Last week, as part of my series in supporting one’s desire for a calmer and more enjoyable holiday, I began my journey down decoding the Boswellia bewilderment that many encounter when choosing a frankincense oil to use. Due to marketing by specific manufactures, consumers are often confused by the various types available. I realized that just offering the benefits of frankincense oil without providing guidance on the different species may create more stress. This two-part series is intended to guide you into more clarity around making this important decision to help soothe your soul.
In this article, I’m going to dig a little more into the science for those who want the details on the differences and strengths of the most well-known species. It is a summary of my exciting findings among the 299 results of interesting research studies on Boswellia from Science.gov. I was sucked into reviewing in depth several of the first 101 studies and skimmed over the abstracts of the less relevant ones.
The Beautiful Tapestry of Molecules Found in the Boswellia Species
Below are some highlights of my favorite findings and my summaries on this emotionally, physically, and spiritually enhancing essential oil that can make any holiday more calm and bright!
First, a few things to keep in mind from Part I:
- There are about 25 species in the Boswellia Differences of constituents in frankincense are related to the region in which it is found and its chemotype. (see table)
- You must consider quality and seek out an ethical supplier. Much of the frankincense oil on the market is often mislabeled, either intentionally or unintentionally.
Now I will discuss more of the chemistry and biology of Boswellia. In a review paper, the authors highlighted the findings of several studies that reported the differences found in some of the most common varieties, even among the same species. I provided a snippet to the complexity of this in Part I, but let me now break this down for you even more. For an overview, you can click here for the reviews’ table entitled “Percentages of major compounds in the essential oils of reported Boswellia species.”
Warning for those who are bottom-liners…
- This is the time for those who are only seeking the take-home points to skip to the conclusion.
- For the science lovers and essential oils’ fanatics, read on.
The Nitty Gritty of the Monoterpene and Sesquiterpene Alphabet Soup of the Most Popular Frankincense Oil Species
1. Boswellia Sacra and Boswellia Carterii
(Note: There is B. carteri and B.carterii referenced in the literature. Are these different species or an author’s spelling preference? I was unable to find a conclusive answer. Does anyone have research on this?)
The Complicated Science
These two oils are often confused and may be labeled/used interchangeably; however, differences have been found in chemical makeup with further investigations. Although some believe that they are just different varieties of the same species with different chemotypes, one abstract reports statistical differences. When the authors analyzed with optical rotation the Somalian (B. carterii) and Omani/Yemeni (B. sacra) species, these essential oils’ compositions were revealed. It stated (bold highlight mine):
Components identified with their average percent for B. sacra are a-thujene (0.6%), a-pinene (68.2%), camphene (2.1%), sabinene (2.9%), B-pinene (2.0%), myrcene (0.7%), limonene+B-phellandrene (6.2%). Components identified with their average percent for B. carterii are a-thujene (7.9%), a-pinene (37.3%), camphene (0.8%), sabinene (4.9%), B-pinene (1.8%), myrcene (7.3%), limonene+B-phellandrene (14.4%). Initially, GC-MS analysis did not reveal major statistical differences. However, optical rotation values, B. Sacra (+30.1°) and B. carterii (-13.3°), demonstrated a greater significant difference. Enantiomeric ratio (+)/(-) values of a-pinene for B. sacra and B. carterii are 8.24 and 0.68, respectively, were also calculated aiding our conclusion that B. sacra and B. carterii are not synonymous but rather two distinct and individual frankincense species. (source)
According to this review paper, these variations found in Boswellia sacra and B. carterii may be the result of genetically determined differences of monoterpene synthesis.
The essential oil of B. carterii and B. sacra and showed that…
B. carterii can always be identified by the key markers viridiflorol, cembrenol, dimethyl ethermorcinol, and most importantly incensole…
B. sacra was distinguished by higher quantities of a-pinene and delta-3-carene, while B. carterii possessed higher quantities of a-thujene, myrcene, limonene, trans-B-caryophyllene, germacrene D, and incensole… (bold highlighting mine)
Lindsey Elmore, essential oils pharmacist, stated in her blog that B.carterii contains more incensole diterpenes and “lower amounts of limonene, myrcene, alpha-thujene.” B. Sacra is overwhelmingly a-pinene with incensole.
