of rheumatoid arthritis (collagen-induced arthritis, CIA) were utilized to evaluate sclareol's therapeutic effects. Arthritic DBA/1J mice were dosed with 5 and 10 mg/kg sclareol intraperitoneally every other day over 21 days. Results reveal that serum anti-CII antibody, cytokines IL-1β, IL-6, TNF-α, and IL-17, as well as Th17 and Th1 cell populations in inguinal lymph nodes, were significantly lower in sclareol-treated mice compared to the control group. Sclareol treatment groups also showed reduced paw swelling and lower histological arthritic scores. In IL-1β-stimulated SW982 cells, secretion of inflammatory cytokines (TNF-α and IL-6) was reduced, associated with the downregulation of p38-MAPK, ERK, and NF-κB pathways.
Evidence strength: Anti-inflammatory activity of sclareolide and the closely related sclareol has been demonstrated in cell-based (in vitro) assays and animal models. No published human clinical trials specifically on sclareolide's anti-inflammatory effects are available. This body of evidence is preclinical.
5.5 Antimicrobial (Antibacterial / Antiacne) Activity
The anti-microbial activity of sclareolide and sclareol has been described in earlier patent literature, concluding that sclareolide and sclareol are potentially useful to treat acne, dermatitis, and undesirable body odour. The use of sclareolide within a natural combination of five components to treat acne has also been proposed in patent applications. These patent-based claims remain to be validated by independent peer-reviewed clinical trials.
5.6 Cell Differentiation Enhancement (Cosmetic Applications)
The use of sclareolide as a cell differentiation enhancer has been disclosed in patent applications. As sclareolide is used itself as a fragrance material, it is often a component of cosmetic formulations. In the cosmetics industry it is valued both for its organoleptic properties and for claimed skin-conditioning activity, though clinical substantiation of cosmetic efficacy claims remains limited in the peer-reviewed literature.
5.7 Weight Loss / Body Composition Claims
Sclareolide has been marketed in dietary supplement products, sometimes promoted as a weight-loss or body-composition-altering ingredient. It is used as a fragrance in cosmetics and has been more recently marketed as a weight loss supplement, though there is no clinical evidence to support this effect. The theoretical basis for weight management claims rests on the reported cAMP-elevating property of sclareolide, with the reasoning that elevated cAMP could stimulate lipolysis — a mechanism that has not been tested in adequately powered human clinical trials for this compound. The assertion from Wikipedia is corroborated by the complete absence of controlled clinical studies on sclareolide's effects on human body weight or body composition in the peer-reviewed literature.
6. Mechanisms of Action
Oxidative Stress Induction (Antifungal)
Sclareolide showed promising antifungal effects through triggering the oxidative stress-related pathways of C. neoformans H99 cells, as evidenced by reduced mitochondrial membrane potential (MMP). The amount of oxidative stress developed during sclareolide treatment was not enough to induce cell death. However, this impacted cellular components like DNA, proteins, and lipids, contributing to the fungistatic action of sclareolide.
Membrane Integrity Disruption
Propidium iodide (PI) accumulation assays indicated a reduction in C. neoformans membrane integrity following sclareolide treatment. This suggests that membrane permeabilization, even if not to a cell-death-inducing extent at lower concentrations, is a component of its fungistatic mechanism.
NOTCH/Hedgehog Pathway Modulation (Anticancer)
Sclareolide reversed the mediating effects of TWIST1 and Slug on hENT1 and RRM1 through the inhibition of TWIST1 and Slug, and inhibited the epithelial-to-mesenchymal transition (EMT) phenotype in GR-HPCCs treated with gemcitabine. These pathways are known to regulate cancer cell plasticity and drug resistance.
