Bisabolene

Bisabolene: A Comprehensive Reference

1. Identity and Chemical Classification

Bisabolenes are a group of closely related natural chemical compounds belonging to the sesquiterpene class of terpenes. Bisabolenes are a group of closely related natural chemical compounds classified as sesquiterpenes, produced from farnesyl pyrophosphate (FPP) and present in the essential oils of bisabol and a wide variety of other plants including cubeb, lemon, and oregano. The term "bisabolene" refers generically to the parent hydrocarbon skeleton, though in scientific use it encompasses three structurally distinct isomers. Three isomers are known — α-, β-, and γ-bisabolene — which differ by the positions of their double bonds.

The molecular formula of bisabolene isomers is C₁₅H₂₄, reflecting a 15-carbon sesquiterpene framework. The isoprenoid bisabolene is one of the simplest monocyclic sesquiterpenes and is a natural plant product that, in addition to its biological function, serves as a precursor for many industrial products. Structurally, bisabolanes are a family of naturally occurring sesquiterpenoids featuring a hexatomic ring core. The CAS registry number assigned to the commercial bisabolene mixture is 495-62-5. There are insufficient direct toxicity data on bisabolene (CAS # 495-62-5), and in silico evaluation has been conducted to determine read-across analogs for this material.

Each isomer carries distinct physicochemical properties. β-Bisabolene has a balsamic odor and is approved in Europe as a food additive. α-Bisabolene's distinctive aroma is highly prized in fragrances and cosmetics, while its antioxidant properties hold significant pharmaceutical potential.

Bisabolene is closely related to, but chemically distinct from, bisabolol (an alcohol derivative). The most commercially prominent related compound is α-bisabolol (levomenol), an unsaturated monocyclic sesquiterpene alcohol that arises from bisabolene by further enzymatic oxidation. Alpha-bisabolol (α-bisabolol), an unsaturated monocyclic sesquiterpene alcohol, is known as one of the "most-used herbal constituents" in the world. When reviewing the scientific literature, researchers frequently treat the bisabolene hydrocarbons and the bisabolol alcohols as part of the same bisabolane sesquiterpenoid family; this article covers the bisabolene hydrocarbons primarily but includes closely relevant data on bisabolol-type chemistry where it illuminates bisabolene's biology.

2. Natural Sources and Distribution

2.1 Plant Sources

Many bisabolane-type sesquiterpenoids have been obtained from terrestrial plants, marine invertebrates, and their symbiotic microorganisms. Since 1985, more than 350 bisabolane-type sesquiterpenoids have been isolated, primarily from species in the families Compositae, Zingiberaceae, Phyllanthaceae, Apiaceae, Aspergillaceae, Halichondriidae, and Aplysiidae.

• Conifers (Abies, Picea spp.): (E)-α-Bisabolene synthase is one of two wound-inducible sesquiterpene synthases of grand fir (Abies grandis), and the olefin product of this cyclization reaction is considered to be the precursor in Abies species of todomatuic acid, juvabione, and related insect juvenile hormone mimics. The JBEI research team identified that bisabolene is produced in small quantities by spruce and fir trees.
• Copaiba (Copaifera spp.): C. reticulata oleoresin collected in the Amazonian summer contained six major sesquiterpene compounds — β-bisabolene, cis-eudesma-6,11-diene, trans-α-bergamotene, β-selinene, α-selinene, and β-elemene — and β-bisabolene was the major volatile compound at 25.15%.
• Opoponax (Commiphora guidottii): β-Bisabolene, a sesquiterpene constituting 5% of the essential oil, exhibited selective cytotoxic activity for mouse and human breast cancer cells.
• Black pepper (Piper nigrum): α-Bisabolene is a primary component in black pepper (Piper nigrum).
• Sunflower (Helianthus annuus): Sunflower is known to produce a variety of bisabolene-type sesquiterpenes and accumulates these substances in trichomes of leaves, stems, and flowering parts.
• German Chamomile (Matricaria recutita): The key compounds in the essential oil of German chamomile are α-bisabolol, chamazulene, and germacrene D, among others. Bisabolene serves as the immediate biosynthetic precursor to α-bisabolol in this plant.
• Turmeric (Curcuma longa): Special sesquiterpene polymers synthesized via the polymerization of curcumin and bisabolane-type sesquiterpenoids have been isolated from turmeric.
• Apiaceae family (Ligusticum, Angelica): Nine bisabolane-type sesquiterpenoids have been reported from the genera Ligusticum and Angelica in the family Apiaceae.
• Psammogeton canescens: β-Bisabolene was the main constituent (25%) of the essential oil of P. canescens, followed by α-pinene (20%), apiole (15.34%), and other minor compounds.
• Colquhounia coccinea var. mollis: A Lamiaceae medicinal plant from which a high-fidelity (R)-β-bisabolene synthase gene was characterized. The sesquiterpene β-bisabolene possessing R and S configurations is commonly found in plant essential oils with antimicrobial and antioxidant activities.

