Table 2. GC-MS quantitative analysis of the hydrolyzable constituents identified in cutin samples purified using either cholinium hexanoate or BMIM acetate in 2-, 15-, or 170-h reactions

The reference cutin and the feedstock (i.e. untreated peels) were also analyzed for comparison. Results are given as wt % (n = 3). The identification yields (wt %) and the mass of the nonhydrolyzable fraction (recalcitrance [%]) are indicated.

Compound NameCompound Abundances
Untreated FeedstockReference CutinCholinium HexanoateBMIM Acetate
2 h15 h170 h2 h15 h170 h
wt %
Fatty acids2.60 ± 0.131.52 ± 0.241.27 ± 0.150.88 ± 0.130.67 ± 0.091.96 ± 0.20.74 ± 0.10.10 ± 0.06
  Hexadecanoic acid1.25 ± 0.040.74 ± 0.050.64 ± 0.040.41 ± 0.110.33 ± 0.030.63 ± 0.050.42 ± 0.030.10 ± 0.06
  Octadeca-9,12-dienoic acid0.43 ± 0.150.23 ± 0.050.20 ± 0.030.11 ± 0.010.74 ± 0.12
  Octadec-9-enoic acid0.24 ± 0.060.11 ± 0.020.09 ± 0.040.18 ± 0.03
  Octadecanoic acid0.91 ± 0.120.31 ± 0.100.09 ± 0.000.13 ± 0.050.12 ± 0.020.18 ± 0.040.13 ± 0.06
  4-Oxocyclohexane-1-carboxylic acid0.23 ± 0.080.14 ± 0.120.22 ± 0.060.23 ± 0.000.19 ± 0.02
Dicarboxylic acids10.89 ± 1.0818.38 ± 0.4418.64 ± 0.4919.2 ± 2.1618.64 ± 0.5818.45 ± 1.1919.3 ± 0.219.99 ± 2.05
  Nonanedioic acida0.43 ± 0.020.26 ± 0.020.26 ± 0.150.36 ± 0.010.27 ± 0.020.22 ± 0.04
  Hexadecanedioic acid0.56 ± 0.021.51 ± 0.071.30 ± 0.071.52 ± 0.101.22 ± 0.081.47 ± 0.071.42 ± 0.150.46 ± 0.07
  8/9-Hydroxyhexadecanedioic acidb10.33 ± 1.0616.43 ± 0.3817.08 ± 0.5517.43 ± 2.0117.06 ± 0.5016.7 ± 1.1417.66 ± 0.209.53 ± 0.23
ω-Hydroxy acids11.13 ± 0.3515.04 ± 0.3118.42 ± 0.6317.42 ± 2.2217.69 ± 1.2818.95 ± 0.418.49 ± 1.0622.90 ± 1.68
  16-Hydroxyhexadecanoic acid5.38 ± 0.168.17 ± 0.218.20 ± 0.128.50 ± 0.658.32 ± 0.218.35 ± 0.238.48 ± 0.3915.71 ± 0.68
  16-Hydroxy-10-oxohexadecanoic acid3.02 ± 0.282.29 ± 0.146.39 ± 0.526.21 ± 0.976.28 ± 0.616.81 ± 0.056.62 ± 0.391.80 ± 0.12
  9, 10-Epoxy-18-hydroxyoctadecanoic acid1.14 ± 0.241.93 ± 0.091.73 ± 0.071.63 ± 0.381.27 ± 0.321.67 ± 0.131.60 ± 0.142.38 ± 0.53
  9, 10-Epoxy-18-hydroxyoctadecenoic acid1.60 ± 0.152.65 ± 0.202.10 ± 0.251.62 ± 0.181.82 ± 0.552.11 ± 0.091.79 ± 0.183.01 ± 0.59
Polyhydroxy acids55.05 ± 2.0165.06 ± 0.6561.67 ± 0.2862.49 ± 4.0663.01 ± 1.9260.64 ± 1.6961.47 ± 1.2867.01 ± 1.44
  10,16-Dihydroxyhexadecanoic acidc53.22 ± 2.2363.24 ± 0.9858.83 ± 0.4259.68 ± 5.0361.20 ± 2.1658.12 ± 1.8958.97 ± 1.5563.12 ± 2.42
  9,10,18-Trihydroxyoctadecanoic acid1.00 ± 0.110.94 ± 0.061.11 ± 0.321.19 ± 0.670.53 ± 0.000.85 ± 0.110.90 ± 0.131.51 ± 0.45
  9,10,18-Trihydroxyoctadec-12-enoic acid0.84 ± 0.390.89 ± 0.361.73 ± 0.071.63 ± 0.381.27 ± 0.321.67 ± 0.131.60 ± 0.142.38 ± 0.53
Sterolsd20.33 ± 1.07
  Identification yield (%)56.38 ± 2.4650.7 ± 2.3858.1 ± 0.8859.34 ± 6.6356.39 ± 1.2058.02 ± 2.4560.35 ± 3.4682.15 ± 0.20
  Recalcitrance (%)22.14 ± 2.9813.32 ± 1.3928.3 ± 4.9827.47 ± 0.5833.07 ± 0.5619.75 ± 0.3620.21 ± 1.0618.15 ± 2.48
  • a This compound was overestimated or overlapped with an unknown compound.

  • b This compound was associated with the possible presence of unspecific isomers.

  • c The major species of this compound was 10,16-diOH and minor species were 9,16- and 8,16-diOH.

  • d Triterpenoids and sterols identified were β-amyrin (5.69 ± 0.44), α-amyrin (4.44 ± 0.20), δ-amyrin (7.53 ± 1.48), and stigmasterol (2.68 ± 0.49).