 | |
| Names | |
|---|---|
| IUPAC name (1R,2R,5E,9Z)-1,5,9-trimethyl-12-propan-2-yl-15-oxabicyclo[10.2.1]pentadeca-5,9-dien-2-ol | |
| Identifiers | |
3D model (JSmol) | |
| ChemSpider | |
| |
| |
| Properties[1] | |
| C20H34O2 | |
| Molar mass | 306.490 g·mol−1 |
| Density | 1.0±0.1 g/cm3 |
| Boiling point | 408.9±45.0 °C at 760 mmHg |
| Vapor pressure | 0.0±2.2 mmHg at 25°C |
Refractive index (nD) | 1.493 |
| Hazards | |
| Flash point | 160.7±23.0 °C |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Incensole is a C20diterpenealcohol and biomarker for some plants of theBoswellia genus. It, along with itsacetate ester incensole acetate, is an abundant component offrankincense, theresin collected fromBoswellia trees.[2] Incensole is usedarchaeologically to assist in identifying trade routes and distinguishing the identity offrankincense from otherresins which may have been used together inincense and othersalves. Incensole has also been deemed to be an active component in medicinalfrankincense.[2]
Incensole was first isolated in 1966 at theUniversity of Rome's Institute of Organic Chemistry by S. Corsano and R. Nicoletti while investigating the neutral components ofBoswellia carteri resin.[3] There was some controversy as to whether the sample analyzed by S. Corsano and R. Nicoletti was actually fromB. carteri and some believed that the original sample was from aB. papyrifera specimen. Further testing done by H. Obermann in 1977 identified an "Eritrea" typeB. carteri sample (so named because it originated from theEritrea region) which displayed incensole levels consistent with those found by Corsano and Nicoletti, but the sample specimen was likelyB. papyrifera misidentified asB. carteri.[4] In 2005, incensole was used as a biomarker forfrankincense (also known asolibanum) in order to determine the composition of Ancient Egyptian mummification balms andunguents,[5] speaking to its role in studying the history of religion.
Oily in appearance, incensole has lowvolatility. It can be synthetically prepared fromcembrene,[6] aterpenoid, and cembrenol (serratol), its biologic precursor.[6]Diterpenes andterpenoids are classes of biomarkers which are synthesized in plants and have been found in insects,[7] possibly because of accumulation of terpenoids within their diets.[8][page needed]Terpenoids have gained special interest due to their potential asanti-inflammatories, chemotherapies, andantiparasitics.[7]
It has been proposed that incensole is produced inBoswellia plants via serratol fromgeranylgeranyl pyrophosphate (GGPP),[4] a C20 precursor for many metabolic branches such as thechlorophyll,carotenoid, andgibberellin biosynthetic pathways.[9] To begin, GGPP loses itspyrophosphate group enabling it to be 1,14-cyclized to formcembrene after the loss of a proton.Cembrene is thenhydrolyzed to form serratol which in turn undergoesepoxidation and intramolecularcyclization to form incensole.[4] Though this has been used to make incensole synthetically,[6] the abundances of incensole, serratol, incensole acetate, and iso-serratol inBoswellia species known to produce incensole are inconsistent with what would be expected if this pathway occurredin situ.[4]
Incensole is mainly found in theresin ofBoswellia trees which grow in a region across Northern Africa fromEthiopia toNigeria.[10]Boswellia trees prefer to grow in arid, stony regions,[10] and cuts to the body of the trees seepfrankincenseresin which hardens and darkens when exposed to the air.[citation needed] Incensole is a biomarker offrankincense from certainBoswellia species; these species areB. papyrifera,B. occulta, B. carteri,B. sacra,[5][11][12][13] and possiblyB. serrata though there are conflicting results as to whether it really produces incensole.[4]B. carteri andB. sacra have been determined to actually be the same species, except thatB. carteri is native to Africa whileB. sacra is native toSouth Arabia.[4]
It has also been proposed that incensole and incensole acetate can be derived from other sources such as these:[4]
Gas chromatography and mass spectrometry were used to identify incensole in these specimen, but to conclusively identify these species as producers of incensole/incensole acetate, isolation and structural elucidation from these species would have to occur.[4]
