Frankincense Revisited, Part I: Comparative Analysis of Volatiles in Commercially Relevant Boswellia Species

Abstract

The genus Boswellia comprises many species which are famous for their production of frankincense, a fragrant gum resin. In the published literature, manifold studies on the volatiles and semivolatiles in individual samples of these gum resins exist, yet very few studies have investigated multiple samples. Contradictory results with regard to the volatile composition exist in literature. In this first part of the study, a large sample set (n = 46) of mostly commercially obtained gum resins and essential oils was investigated by solid-phase microextraction gas chromatography/mass spectrometry. A total of 216 compounds were identified or tentatively identified from the four commercially relevant species, namely B. sacra, B. serrata, B. papyrifera, and B. frereana, and the statistical evaluation of the resulting chemical profiles allowed a clear distinction between the species by their volatile profile. With only few exceptions, the designated species was found to be in accordance with the composition reported in reliable literature sources and detected in botanically identified samples. Chemotaxonomic marker substances were suggested to facilitate the differentiation of commercial gum resins or essential oils based on their volatile profile.

Frankincense Revisited, Part II: Volatiles in Rare Boswellia Species and Hybrids

“…part I of this study), to which it otherwise bears the closest resemblance. Boswellia ‐specific diterpenes like incensole and serratol were not detected in this sample (see also ). The low content in monoterpenes is probably due to the low sample size (<< 1 g), which might lead to a quick evaporation of the more volatile compounds.…”

“…Boswellia elongata showed the highest β ‐myrcene 31 content compared to all other samples, including those from part I. Another interesting feature is the identification of m ‐ (1.7%) and p ‐camphorene (0.6%), 255 and 258 , which are typically found in samples of B. serrata . The analogy does, however, not extend any further, since B. elongata totally lacks the phenylpropanoid compounds of B. serrata .…”

“…Several unusual sesquiterpenes were detected in this sample in traces, such as longifolene 171 (0.1%), longicyclene 154 (0.4%), and α ‐longipinene 149 (0.5%). These compounds have not been reported for Boswellia species, except as potential adulteration indicators , and are typically found in Pinaceae resins . It is not possible to conclude from a single sample if these compounds are actually true constituents or just a contamination during processing, for example, from the distillation process.…”

“…Missing compound numbers in the tables account for compounds found in part I of the study, and are intended to maintain consistent compound numbering in both parts. For a full list of retention indices as well as a list of unidentified compounds and their mass spectral data, please refer to the supporting information of part I .…”

“…The instruments, methods, and procedures for the investigation of the gum resin and essential oil samples are identical to the ones reported in part I of this publication . A brief summary is given here: powdered gum resin samples were extracted with a 50/30 μm divinylbenzene/carboxen/polydimethylsiloxane SPME fiber (DVB/CAR/PDMS, 1 cm fiber length, by SUPELCO , Bellefonte, PA, U.S.A.) at 80 °C for 30 min after a 30 min equilibration period.…”