C7 c30 saturated alkanes standard solution

The sesquiterpene biosynthesis precursor [5,5-²H₂]-1-deoxy-ᴅ-xylulose (d₂-DOX) was synthesized according to Meyer et al. [39 (link)], while [6,6,6-²H₃]-(±)-mevalonolactone (d₃-MVL) was purchased from C/D/N Isotopes Inc. (Pointe-Claire, Quebec, Canada). Retention indices were calculated using a C₇–C₃₀ saturated alkanes standard solution obtained from Sigma-Aldrich (St. Louis, MO, U.S.A.).
The analytical standard (+)-valencene (purity: 80.0%) was also acquired by Sigma-Aldrich (St. Louis, MO, U.S.A.). Guaiazulene (purity: 99.8%) was purchased from Alfa Aesar (Ward Hill, MA, U.S.A.). Water for dilutions was purified using a Milli-Q water purification system (Merck Millipore, Billerica, MA, U.S.A.). Parafilm^® M was purchased from Sigma-Aldrich (St. Louis, MO, U.S.A.) to seal the sample vials to prevent the possible evaporation of volatile analytes.

The following plant metabolites used in our study were ordered: (−)-caryophyllene oxide, (+)-nootkatone, zerumbone, β-amyrin, crocetin dialdehyde, saffron stigma (Sigma-Aldrich, St. Louis, MO, USA), α amyrin (Carl Roth, Karlsruhe, Germany) and taraxasterol acetate (Biorbyt, Cambridge, UK) (Figure 1). All compounds were dissolved in dimethyl sulfoxide (DMSO) in order to be used in the assays. Saffron threads were incubated in DMSO for 1 h on a rotary shaker (100 rpm); then, the supernatant was collected and used in the work. A C₇-C₃₀ saturated alkanes standard solution was also obtained from Sigma-Aldrich to calculate the GC retention indices of the sesquiterpenes formed by A. thaliana. The liquid standards used were β-elemene, ordered from Abcam plc (Cambridge, UK) and (−)-trans-caryophyllene (sum of enantiomers, purity: ≥98.0%) and (−)-α-cedrene (sum of enantiomers, purity: 96.4%) purchased from Sigma-Aldrich.