2.2 Marine and Fungal Sources

Bisabolenes are produced by several fungi, though their biological role in that group of organisms remains unclear. Bisabolane-type sesquiterpenoids, especially those isolated from marine organisms, are considered nonnegligible natural products both structurally and biologically. A systematic review summarized 296 newly reported bisabolanes characterized from fungi, marine algae, soft corals, marine sponges, terrestrial plants, and other sources, among which 94 members were isolated from marine organisms. Specific marine examples include red algae of the genus Laurencia and tropical soft corals such as Pseudopterogorgia rigida. Antibacterial activity is one of the most significant properties of bisabolane-type sesquiterpenoids. Most bisabolene-type sesquiterpenoids with antibacterial activity have been isolated from fungi, and have been shown to inhibit a variety of marine and terrestrial pathogens, both bacterial and fungal.

2.3 Insect Pheromone Roles

Various bisabolene derivatives also function as pheromones in different insects, such as stink bugs and fruit flies. This ecological role underscores the chemical versatility of the bisabolene skeleton across different kingdoms of life.

3. Biosynthesis and Biochemistry

3.1 Biosynthetic Pathway

The biosynthesis of bisabolene involves three isoprene units, where one molecule of DMAPP is first condensed with one molecule of IPP by the enzyme geranyl-pyrophosphate synthase (GPPS), forming geranyl-pyrophosphate (GPP); and then a second enzyme, farnesyl-pyrophosphate synthase (FPPS), catalyses the addition of a second IPP unit to GPP, originating farnesyl-pyrophosphate (FPP). FPP is the final precursor for bisabolene biosynthesis, and its conversion into bisabolene is catalysed by the enzyme bisabolene synthase.

The mevalonate pathway converts acetyl-CoA into FPP in eight enzymatic steps: acetyl-CoA acetyltransferase (atoB), truncated HMG-CoA reductase (tHMGR), HMG-CoA synthase (HMGS), mevalonate kinase (MK), phosphomevalonate kinase (PMK), mevalonate diphosphate decarboxylase (PMD), isoprenyl diphosphate isomerase (idi) and farnesyl diphosphate synthase (ispA).

The enzyme bisabolene synthase is a dedicated terpene cyclase. This cytosolic sesquiterpenoid synthase requires a divalent cation cofactor (Mg²⁺ or, to a lesser extent, Mn²⁺) to neutralize the negative charge of the diphosphate leaving group. The enzyme is induced as part of a defense mechanism in the grand fir Abies grandis as a response to stem wounding. The expressed synthase has a deduced size of 93.8 kDa and exhibits properties typical of sesquiterpene synthases.

3.2 Biosynthetic Relationship to Other Natural Compounds

Bisabolenes are intermediates in the biosynthesis of many other natural chemical compounds, including hernandulcin, a natural sweetener. Hernandulcin synthesis begins with FPP entering the sesquiterpene pathway, followed by cyclization producing (+)-epi-α-bisabolol, with subsequent oxidation reactions catalyzed by cytochrome P450 enzymes (CYP450) leading to the final formation of hernandulcin. In conifers, a cDNA encoding (E)-α-bisabolene synthase was isolated from a wound-induced grand fir stem library and was shown to produce (E)-α-bisabolene as the sole product from farnesyl diphosphate, with the expressed synthase having a deduced size of 93.8 kDa. The olefin product bisabolene is then converted to todomatuic acid, juvabione, and related insect juvenile hormone mimics in Abies species.