According to her “…incensole acetate interacts with the body and found that it activates certain receptors called the TRPV-3 receptor. This can make carterii feel warm on the skin and interact with different brain channels which produce feelings of calming and spiritual exaltation.” (source)
I then found another article that also reported differences found in these two species; with alpha-pinene higher in B.sacra than in B. carterii (two i’s):
Chemical differentiation of Boswellia sacra and Boswellia carterii essential oils by gas chromatography and chiral gas chromatography-mass spectrometry.
Major botanical and scientific references currently identify two species of frankincense, Boswellia carterii and Boswellia sacra, as being synonymous. We evaluated the Somalian (B. carterii) and Omani/Yemeni (B. sacra) species by chemical analyses to determine if there were any minor or major differences between the two species of frankincense. Components identified with their average percent for B. sacra are a-thujene (0.6%), a-pinene (68.2%), camphene (2.1%), sabinene (2.9%), B-pinene (2.0%), myrcene (0.7%), limonene+B-phellandrene (6.2%). Components identified with their average percent for B. carterii are a-thujene (7.9%), a-pinene (37.3%), camphene (0.8%), sabinene (4.9%), B-pinene (1.8%), myrcene (7.3%), limonene+B-phellandrene (14.4%). Initially, GC-MS analysis did not reveal major statistical differences. However, optical rotation values, B. Sacra (+30.1°) and B. carterii (-13.3°), demonstrated a greater significant difference. Enantiomeric ratio (+)/(-) values of a-pinene for B. sacra and B. carterii are 8.24 and 0.68, respectively, were also calculated aiding our conclusion that B. sacra and B. carterii are not synonymous but rather two distinct and individual frankincense species. (source)
Notice something missing? While this was only an abstract, in another preliminary investigation, it was stated that B. carteri had three main varieties and there was also no mention of incensole in the abstract:
Frankincense, the oleo-gum resin of Boswellia species, has been an important element of traditional medicine for thousands of years. Frankincense is still used for oral hygiene, to treat wounds, and for its calming effects. Different Boswellia species show different chemical profiles, and B. carteri, in particular, has shown wide variation in essential oil composition. In order to provide insight into the chemical variability in authentic B. carteri oleoresin samples, a hierarchical cluster analysis of 42 chemical compositions of B. carteri oleo-gum resin essential oils has revealed at least three different chemotypes, i) an ?-pinene-rich chemotype, ii) an ?-thujene-rich chemotype, and iii) a methoxydecane-rich chemotype. (source)
Now, this full study reported that Boswellia sacra definitely had no incensole as stated right in the abstract:
Abstract: The yield of hydrodistillation of a botanically certified Oleogum Resin of Boswellia sacra essential oil (5.5%); and its chemical constituents were determined. The GC/MS technique was used for the analysis of the oil. Several oil components were identified based upon comparison of their mass spectral data with those of reference compounds published in literature or stored in a computer library. The oil was characterized by the high content of the monoterpenes (34) which constituted 97.3% in which E-?-ocimene and limonene were the major constituents. The remaining 2.7% was accounted for the sesquiterpenes (16) in which the E-caryophyllene was the major constituent. The analysis proved the complete absence of the diterpenes. (source)
The Take Home Point on These Two Species of Frankincense
It appears that both of these oils contain high monoterpenes which have a variety of benefits, including the phytoncides (pinenes). You will need to check with your supplier as to whether your specific brand contains incensole.
2. Boswellia serrata
In one review, this oil is reported to have high levels of a-thujene, a monoterpene:
Analyzing B. serrata by hydrodistillation, Singh et al. , Verghese et al. , and Camarda et al.  each found a-thujene to be the dominant substance. However, the specific values were in the range 22.7–61.4% (source)
Another article found similar results, with variations existing based on whether the oil was a commercial preparation or from the wild habitat. The wild habitat contained more oxygenated monoterpenes and sesquiterpenes. (source)
Yet another source reported constituents very similar to B. carterii, which makes me question labeling errors, and chemotypes.
3. Boswellia frereana
One study reported that this oil was high in terpenes.
Another states, “The composition of the essential oil of Boswellia frereana was investigated by GC/MS. Ten terpenes were identified and p-cymene was by far the most abundant component of the oil.” (source)
Are You Confused Yet?
I’ve taken you through all this literature and here we are, ending up in a chemical soup of confusion with no definitive answer!
