*4.7. Analyses of GC and GC–MS*

(*Z*)-citral, (*E*)-citral, (*S*)-citronellal, and (*R*)-citronellal were determined by GC (Agilent 6890N) equipped with an FID detector and chiral capillary BGB-174 column (BGB Analytik, Böckten, Switzerland, 30 m × 250 μm × 0.25 μm). The flow rate and split ratio of N2 as the carrier gas were set as 1.38 mL/min and 1:100, respectively. Both injector and detector were kept at 250 ◦C. The column temperature program was listed as follows; initial temperature of 90 ◦C for 25 min, 20 ◦C/min ramp to 150 ◦C for 3 min, and 30 ◦C/min ramp to 180 ◦C for 3 min. The injection volume was 1 μL. The retention times of (*S*)-citronellal, (*R*)-citronellal, (*Z*)-citral, and (*E*)-Citral were 22.459 min, 23.067 min, 29.164 min and 30.398 min, respectively (Figure S3).

(*S*)-citronellal, (*R*)-citronellal, (*Z*)-citral, and (*E*)-Citral were validated through GC–MS analysis (Figure S4). The GC–MS analysis (Agilent7890A/5975C, Agilent Technologies Inc., Santa Clara, CA, USA) comprised the following parameters; auxiliary heating zone temperature, 250 ◦C; MS quadrupole temperature, 150 ◦C; ion source temperature, 230 ◦C; scan quality range, 30–500 amu; emission current, 200 μA; and electron energy, 70 eV.