3.3 Common Preparations and Forms

Bisabolene occurs naturally in plant essential oils and oleoresins, where it is most commonly encountered as a complex mixture with other volatile sesquiterpenes. Commercial preparations include:

• Essential oils: Steam-distilled fractions containing bisabolene isomers as major or minor constituents, depending on the source plant.
• Oleoresins: Particularly relevant for copaiba (Copaifera spp.), where β-bisabolene is among the dominant sesquiterpene fractions. The oleoresin of copaiba trees is extracted through tapping and is used therapeutically in its raw state or distilled to yield copaiba essential oil.
• Biosynthetically produced isolates: Due to the low concentration of bisabolene and the long harvest cycle, industrial production of this isoprenoid in plants is economically challenging. Chemical synthesis of bisabolene also suffers from significant disadvantages, such as low yields, toxic side products, and high costs.
• Microbially fermented bisabolene: Multiple research groups have engineered microorganisms to produce bisabolene in meaningful quantities. Via a combination of enzyme screening and metabolic engineering, researchers obtained a more than tenfold increase in bisabolene titers in Escherichia coli to over 900 mg/L, and also produced bisabolene in Saccharomyces cerevisiae at over 900 mg/L.

4. Traditional and Historical Use

4.1 Amazonian Traditional Medicine (Copaiba)

The most extensively documented traditional use of a β-bisabolene-containing natural product is the Amazonian copaiba oleoresin from Copaifera trees. The tree yields an oleoresin which is extensively used in local traditional medicine, mainly as an anti-inflammatory and antinociceptive agent. The traditional uses of copaiba oleoresin in the Brazilian Amazon include wound and ulcer healing, antimicrobial and anti-inflammatory properties for skin diseases, as well as relief of rheumatic diseases. The name copaiba originates from an indigenous Amazonian language (Tupi) — cupa-yba — denoting "reservoir" or "vessel," with reference to its store of oleoresin in the trunk.

Copaiba oil is used in the Amazon's traditional medicine especially as an anti-inflammatory ingredient, in ulcer healing, scarring, and for leishmaniasis. The anti-inflammatory activity has been related to sesquiterpenes, in particular β-bisabolene and β-caryophyllene. The copaiba oil has been indicated for traditional use since its approval by the Food and Drug Administration in 1972.

4.2 Middle Eastern and African Traditional Use (Opoponax / Scented Myrrh)

Opoponax (Commiphora guidottii), sometimes called "scented myrrh," has been used historically in East African and Middle Eastern cultures as a perfumery ingredient, fumigant, and therapeutic resin. The resin of Commiphora species has a centuries-long tradition as a medicinal and aromatic substance in these regions. Scientific analysis has confirmed that β-bisabolene constitutes a significant component of its essential oil. The identified major compounds of opoponax essential oil include β-bisabolene (80.99%), elemicin (8.04%), germacrene D (4.15%), and cyperene (2.82%). The historical use of opoponax in traditional pharmacopeias across Africa and the Arabian Peninsula was as a wound-healing resin, expectorant, and constituent of sacred incense.

4.3 Conifer Resins and Traditional Phytotherapy

Bisabolene-containing conifer resins (spruce and fir) have been used for centuries across Northern European, Native American, and Siberian traditions as topical wound healers and antiseptics. The wound-inducible nature of bisabolene synthase in grand fir suggests that bisabolene and related sesquiterpenes form a constitutive part of the tree's defense oleoresin, which has historically been collected and applied topically to cuts and skin infections by indigenous peoples of North America and Northern Europe.

