## 3 Materials and Methods
### Chromatography Methods and Compound Identification (GC-MS and NMR Analysis)  
In several cases hydrodistilled essential oils were studied. Prior to GC-MS analysis the essential oils were dried to remove hydrosol emulsions using anhydrous sodium sulphate (Na\({}_{2}\)SO\({}_{4}\)) powder (0.5 g in 10 mL essential oil) for at least 24 h. Afterwards, essential oils were dissolved in dichloromethane (CH\({}_{2}\)Cl\({}_{2}\)) at a ratio of 1:1000. If a single leaf extraction was performed, a small fragment of leaf, approximately 100-500 mg, was extracted with CH\({}_{2}\)Cl\({}_{2}\) for analysis by GC-MS.  
Analyses were performed using a HP 6890 gas chromatograph coupled with a HP 5973 mass spectrometer detector. An autosampler unit (HP 7673-100 positions) was used to perform the 1 \(\mu\)L injections. Separation was accomplished with a HP-5 MS column (30 m by 0.25 mm, i.d., 0.25 \(\mu\)m phase thickness). Operating conditions were as follows: injector: split ratio 25:1; temperature: 250 \({}^{\circ}\)C; carrier gas: helium, 1.0 mL/min, constant flow; column temperature, 60 \({}^{\circ}\)C (no hold), 5 \({}^{\circ}\)C per minute then @ 280 \({}^{\circ}\)C hold for 4 min. A second method was used for solvent extracts, 50 \({}^{\circ}\)C (no hold), 5 \({}^{\circ}\)C per minute then @ 280 \({}^{\circ}\)C hold for 20 min. MS was acquired at 70 eV using a mass scan range of 45-400 \(m/z\). Quantification was based on the peak areas on the chromatogram generated by MS data (total ion chromatogram). Integration parameters were set to exclude peak areas less than 0.5%.  
Most identification of volatile organic compounds was performed by comparison of mass spectra with the NIST electronic library database [56] and confirmed using calculated retention indices relative to n-alkanes, then compared to published values. A second library in the form of a book by [PERSON] [57] was used to resolve any further discrepancies with identification. Most samples were injected once only, accept in cases of unusual or unexpected chemical profiles. Several of the components were identified by isolation (10% ethyl acetate, 90% hexane, normal phase column chromatography using silica gel) and comparison of respective \({}^{13}\)C NMR spectra to published values, using a 500 MHz Bruker Avance (Germany) spectrometer in \(d\)-chloroform. These were: anymol [58], \(t\)-murotol [59], freelingnite [60], ngaione [13], epingaione and dehydrongaione and dehydroepingaione [15], myoporone and dehydromyoporone [18], myodesmone and isomyodesmone [61], myomontanone [62], eremoacetal [63], methoxymyodesert-3-ene [12], 1S-acetoxymyodesert-3-ene [16], myodesert-1-ene [3], mitchellenes G and B [4], 9-hydroxydendrolasin (listed as 6-hydroxydendrolasin in literature) [46], oppositifolic acid (as 5-acetoxymethyltetradeca-trans-2,trans-4,trans-6-trienoic acid) [48], germacrene-D-4-ol (listed as 1,6-germacradien-5-ol) [64], eremophilone and santalcamphor and 9-hydroxy-7(11),9-eremophiliden-8-one [7]. These components (Figure 9) were authenticated bymatching \({}^{1}\)H or \({}^{13}\)C NMR spectra to published values (citations given in brackets). See Supplementary A2 and B for NMR spectra; see Supplementary A1 and A4 for MS data; for images of compounds, see Supplementary A3 for more structures or Figure 9 for the most relevant to the current study.  
Figure 9: Uncommon or new sesquiterpenes isolated from species of Eremophila and assigned in the current study.