Sesquiterpenes olibanum

The first observation is the similarity between the chemical compositions of both the Boswellia carteri and Boswellia sacra. For these three olibanum samples, a-pinene (2), (3-myrcene (8) and limonene (14) are the predominant monoterpenes. p-Caryophyllene (73) is the major sesquiterpene besides a-copaene (65), a-humulene (also called a-caryophyllene) (78) and caryophyllene oxide (95). The characteristic olibanum compounds isoincensole and isoincensole acetate (128) together with cembrene A (120) are the main diterpenes. 

Boswellia serrata olibanum has a chemical composition close to that of both the B. carteri and of B. sacra, but contains compounds that are absent in those from other Boswellia and could be used as markers methylchavicol (38), p-anisaldehyde (47), methyleugenol (70), isocaryophyllene (82), sesquiterpene 91, elemicin (92) and an unidentified diterpene (124) eluting between cembrene C (123) and verticilla-4(20),7,ll-triene (125). It is devoid of (5-caryophyllene (73), a-humulene (78), caryophyllene oxide (95) and bornyl acetate (50). 

B. frereana and B. papyrifera olibanum have very different terpenic composition from the others. B. frereana olibanum contains the same monoterpenes as olibanum from B. carteri, B. sacra or B. serrata, but is very poor in sesquiterpenes and contains none of the diterpenic biomarkers cited before. Two unidentified compounds (55 and 56) seem to be specific and the main diterpenes, present in high level, are four dimers of a-phellandrene. Dimer 3 (113) is the major component. On account of its absence in the other olibanum samples, it can be considered as characteristic of B. frereana olibanum. 

The chemical composition of B. papyrifera olibanum is markedly different from that of other Boswellia, with small amounts of monoterpenes and sesquiterpenes, large amounts of w-octanol (18) and -octy I acetate (40), with the latter being the major compound, and the presence of particular diterpenes [incensole (127), incen-sole acetate (129), incensole oxide (130) and incensole oxide acetate (131)] and the absence of both isoincensole and isoincensole acetate (128). Linear carboxylic acids from hexanoic acid (10) to lauric acid (93) were also identified in B. papyrifera olibanum exclusively. 

Eight olibanum samples of unknown botanical origin have been analysed [26]. The chemical compositions are summarized in Table 10.3 for three of them. Both the olibanum coming from Somalia and that from a market in Ta izz (Yemen) have been attributed to Boswellia carteri or sacra on the basis of the occurrence of the characteristic diterpenes isoincensole and isoincensole acetate (128) together with diterpene 126. The absence of methylchavicol (38), oxygenated sesquiterpene 91 and diterpene 124 and the presence in relatively large amount of (3-caryophyllene (73), ot-humulene (78) and caryophyllene oxide (95) excluded the hypothesis of a B. serrata sample. 

Figure 10.8 Total ion current chromatograms obtained after headspace SPME for (a) Kyphi and (b) B. sacra olibanum. Peak labels correspond to compound identification given in Table 10.3. The occurrence of isoincensole acetate (128) as well as the occur rence of the oxygenated sesquiterpene 98 and of dimer 2 (111) in Kyphi are clear fingerprints of the botanical origin of the olibanum used. Peaks labelled by letters correspond to the following compounds a, cinnamaldehyde b, vanilline c, curzerene d, furanoeudesma 1,3 diene e, a santalol f, 2 methoxyfuranodiene. Reproduced from S. Hamm, j. Bleton, j. Connan, A. Tchapla, Phytochemistry, 66, 1499 1514. Copyright 2005 Elsevier Limited...

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