4.4 Chamomile (Bisabolene as Precursor)

Sesquiterpenes have been known for their wide range of biological functions including anti-infective, antioxidant, anti-inflammatory, and anticancer activities and can be obtained from the Matricaria genus. Matricaria chamomilla is an herbaceous plant, cultivated in many countries for commercial, pharmaceutical, and cosmeceutical purposes. German chamomile (Matricaria recutita) has been used since antiquity in European folk medicine for gastrointestinal complaints, inflammatory skin conditions, and wound healing. Bisabolene itself is the direct enzymatic precursor to the chamomile-specific α-bisabolol, meaning that any plant preparation rich in α-bisabolol necessarily traverses the bisabolene chemical space.

5. Key Constituents, Active Compounds, and Mechanisms of Action

5.1 The Bisabolene Isomers

Three isomers are known — α-, β-, and γ-bisabolene — which differ by the positions of the double bonds. Each isomer can additionally exist as stereoisomers (R and S configurations), yielding numerous distinct stereochemical forms with potentially different biological profiles. The (E)-configuration of α-bisabolene is the primary isomer produced by conifer wound-inducible synthases.

5.2 Anti-Inflammatory Mechanisms

Based on in vitro and in vivo preclinical studies, the dominant mechanism of anti-inflammatory action for bisabolene-type sesquiterpenoids involves the downregulation of key pro-inflammatory signaling pathways. Anti-inflammatory activity of β-bisabolol in in vitro studies represented by inhibition of cytokines clearly indicates that this sesquiterpene has the property to induce downregulation of the enzymes iNOS and COX-2, which are upregulated during inflammation. α-Bisabolol can inhibit ERK and P-38 signal transmission, induce downregulation of the iNOS and COX-2 enzymes, and subsequently reduce NO and PGE₂ production in inflamed cells.

For the bisabolol-type compounds, the nuclear receptor PPAR-γ has been identified as a specific molecular target. Molecular docking and dynamic analysis revealed that α-bisabolol interacts with PPAR-γ, a nuclear receptor protein that is highly expressed in the colon epithelium. α-Bisabolol decreased the phosphorylation of activated mitogen-activated protein kinase (MAPK) signaling and nuclear factor kappa B (NF-κB) proteins, and enhanced colon epithelial PPAR-γ transcription factor expression.

5.3 Antioxidant Mechanisms

The antioxidant mechanism of α-bisabolol is mainly associated with the reduction of ROS/RNS, MDA, and GSH depletion, MPO activity, and augmentation of SOD and CAT. Experimental in vitro data on bisabolene itself supports antioxidant activity: β-bisabolene exhibited strong antioxidant activity (IC₅₀ = 14 ± 0.8 μg/mL) in the essential oil of Psammogeton canescens.

5.4 Cytotoxic / Anticancer Mechanisms

The primary cytotoxic mechanism of β-bisabolene in preclinical models is induction of apoptosis. This loss of cell viability was because of the induction of apoptosis as shown by Annexin V-propidium iodide and caspase-3/7 activity assay. For related bisabolane-type compounds, cell cycle arrest has also been reported: investigations found that certain bisabolane-type compounds inhibited yeast cell growth by controlling progression from the G1 phase to the S phase, and from the G2 phase to the M phase. Biochemical and genetic analysis showed that the compounds activated environmental stress response pathways involving Hog1 and affected Cln3/G1 cyclin activity, thus inhibiting the expression of target genes encoding SCB- and MCB-binding factors.

5.5 Antimicrobial Mechanisms

The antifungal activity of α-bisabolol was evaluated on Aspergillus fumigatus species. Results demonstrated that α-bisabolol is capable of inhibiting the growth of A. fumigatus as well as inhibiting the synthesis of ergosterol responsible for cellular membrane integrity. In the context of antibacterial drug synergy, α-bisabolol potentiated the action of tetracycline and reduced the MIC of norfloxacin to a clinically relevant concentration. The results indicate α-bisabolol is a potential substance to be used as an efflux pump inhibitor.

5.6 Biosynthetic Intermediary Role

Bisabolene has been identified as a biologically producible precursor to a diesel fuel alternative and/or cold weather additive bisabolane. Additionally, bisabolene is a metabolic intermediate in the biosynthesis of juvabione and todomatuic acid, compounds with insect juvenile hormone mimic activity, as established in grand fir biology.

