Artemisia abrotanum, L.

Muangphrom, Paskorn, Misaki, Momoka, Suzuki, Munenori, Shimomura, Masaya, Suzuki, Hideyuki, Seki, Hikaru & Muranaka, Toshiya, 2019, Identification and characterization of (+) - α-bisabolol and 7 - epi-silphiperfol- 5 - ene synthases from Artemisia abrotanum, Phytochemistry 164, pp. 144-153 : 145

2.1. Sesquiterpenoid profile of A. abrotanum

Sesquiterpenoid profiles of two different strains of A. abrotanum were analyzed. GC-MS analyses of n- hexane extracts of the aerial parts of A. abrotanum revealed 15 sesquiterpenoids, tentatively identified based on comparisons of retention indices and mass spectra with those of authentic compounds and reference data ( Fig. S1 and Table 1 ; Adams, 2007). β- Caryophyllene, germacrene D, bicyclogermacrene, and silphiperfolane-type sesquiterpenoids have been previously identified in A. abrotanum ( Obistioiu et al., 2014; Radulovi ć et al., 2009; Wang et al., 2018), whereas detection of β- and δ- elemenes, α- and βcopaenes, and α- humulene in this study is the first report of these compounds in A. abrotanum . Among all detected compounds, tricyclic silphiperfol-5-en-3-one A occupied 60% of the total sesquiterpenoid content of the extract. This finding strongly supported that the as yet unidentified gene encoding silphiperfolene synthase is highly expressed in the A. abrotanum used in this study.

Figures

Fig. 1. Proposed biosynthetic pathways of silphiperfol-5-en- 3-one A and (+)-α-bisabolol in A. abrotanum. The enzymes responsible for each step are indicated with arrows. The full names of the enzymes are given in the text. Determined biosynthetic pathways in this study are highlighted in bold. The α-bisabolol oxide A, detected by Radulović et al. (2009) and the previously reported sesquiterpene synthase synthesizing triquinane α-isocomene (MrTPS2; Irmisch et al., 2012) are also included. Dot arrows indicate a multi-step conversion.