The Boswellia carteri frankincense trees are famously variable, so much so that they’ve been confusing botanists and taxonomists for centuries–and there is still debate today about whether the species is the same as Boswellia sacra or not!
The essential oil of B. carteri resin is similarly variable, with many different combinations of alpha-pinene, alpha-thujene, limonene, sabinene, myrcene, d-3-carene, and more.
Recently, we analyzed 42 samples of oil from B. carteri trees in Somaliland and Puntland. By running the oil compositions through a hierarchical cluster analysis, we have identified the major chemotypes and sub-chemotypes of B. carteri:
1. Methoxydecane chemotype (30-60% methoxydecane)
2. Alpha-Thujene Chemotype (up to 40% alpha-thujene)
3. Alpha-Pinene Chemotype, with three sub-chemotypes:
1. Alpha-pinene with moderate limonene
2. Limonene with moderate alpha-pinene
3. Alpha-pinene, sabinene, myrcene, and limonene in approximately equal levels
The variability of this oil contrasts with the stability of other species such as Boswellia papyrifera, which is always composed of high octyl acetate and moderate octanol, or Boswellia serrata, which is dominated by alpha-thujene. Why is B. carteri so variable? What are the factors driving chemotype? These questions will form the next stage of chemical ecological research.
An interesting point to note is that despite the variability, the Boswellia carteri chemotypes are distinct from B. sacra chemotypes from Oman and Yemen–proving that there is a distinct African chemotype and scent profile, unique to Somaliland and Somalia.
See the full paper here: https://onlinelibrary.wiley.com/doi/10.1002/cbdv.201800047