6. Scientific Evidence by Area of Application

6.1 Anti-Inflammatory Activity

In vitro evidence: The in vitro anti-inflammatory activity of β-bisabolol purified from cotton gin trash (CGT) essential oil was investigated against lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages as well as 3T3 and HS27 fibroblast cell lines. Nitric oxide (NO), prostaglandin E₂ (PGE₂), TNF-α, IL-6, and IL-8 were measured. Non-toxic concentrations of β-bisabolol (1.6–50.0 µg/mL) significantly inhibited the production of inflammatory mediators in a dose-dependent manner. Maximal inhibition by β-bisabolol was 55.5% for NO, 62.3% for PGE₂, and 45.3% for TNF-α production in RAW cells. β-Bisabolol induced a level of inhibition similar to an equal concentration of α-bisabolol (50.0 µg/mL), a known anti-inflammatory agent. These results suggest β-bisabolol exerts similar in vitro effects to known topical anti-inflammatory agents and could be exploited for cosmetic and therapeutic uses.

In vivo (animal) evidence — copaiba oleoresin (β-bisabolene-rich): β-bisabolene-rich oleoresin reduced the formation of paw edema induced by carrageenan and reduced the global number of cells in the air pouch assay, as well as exudate volume and nitrite, TNF-α, IL-1β, and prostaglandin E₂ levels (p < 0.05). Oleoresin doses of 10, 100, and 400 mg/kg were tested in rats. This study supports the anti-inflammatory potential of C. reticulata oleoresin, confirming the traditional medicinal use of this natural product by local people in the Amazon region.

In vivo (animal) evidence — colonic inflammation: Treatment with α-bisabolol in DSS-administered mice significantly reduced Disease Activity Index (DAI), myeloperoxidase (MPO) activity, and colonic length, and protected the microarchitecture of the colon. α-Bisabolol treatment also reduced the expression of proinflammatory cytokines (IL-6, IL-1β, TNF-α, and IL-17A) at the protein and mRNA levels. The expression of COX-2 and iNOS inflammatory mediators were reduced along with tissue nitrite levels.

Evidence assessment: Anti-inflammatory effects of bisabolene-type sesquiterpenes are supported by multiple in vitro and animal studies. However, no controlled clinical trials in humans have been identified for bisabolene itself. Evidence remains at the preclinical stage.

6.2 Anticancer / Cytotoxic Activity

In vitro — breast cancer: β-Bisabolene, constituting 5% of the opoponax essential oil, exhibited selective cytotoxic activity for mouse breast cancer cells (IC₅₀ in normal Eph4: >200 µg/mL; MG1361: 65.49 µg/mL; 4T1: 48.99 µg/mL) and human breast cancer cells (IC₅₀ in normal MCF-10A: 114.3 µg/mL; MCF-7: 66.91 µg/mL; MDA-MB-231: 98.39 µg/mL; SKBR3: 70.62 µg/mL; BT474: 74.3 µg/mL). The selectivity index — the ratio of IC₅₀ in normal versus cancerous cells — was favorable, suggesting preferential killing of cancer cells over normal mammary epithelial cells.

In vivo — mammary tumor model: β-Bisabolene was also effective in reducing the growth of transplanted 4T1 mammary tumors in vivo (37.5% reduction in volume by endpoint). This mouse model study provides proof-of-concept for in vivo activity but is far removed from human clinical applicability.

In vitro — other tumor models: Modern studies indicated that marine nitrogenous bisabolane-type sesquiterpenoids have potent cytotoxicity. For instance, 3-isocyanotheonellin, theonellin isothiocyanate, and 7-isocyano-7,8-dihydro-α-bisabolene showed potent cytotoxicity. In separate work on oleoresin fractions from Copaifera reticulata, essential oil exhibited a cytotoxic effect, with IC₅₀ values of 16.89, 19.16, 13.08, and 19.33 µg/mL obtained for B16-F10, HepG2, HL-60, and K562 cell lines, respectively. However, β-bisabolene was inactive in all of the tested tumor cell lines in this particular study (showing IC₅₀ values greater than 25 µg/mL). This discrepancy in results across studies highlights that cytotoxic activity may be highly context-dependent — varying by cell line, isomer, and assay conditions.