Welcome to good science.
We don’t just cherry pick studies that support our claims, but deliberately look for inconsistencies to prove ourselves wrong!
The truth is, essential oils in general have many benefits, regardless of species and this chemical soup. This is because there is an array of complex and interrelated factors that determine which constituents are present in the bottle of oil you hold.
Considerations include the quality of the essential oil, the climate it was exposed to, harvesting practices, seasonal variations, the distillation process, your body’s specific biochemistry, and more. All of these aspects will combine to determine the chemotype, or the secondary metabolites that predominate in the essential oil. I summarized most of these caveats here and how brands may differ here. This could explain the mass confusion found in research studies attempting to verify the predominant constituents.
A complicated, scientific way of saying this and summarizing the constituents found in these popular species was said brilliantly in the review:
Although a-pinene was the major compound and found in high concentrations in all grades of Omani frankincense (B. sacra) , this compound cannot be considered as a chemotaxonomic marker for B. sacra because of its frequent occurrence in other species of Boswellia (Table 2). Frankincense is a natural oleo-gum resin whose ingredients may depend on many factors, such as location, climate, time of harvest, and other environmental conditions. An indication of this variance could be clearly seen when comparing the different results of the samples of the same species (Table 2). A remarkable diversity of the predominant compounds in similar Boswellia species reported by different authors is clearly seen in Table 2. For example myrcene and a-thujene were individually reported to be major compounds for B. serrata. Mikhaeil et al.  reported duva-3,9,13-triene-1a-ol-5,8-oxide-1-acetate to be a major compound in the essential oil of B. carteri whereas Basar  found octyl acetate to be a major compound for the same species. Limonene, a-pinene, and octanol were reported individually to be major constituents for B. rivae. The incompatibility between the results mentioned in different literature could still be logical due to the influence of several factors mentioned earlier such as the climate, harvest conditions, and geographical source. However, such contradicting results make it difficult to rely on the chemical profile of the oil as a chemotaxonomic marker to distinguish between the different commercial varieties of frankincense. (source)
We have traveled through the literature and there is more than enough evidence to verify that there are many species of frankincense. (source) Variations in compounds exist even among them due to a complexity of quality factors and location of the plants. This means, first and foremost, you want to trust your supplier and their sourcing methods when selecting a frankincense oil to purchase.
The metabolites present may differ just enough for specific effects. For example, if you definitely want more of the brain boost along with calming and immune support, you may want to go with B. carterii for its higher incensole acetate. For more chillin’, perhaps B. sacra.
You also want to evaluate your own body’s response to the frankincense you are using because everyone’s biochemistry may need something a little different. I previously covered the importance of an individual’s biochemistry and the interaction of other environmental and lifestyle factors to consider when selecting which essential oil to use. You can read a summary here.
Bottom Lining It for Science Geeks and for All Who STILL Care
If you are a biochemistry genius and can decipher the constituents, verify the quality of the oil, and trust the supplier, you’ll probably get more benefit than someone else grabbing the nearest frankincense bottle.
Yet, let’s go back again to the main point in part I: there are enough beneficial compounds in a good quality frankincense oil for your body to benefit.
This is based on evidence of the overall body support of the terpenes, the neurological and physically enhancing sesquiterpenes, the diterpenes found in some species of some brands, and the calming and immune building phytoncides that are present in most species.
As I stated in my most recent video summary, we all can benefit from any good quality frankincense oil.
Since this is so long, I will give you some time to take it in and digest it.
Next week, I will post the video summary that brings together all the important take-home points on this topic. I will also provide a list of additional resources on the actions of the major constituents reported in the most popular species of frankincense… for those who STILL want to dig into more of the science.
This material is for information purposes only and is not intended to diagnose, treat, or prescribe for any illness. You should check with your doctor regarding implementing any new strategies into your wellness regime. These statements have not been evaluated by the FDA. (Affiliation link.)
Disclaimer: This information is applicable ONLY for therapeutic quality essential oils. This information DOES NOT apply to essential oils that have not been tested for purity and standardized constituents. There is no quality control in the United States, and oils labeled as “100% pure” need only to contain 5% of the actual oil. The rest of the bottle can be filled with fillers and sometimes toxic ingredients that can irritate the skin. The studies are not based solely on a specific brand of an essential oil, unless stated. Please read the full study for more information.