Incensole was originally isolated in 1966 by S. Corsano and R. Nicoletti using several ether extractions and vacuum separations, and then characterized usingUV-Vis,IR, andH-NMR spectroscopy. They found incensole to have noUV-Vis absorption above 210 mμ.[3] The distinguishingIR andH-NMR peaks of incensole are reported in the tables below,[3] and the observedmass spectrum of incensole from a study done in 2014 onfrankincense in incense pots is pictured to the right.[14]
| Wave Number (cm−1) | Peak Identity |
|---|---|
| 3620 | -OH |
| 1670 | C=C |
| 1375, 1390 | CH3-C-CH3 |
| 1050 | C-O |
| Chemical Shift (ppm) | Protons[15] | Group Identity |
|---|---|---|
| 0.90 | (d, 6H, J = 6.5 c/s) | isopropyl |
| 1.02 | (s, 3H) | CH3-C-O |
| 1.48, 1.61 | (s, 3H) | CH3-C= |
| 3.18 | (d, 1H, J = 10 c/s) | HC-OH |
| 5.06 | (2H, broad signal) | CH3CH=C(CH3)2 |
Incensole is most often extracted bychromatographic extractions andhydrodistillations, which produce afrankincense essential oil. Incensole is typically characterized byGC/MS althoughthin layer chromatography andnear-infrared spectroscopy.[16][4]
Unfortunately, within some of the earlier literature,frankincense biomarker compositions have been misattributed to differentBoswellia species, as was seen in the mistaken attribution of the first extraction of incensole being from aB. carteri specimen when it likely came from aB. papyrifera specimen. This is likely because the taxonomic certifications forfrankincense bought from market as opposed to collected straight from the tree are often faulty or absent.[4]
Frankincense has been used for thousands of years in religious ceremonies and for medicinal purposes.[2] In fact, by tracing incensole's degraded products, historians have been able to use it to understand the historical use ofincense in religion. In one such case, the examination of incensole as a biomarker led to the identification of certain porous pots buried in medieval, Belgian, Christian graves as incense burners. Further study indicated that thoughfrankincense was a main component of funeraryincense at the time, other, cheaper local resins were mixed into theincense, possibly to reduce cost.[14]
Additionally,frankincense has been used for thousands of years as medicine. It is listed in texts such as thePapyrus Ebers and the Syriac book of medicine and was prescribed by the practitionersCelsus andCulpepper as a remedy for a variety of ailments from stomach ulcers and gastrointestinal hemorrhages togout and open wounds.[13] Modern analysis on the medicinal efficacy offrankincense has revealed incensole and incensole acetate, along withboswellic acids, to be the bioactive ingredients of frankincense.[2]
Due to its religious and medicinal significance,frankincense and its biomarker components, like incensole, can be found all over the world in Europe, Asia, the Mediterranean, and the Middle East[2][13][17] as the result of global trade.
Previously, thetherapeutic properties offrankincense had been attributed toboswellic acids within theresin, but research from 2019 and 2020 has found incensole and its acetate ester to be major contributors tofrankincense'stherapeutic efficacy.[2] This research has found incensole to act as an anti-inflammatory andneuroprotective compound aftermurine head-trauma on top of exhibitinganxiolytic, anti-depressive, andsedative effects in mice.[2]
It is proposed that incensole works as an anti-inflammatory through the inhibition of theNF-κB pathway which is responsible for the increased production of proinflammatory proteins. Insensitivity in theNF-κB pathway is correlated toarthritis,asthma,inflammatory bowel disease,ataxia telangiectasia, cancers, andneurodegenerative diseases.[2][12][18]
It has also been found that incensole acetate activates theTRPV3 channel[2] which is responsible for regulating wound healing and the perception of pain and itching, among other things.[19] It is thought that this is another key component of incensole's role as an anti-inflammatory agent.
Incensole has also been cited as a potential antibacterial againstBacillus.[12]