Evidence assessment: Cytotoxic and anticancer effects of β-bisabolene are documented in cell culture and one animal model. No human clinical trials have been conducted. Evidence is preliminary, restricted to in vitro and rodent in vivo systems, and conflicting across different cell lines and preparations. Results cannot be extrapolated to clinical cancer treatment.

6.3 Antimicrobial Activity

Antibacterial — synergy with antibiotics: A published study (cited in the literature as Nascimento et al., 2007, in Antonie Van Leeuwenhoek) reported synergistic bactericidal activity of Eremanthus erythropappus oil or β-bisabolene with ampicillin against Staphylococcus aureus.

Antifungal: The essential oil of P. canescens (with β-bisabolene as the major constituent) was particularly active against Candida albicans and Escherichia coli, with the lowest minimum inhibitory concentration and minimum bactericidal/fungicidal concentration values. These results support the use of the EO and its main compounds for antioxidant properties and antimicrobial activity.

Anti-chlamydial: Five undescribed highly oxygenated bisabolane sesquiterpenes were isolated from whole plants of Ligularia narynensis and tested for their anti-chlamydial activity. The results show that two of these compounds inhibited the growth of Chlamydia abortus in host cells in a dose-dependent manner.

Evidence assessment: Antimicrobial properties of bisabolene-type sesquiterpenes are well-documented in vitro. These compounds have antibacterial, anti-inflammatory, antidiabetic, antifouling, and cytotoxic properties, as confirmed across multiple independent research groups. No human clinical data are available for bisabolene as a standalone antimicrobial agent.

6.4 Antioxidant Activity

β-Bisabolene exhibited strong antioxidant activity (14 ± 0.8 μg/mL) in the essential oil of Psammogeton canescens. Mechanistically, the antioxidant property of bisabolane-type compounds is linked to the reduction of oxidative stress markers including reactive oxygen species and malondialdehyde, while upregulating endogenous antioxidant enzymes.

Evidence assessment: Antioxidant activity is supported by in vitro assays. No controlled human studies are available for bisabolene specifically.

6.5 Biofuel Precursor (Non-Therapeutic Application)

A landmark study published in Nature Communications by scientists at the U.S. Department of Energy's Joint BioEnergy Institute identified bisabolane (the fully saturated hydrogenation product of bisabolene) as a promising diesel fuel alternative. The researchers identified a novel biosynthetic alternative to D2 diesel fuel, bisabolane, and engineered microbial platforms for the production of its immediate precursor, bisabolene. They identified bisabolane as an alternative to D2 diesel by measuring the fuel properties of chemically hydrogenated commercial bisabolene. Testing revealed that bisabolane's performance rating (derived cetane number) was 41.9, which is within the 40–55 range of standard diesel fuel. The "cloud point" was -78°C, better than diesel's -35°C, and vastly superior to commercial biodiesel's -3°C. In sufficient quantities, bisabolane could initially serve as a cold weather additive to diesel and biodiesel formulations, and with higher yields, could substitute for these fuels. Researchers chemically hydrogenated the biosynthetic bisabolene into bisabolane as the conversion step, meaning bisabolene itself is the biotechnological target compound, not bisabolane.