Cyclooxygenase and Lipoxygenase Inhibition (Anti-inflammatory)
The anti-inflammatory activity of sclareolide is supported by inhibition of 5-lipoxygenase as well as cyclooxygenase-1 (COX-1) activity. These are key enzymes in the arachidonic acid cascade responsible for the biosynthesis of prostaglandins and leukotrienes, both central mediators of inflammation. Inhibition of iNOS-driven nitric oxide production has also been characterized in in vitro macrophage stimulation models.
Viral Fusion Blockade (Antiviral)
Sclareolide was identified as an EBOV entry inhibitor through blocking the viral fusion process. The mechanism is consistent with interference at the level of the viral glycoprotein interaction with host cell membranes during endosomal entry, though the precise molecular target has not been fully characterized.
cAMP Elevation
It is reported that sclareolide, a derivative of sclareol, is effective in increasing cyclic AMP activity. Cyclic AMP is a second messenger that activates protein kinase A (PKA), which in turn can phosphorylate hormone-sensitive lipase to promote triglyceride breakdown (lipolysis). This mechanism is proposed as the basis for alleged body-composition effects, but has not been validated in peer-reviewed human studies.
7. Body Systems and Health Areas of Association
- Immune and inflammatory system: In vitro and animal data suggest modulation of NF-κB, MAPK, COX-1/2, 5-lipoxygenase, and iNOS pathways; potential relevance to inflammatory conditions including rheumatoid arthritis (sclareol preclinical data).
- Oncology (experimental): Preclinical evidence of antiproliferative and chemosensitizing effects in pancreatic cancer, leukemia, and other cell lines in laboratory settings.
- Antifungal defense: In vitro evidence of fungistatic activity against Cryptococcus neoformans and phytopathogenic fungi via oxidative stress and membrane integrity disruption.
- Virology (experimental): In vitro evidence of Ebola and filovirus entry inhibition.
- Skin/cosmetic: Formulated as a fragrance and skin-conditioning ingredient in cosmetics; topical formulations proposed for acne and skin differentiation in patents.
- Metabolic / body composition (unsubstantiated in humans): Claimed cAMP-elevating mechanism proposed for fat metabolism; no human clinical data exist to support efficacy.
8. Dosage Forms and Dosages Reported in Studies
No established human therapeutic dose or human clinical trial dosing regimen for sclareolide has been published in the peer-reviewed literature. The following dosages are those reported in specific experimental (in vitro and animal) studies only:
- Pancreatic cancer cells (in vitro): Sclareolide tested at 5, 10, and 20 µM in gemcitabine-resistant PANC-1 and AsPC-1 human pancreatic cancer cells.
- Anti-inflammatory (in vitro): Sclareolide inhibits nitric oxide production in LPS-stimulated BV-2 cells with an IC50 of 20.3 µM.
- Antifungal (in vitro): Sclareolide tested against phytopathogenic fungi at 100 µg/mL.
- Antifungal (C. neoformans, in vitro): Minimum inhibitory concentration of 16 µg/mL.
- Antiviral (EBOV, in vitro): EC50 of 8.0 µmol/L for Ebola virus entry inhibition.
- Rheumatoid arthritis (animal model): Sclareol (closely related analog) administered at 5 and 10 mg/kg intraperitoneally every other day over 21 days in arthritic DBA/1J mice.
- In vivo toxicology (G. mellonella): Sclareolide at 128 µg/mL did not exhibit toxicity in Galleria mellonella larvae.
Dietary supplement products have historically contained varying amounts of sclareolide. Currently, there are several products containing sclareolide, including Xenadrine 40+ available from Cytodyne LLC and HOT-ROXâ„¢. No peer-reviewed dose-finding or dose-response studies in humans have been published to guide supplementation dosing.
9. Safety Considerations
Toxicological Data (Animal and Invertebrate Models)
The neurotoxicity of free sclareol was found in tumor-bearing mice with colon cancer HCT116 cells at doses over 560 mg/kg, whereas 50 mg/kg sclareol was observed to be ineffective in inducing toxicity. These findings pertain to sclareol (the diterpene parent compound) rather than sclareolide (the sesquiterpene lactone), but given their structural close relationship they are contextually relevant. In the invertebrate model, sclareolide at 128 µg/mL did not exhibit toxicity in Galleria mellonella.