7. Body Systems and Health Areas of Association

The following body systems and health areas are associated with bisabolene-type sesquiterpenoids in the peer-reviewed preclinical literature:

• Immune system / Inflammatory response: Inhibition of TNF-α, IL-1β, IL-6, NO, PGE₂, and related inflammatory mediators; downregulation of iNOS, COX-2, MAPK, and NF-κB pathways.
• Gastrointestinal system: Demonstrated activity in colitis models (DSS-induced), consistent with traditional use of copaiba oleoresin for gastrointestinal complaints.
• Skin / Integumentary system: Numerous experimental studies demonstrated pharmacological properties of α-bisabolol including anticancer, antinociceptive, neuroprotective, cardioprotective, and antimicrobial effects. Bisabolene and its alcohol derivatives are extensively used in topical preparations for skin inflammation, wound healing, and cosmetic applications.
• Oncological research: Preclinical cytotoxicity against breast cancer, leukemia (HL-60), hepatocellular carcinoma (HepG2), and melanoma (B16-F10) cell lines.
• Infectious disease: In vitro and in vivo models showing antimicrobial activity against bacterial and fungal pathogens, including Chlamydia abortus, Staphylococcus aureus, Candida albicans, Aspergillus fumigatus, and multiple Vibrio species.
• Musculoskeletal system: Traditional use of copaiba oleoresin for rheumatic diseases, with supporting preclinical anti-inflammatory data.

8. Dosage Forms and Doses Reported in Studies

No standardized human dosage has been established for bisabolene. The following doses and concentrations appear specifically in the cited scientific literature:

• In vitro anti-inflammatory (β-bisabolol from CGT oil): Non-toxic concentrations of CGT oil and β-bisabolol (1.6–50.0 µg/mL) significantly inhibited the production of inflammatory mediators in a dose-dependent manner.
• In vivo anti-inflammatory — copaiba oleoresin (β-bisabolene-rich, rat): The anti-inflammatory potential was evaluated by carrageenan-induced paw edema and air pouch assays using oleoresin concentrations of 10, 100, and 400 mg/kg.
• In vivo acute toxicity — copaiba oleoresin (rat): The oleoresin was nontoxic at a single dose of 2000 mg/kg, showing low acute toxicity.
• In vivo antitumor — β-bisabolene (mouse): The in vivo analysis revealed tumor growth inhibition rates of 5.37–37.52% at doses of 40 and 80 mg/kg/day, respectively.
• In vitro cytotoxicity — breast cancer cell lines: β-Bisabolene IC₅₀ values for human breast cancer cell lines ranged from 66.91 µg/mL (MCF-7) to 98.39 µg/mL (MDA-MB-231).
• Microbial production titers (research/industrial context): In engineered E. coli, bisabolene titers reached over 900 mg/L, and similar titers were achieved in engineered S. cerevisiae.

These figures pertain exclusively to experimental research contexts; no therapeutic dosing guidance for human use has been established.

9. Safety Considerations

9.1 Acute Toxicity

The copaiba oleoresin rich in β-bisabolene was nontoxic at a dose of 2000 mg/kg in rats, showing low acute toxicity. For the related compound α-bisabolol, the United States Food and Drug Administration (USFDA) has considered α-bisabolol as a safe compound due to its low toxicity.

9.2 Fragrance Safety Assessment

There are insufficient direct toxicity data on bisabolene (CAS # 495-62-5). In silico evaluation was conducted to determine read-across analogs; based on structural similarity, reactivity, physical-chemical properties, and expert judgment, farnesane and α-farnesene were identified as analogs with sufficient data for toxicological evaluation. A genotoxicity read-across study using α-farnesene as the analog concluded that the compound was non-clastogenic in an in vitro micronucleus test.

9.3 Gastrointestinal Adverse Effects of High-Dose Copaiba Oil

Overall, adverse effects of copaiba are dose-related. High doses of the oil can cause gastrointestinal irritation, diarrhea, salivation, and depression of the central nervous system. At a dose of 10 g, symptoms of intolerance include nausea, vomiting, cramps, diarrhea, and rash. These adverse effects are attributable to the copaiba oleoresin as a whole and cannot be attributed solely to β-bisabolene without further isolation studies.

9.4 Limitations of Available Safety Data

The effectiveness of α-bisabolol on human health is still a question. Therefore, more clinical studies are needed to gain in-depth insight into the beneficial properties of α-bisabolol on human health. The same caveat applies with even greater force to bisabolene itself, for which direct human safety data are essentially absent from the published literature. Regulatory-grade toxicological datasets (chronic toxicity, reproductive toxicity, genotoxicity) have not been identified for bisabolene in publicly available peer-reviewed sources.

9.5 Drug Interactions

No pharmacokinetic drug interaction data for bisabolene in humans were identified in the scientific literature. The identified preclinical data concern only synergistic antimicrobial effects: α-bisabolol potentiated the action of tetracycline and reduced the MIC of norfloxacin to a clinically relevant concentration. Whether bisabolene itself would affect drug-metabolizing enzymes or efflux transporters in a clinically meaningful way in humans is currently unknown.

10. Industrial and Ecological Significance

Bisabolene is commonly used as a component of perfumes and as a precursor in chemical synthesis. Besides their currently established applications, bisabolene was also shown to be suitable for the synthesis of biofuels both for land and air transportation. In recent years, the volatile and combustible properties of sesquiterpenes inspired the development of terpene-based biofuel from bisabolene and farnesene.

Ecologically, the wound-inducibility of bisabolene synthase in conifers has implications for forest pest resistance. The olefin product of the bisabolene cyclization reaction is considered to be the precursor in Abies species of todomatuic acid, juvabione, and related insect juvenile hormone mimics. These compounds disrupt insect development, forming part of the conifer's chemical arsenal against bark beetles and other pests.

The challenge of sustainable production has driven significant biotechnological research. Archaea appear suitable producers of isoprenoids, as their membrane lipids consist of isoprenoid ethers synthesized via a variant of the mevalonate (MVA) pathway. Archaeal model species have versatile metabolic capacities, which makes them potential candidates for biotechnological applications.

11. Summary of Evidence Quality

The body of research on bisabolene and bisabolane-type sesquiterpenoids is substantial at the level of chemistry, biosynthesis, and preclinical pharmacology. Pharmacological studies indicated the biological potential of these compounds, which exhibited antimicrobial, anti-inflammatory, enzyme inhibitory, cytotoxic, antimicroalgal, and antifouling properties. However, as of the time of writing, no published controlled clinical trials in humans have been identified for bisabolene as an isolated compound or standardized preparation. Investigations into the useful biological functions of bisabolane-type sesquiterpenoids are ongoing in natural and synthetic chemistry. Evidence for anti-inflammatory and antimicrobial effects comes from in vitro cell models and rodent studies. Evidence for anticancer effects is limited to in vitro assays and one in vivo mouse model. All therapeutic claims must therefore be understood as preclinical and preliminary.

References

• Wikipedia — Bisabolene
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• Chemistry and Bioactivity of Marine-Derived Bisabolane Sesquiterpenoids: A Review — Frontiers in Chemistry
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• Identification and characterization of two bisabolene synthases from linear glandular trichomes of sunflower (Helianthus annuus L.) — ScienceDirect / Phytochemistry
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• Terpenoid-based defenses in conifers: cDNA cloning, characterization, and functional expression of wound-inducible (E)-α-bisabolene synthase from grand fir (Abies grandis) — PNAS
• Chemical composition, antimicrobial and antioxidant activities of the essential oil of Psammogeton canescens — PubMed
• Effect of α-Bisabolol and Its β-Cyclodextrin Complex as TetK and NorA Efflux Pump Inhibitors in Staphylococcus aureus Strains — PMC
• Metabolic engineering of Synechocystis sp. PCC 6803 for improved bisabolene production — PMC
• High-efficiency production of bisabolene from waste cooking oil by metabolically engineered Yarrowia lipolytica — PMC
• Biosynthesis of α-Bisabolol by Farnesyl Diphosphate Synthase and α-Bisabolol Synthase and Their Related Transcription Factors in Matricaria recutita L. — PMC / IJMS
• RIFM Fragrance Ingredient Safety Assessment, Bisabolene, CAS # 495-62-5 — Elsevier FMSR
• Alternative Diesel Fuel From Biosynthetic Bisabolene — Federal Laboratory Consortium
• Developing Thermosensitive Metabolic Regulation Strategies in Saccharomyces cerevisiae to Enhance α-Bisabolene Production — ACS Synthetic Biology