Bioavailability Constraints
The low bioavailability of sclareol, attributed to its poor water solubility (0.0012 g/L), is considered the main obstacle limiting its clinical application. Structure modification and nano-delivery systems have been explored for enhancing bioactivities and pharmacokinetic properties, such as water solubility and distribution. Sclareolide shares similar water-insolubility, as reflected in laboratory data showing it is soluble in organic solvents such as ethanol, DMSO, and dimethyl formamide, but sparingly soluble in aqueous buffers.
Pharmacokinetics
Pharmacokinetic studies on sclareol suggested that it is mainly distributed in extracellular fluid (apparent distribution volume was 21.4 L/kg), and its half-life was short (6.0 h) in rats following intravenous injection at 5.0 mg/kg. No pharmacokinetic data for sclareolide itself in humans or mammals have been published.
Absence of Human Safety Data
No controlled human clinical trials evaluating the safety, tolerability, or pharmacology of orally administered sclareolide as a supplement have been published in the peer-reviewed literature. Currently available products containing sclareolide have been noted in patent literature as providing limited benefit, with one reason identified as the inadequate amount and quality (potency, stability, and bioactivity) of the sclareolide present in commercially available products.
Regulatory Status
Sclareolide is commercially used as a flavor ingredient in the cosmetic and food industries. In its cosmetic and flavor industry roles, it is subject to relevant industry safety evaluations (e.g., IFRA guidelines for fragrances). As a dietary supplement ingredient promoted for weight loss or body-composition effects, it has not received regulatory approval from the U.S. FDA or European Medicines Agency (EMA) for any therapeutic indication. The FDA has not issued any specific safety guidance monograph on sclareolide as a supplement ingredient as of the available literature.
Potential Interactions and Considerations
Given sclareolide's demonstrated in vitro inhibition of COX-1 and 5-lipoxygenase, and its structural relationship to bioactive sesquiterpene lactones, the theoretical potential for interaction with non-steroidal anti-inflammatory drugs (NSAIDs), anticoagulants, or other COX-pathway modifiers warrants attention — although no human interaction studies have been conducted. The poor aqueous solubility of sclareolide raises questions about oral bioavailability of supplement forms, which has not been characterized in human pharmacokinetic studies.
10. Use in Research and Industrial Synthesis
Antitumor and antiviral activities of sclareolide have been previously reported; however, biological studies of sclareolide synthetic analogs are few. Sclareolide has become increasingly important as a chiral building block in synthetic organic chemistry. In natural product synthesis, sclareolide is often used as a starting material for the synthesis of many terpenoids and their derivatives. Studies suggest that sclareolide could be a good template and substrate for the synthesis of novel antiproliferative compounds.
It is widely employed in the fragrance industry, valued for its warm, woody, and ambergris-like aroma, often used as a sustainable substitute for natural ambergris. Sclareolide is a precursor of ambroxan, a valuable ambergris fragrance used in perfumery, and is also used itself as a fragrance material in cosmetic formulations.
Summary of Evidence Quality
The overall evidence base for sclareolide as a dietary supplement or therapeutic agent is at an early, primarily preclinical stage. Published evidence consists almost entirely of in vitro cell culture studies and, in a limited number of cases, animal xenograft or invertebrate model studies. The most active areas of research are antifungal activity (particularly against C. neoformans), antiproliferative effects in cancer cell lines, and antiviral activity against filoviruses. For all of these areas, no human clinical trial data are available. Claims regarding weight loss or body composition improvement, which have driven consumer marketing of sclareolide supplements, have not been evaluated in any published controlled human trial, and Wikipedia explicitly notes that no clinical evidence exists to support this application.
References
Go back